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How indoor air quality in schools affects student learning and health

Some U.S. schools are using federal relief funds to improve indoor air quality amid the COVID-19 pandemic. If you’re covering the issue, it’s important to know what the research says about how air quality can affect student health and achievement.

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by Denise-Marie Ordway, The Journalist's Resource April 12, 2023

This <a target="_blank" href="https://journalistsresource.org/education/indoor-air-quality-schools-student-learning-health/">article</a> first appeared on <a target="_blank" href="https://journalistsresource.org">The Journalist's Resource</a> and is republished here under a Creative Commons license.<img src="https://journalistsresource.org/wp-content/uploads/2020/11/cropped-jr-favicon-150x150.png" style="width:1em;height:1em;margin-left:10px;">

This collection of research on indoor air quality in U.S. schools, originally published in December 2022, was updated April 12 with a new report that raises concerns about the number of school districts that have not followed the federal government’s guidance on strategies to increase indoor airflow and ventilation to prevent the spread of COVID-19.

The COVID-19 pandemic has forced a spotlight on indoor air quality in schools and the importance of proper ventilation.

It also has brought renewed attention to a longstanding problem in many U.S. classrooms: air pollution, ranging from pet dander and paint fumes to mold, trace metals and formaldehyde.

For many years, schools facing funding shortfalls put off costly projects that would improve indoor air quality and ventilation — replacing roofs, for example, and updating their heating and air conditioning systems. When the federal government announced in 2021 that it would distribute $123 billion in emergency relief funds to help schools prevent the spread of COVID-19 and recover from its impact, school districts had backlogs of deferred renovation and maintenance.

Education officials have a lot of flexibility in how they use that money, the bulk of which remained unspent in late 2022, according to a Washington Post analysis . School districts have until September 2024 to spend the money.

Public health leaders, researchers and advocacy organizations have urged them to put some of it toward improving indoor air quality. Meanwhile, the CDC has stressed that improved air flow and ventilation are crucial in helping stop COVID-19 from spreading indoors.

On April 7, the CDC released a report indicating many school districts have not adopted any of the four key strategies it recommended for increasing air flow and ventilation, including inexpensive changes such as opening windows and using fans to circulate air.

To better understand schools’ efforts to improve indoor air quality amid the pandemic, the private firm MCH Strategic Data surveyed a total of 8,410 school districts nationwide late last year.

Epidemiologist Miguella Mark-Carew , the lead author of the report, said journalists should ask school district leaders about barriers that might be preventing them from improving indoor air quality. She also recommended asking officials about their experiences implementing changes.

“For school districts that have implemented ventilation improvements, understanding lessons learned from their ventilation improvements may help others school districts at the beginning stages of making such improvements,” Mark-Carew wrote in an email interview. “Learning about how improving indoor air quality has impacted students, teachers, and staff (i.e., reduced staff and student absenteeism) would also provide information about the benefits of proper ventilation.”

As news outlets scrutinize schools’ use of emergency relief funds and cover the progress of these projects, it is important journalists know what the research says about how indoor air quality can affect student health and learning.

Children are especially susceptible to health problems linked to poor air quality.

“Exposure to various air pollutants in school buildings risks severe damage to pupils’ health since they inhale a larger volume of air corresponding to their body weights than do adults,” a group of 19 researchers write in an October 2022 paper, “ Indoor Air Quality and Health in Schools: A Critical Review for Developing the Roadmap for the Future School Environment .”

Below, we’ve gathered and summarized several academic studies and government reports that examine this issue in the U.S. and abroad. Together, they suggest:

• Tens of thousands of U.S. schools have been operating with faulty or outdated HVAC systems, and many schools lack air conditioning.
• Poor indoor air quality and ventilation are common in schools across the planet.
• Certain pollutants often are found in higher levels inside school buildings than in homes and commercial buildings.
• Poor indoor air quality is linked to a variety of health problems, ranging from coughing and wheezing to more serious conditions such as asthma and cancer.
• Breathing polluted air harms students’ academic performance. If students get sick, they miss school. Studies also show that poor classroom air quality reduces cognitive ability.
• Remediation efforts are hampered by the fact there are “no generally accepted criteria for distinguishing a problematic level of dampness and mold, which adversely affects health, from a non-problematic level of dampness and mold,” one researcher writes.
• Improvements in outdoor air quality over the years has helped boost student test scores, raising the possibility that cleaner air could help reduce historic differences in test scores between Black and white children.
• Climate change has created new challenges for schools, considering some airborne pollutants are more prevalent in warmer climates. As temperatures rise, some schools in cooler regions of the country have installed air conditioning.

Read more about these findings below. Toward the bottom of the page, we’ve included links to other useful resources, including investigative journalism projects focusing on indoor air quality in schools.

The condition of school facilities

Ventilation Improvements Among K-12 Public School Districts — United States, August-December 2022 Miguella Mark-Carew; et al. Morbidity and Mortality Weekly Report, April 2023.

When 8,410 U.S. school districts were asked about indoor air quality since the COVID-19 pandemic began, many reported using at least one of these strategies the CDC had recommended for improving airflow and ventilation inside classrooms and other buildings:

• Replacing or upgrading HVAC systems.
• Maintaining continuous airflow in school buildings during active hours.
• Installing or using in-room air cleaners with high-efficiency particulate air (HEPA) filters.
• Installing ultraviolet germicidal irradiation (UVGI) devices.

The majority of districts, however, reported they did not use any of the four strategies — or did not know whether any had been implemented in 50% or more of their public schools, according to this report from the U.S. Centers for Disease Control and Prevention. For example, 27.9% of schools surveyed in the Midwest indicated they had not replaced or upgraded their HVAC systems. Another 39.8% reported it was “unknown” whether most schools had done that.

“That none of the four ventilation strategies was reported by more than approximately one half of school districts underscores the ongoing opportunity to improve indoor air quality among K-12 school buildings in the United States,” the authors write.

Between Aug. 8 and Dec. 29, MCH Strategic Data surveyed school district office staff members. It conducted weekly telephone surveys of districts serving 2,500 students or more, and biweekly surveys of smaller districts. 

The resulting report provides a broad look at some of the ways education officials have tried to prevent the spread of COVID-19 among students, school employees and the many people who visit or do business with local schools. It also indicates some schools could not or would not make inexpensive changes such as opening windows and using fans to keep indoor air moving.

Among the districts that did make changes, 50.7% reported maintaining continuous airflow through school buildings during active hours at most of their schools and 33.9% reported replacing or upgrading HVAC systems at most schools. Meanwhile, 28% reported installing or using in-room air cleaners equipped with HEPA filters and 8.2% reported installing UVGI devices.

The authors of the report point out that rural districts reported replacing or upgrading HVAC systems and using in-room air cleaners less frequently than districts in other areas.

“This difference might be due to limitations in resource availability and difficulty finding contractors available and willing to complete capital improvements,” they write. “In addition, rural schools might be more likely to use natural ventilation, such as opening windows, than are suburban and city schools because of less exposure to noise and air pollution in rural areas or simply having windows that can be opened.”

School Districts Frequently Identified Multiple Building Systems Needing Updates or Replacement U.S. Government Accountability Office report, June 2020.

An estimated 41% of U.S. school districts need to update or replace HVAC systems in at least half their schools, which means at least 36,000 public schools are operating with faulty or outdated HVAC systems, according to this report the U.S. Government Accountability Office prepared for Congress.

The report spotlights a range of problems common in public school buildings nationwide that can affect student learning, health and safety. The findings are based on a nationally representative survey of school districts conducted in late 2019 as well as in-person visits to 55 schools in six states — California, Florida, Maryland, Michigan, New Mexico and Rhode Island — from June to September 2019.

Some of the other big takeaways:

• 27.7% of districts reported needing to repair or replace roofs in at least half their schools. Moisture from leaky roofs “can lead to the growth of mold, fungi, and bacteria; the release of volatile organic compounds; and the breakdown of building materials,” according to the National Institute for Occupational Safety and Health . “Moisture also provides a favorable environment for cockroaches, rodents, and dust mites.”
• 8.9% need to address “environmental conditions” such as mold, lead or asbestos in at least half their schools.
• 20.6% of districts need to update or replace systems for monitoring indoor air quality in at least half their schools.

Site visits revealed that schools in cooler areas of the country have had to alter class schedules or install air conditioning systems as climates have warmed.

“Officials in a Michigan [school] district said about 60 percent of their schools do not have air conditioning, and in 2019, some temporarily adjusted schedules due to extreme heat,” according to the report. “Officials in a Maryland district said the district retrofitted some schools with air conditioning, but did not update pipes and insulation serving the HVAC systems, which has caused moisture and condensation problems in these buildings. Officials were concerned the moisture and condensation could lead to air quality and mold problems, but said that to remedy these issues could cost over $1 million for each building.”

The Ventilation Problem in Schools: Literature Review William J. Fisk. Indoor Air, November 2017.

Ventilation rates in classrooms across the globe often do not meet minimum standards, concludes this paper from the Berkeley Lab , a U.S. Department of Energy laboratory managed by the University of California.

Ventilation rates refer to the amount of outdoor air allowed into a building. In the U.S., a commonly used ventilation standard for classrooms calls for a minimum ventilation rate of approximately 7 liters per second or 15 cubic feet per minute per occupant, explains senior scientist William J. Fisk .

In this paper, Fisk reviews the scholarly literature published from 1995 to 2016 on school ventilation and carbon dioxide levels in classrooms across various countries, including the U.S., China, Greece and Sweden. He asserts that the cost of boosting classroom ventilation rates is small compared to the benefits in terms of student health and academic performance.

“The evidence of an association of increased student performance with increased ventilation rates is compelling,” he  writes. “There is evidence of associations of reduced respiratory health effects and reduced student absence with increased ventilation rates.”

Fisk points out that schools’ energy costs would rise if they improved the ventilation in their classrooms. Many schools also would need to upgrade or repair their HVAC systems.

“The economic value of increases in student performance and health and of reductions in absence are not easily quantified,” Fisk writes. “However, the annual incremental energy and capital costs of increasing ventilation rates as needed to meet or exceed current standards, range from a few dollars to about ten dollars per person.”

How common is mold and other types of indoor air pollution?

Ventilation Improvements Among K–12 Public School Districts — United States, August–December 2022 Miguella Mark-Carew; et al. Morbidity and Mortality Weekly Report, April 2023.

“That none of the four ventilation strategies was reported by more than approximately one half of school districts underscores the ongoing opportunity to improve indoor air quality among K–12 school buildings in the United States,” the authors write.

The resulting report provides a broad look at some of the ways education officials have tried to limit the spread of COVID-19 among students, school employes and the many people who visit or do business with local schools. It also confirms that some school districts could not or would not make inexpensive changes such as opening windows and turning on fans to keep indoor air moving.

Asthma Prevalence and Mold Levels in US Northeastern Schools Evin J. Howard, et al. Journal of Allergy and Clinical Immunology: In Practice, March 2021.

Researchers analyzed dust samples collected from 32 schools in densely populated areas in the northeastern U.S. and found they contained several types of mold. They also discovered mold levels in classroom dust often exceeded levels of mold found in dust collected from local homes.

Researchers tested samples taken from a total of 114 classrooms and the bedrooms and living rooms of 33 homes from 2014 through 2018. They tested for 30 types of mold, 26 of which are associated with water damage and 10 of which are associated with outdoor sources.

Classrooms had higher levels of these molds, associated with water damage: aureobasidium pullulans , eurotium amstelodami and penicillium crustosum .

Classrooms also had higher levels of these molds, associated with outdoor sources: alternaria alternata , cladosporium cladosporioides 1 , cladosporium cladosporioides 2 , cladosporium herbarum , epicoccum nigrum and penicillium chrysogenum .

For most remaining mold types, differences were not statistically significant .

When the researchers looked for links between mold levels and rates of asthma among schoolchildren living in the area, they found asthma was most common in schools with higher levels of outdoor mold — the kind found in soil and on leaf surfaces, for example.

“Therefore, the differences in the prevalence of asthma was not indicative of any significant differences in mold growth resulting from water-damage indoors but rather factors associated with the increased levels of molds from outside entering and accumulating in the schools,” the researchers write, adding that 30 of the 32 schools studied did not have air conditioning.

“In addition to AC, the frequency of window and door opening could also affect the levels of [outdoor] molds,” they write. “Cleaning frequency and thoroughness could also affect the build-up of [outdoor] molds inside schools.”

Association Between Allergen Exposure in Inner-City Schools and Asthma Morbidity Among Students William J. Sheehan, et al. JAMA Pediatrics, January 2017.

This study, which also focuses on the northeastern U.S., found high levels of mouse allergen in 37 elementary schools. It concludes that children with asthma exposed to high levels of mouse allergen, which is present in the urine, hair and dander of mice, were more likely to experience increased asthma symptoms and poorer lung function.

Researchers analyzed samples of dust taken from the classrooms and bedrooms of 284 students, aged 4 to 13 years, who had been diagnosed with asthma and attended one of the 37 elementary schools from March 1, 2008, to Aug. 31, 2013. Researchers tested for allergens associated with mice, rats, dogs, cats, cockroaches and dust mites.

Mouse allergen was most prevalent. It was detected in 99.5% of school samples and 96% of home samples. However, mouse allergen levels were higher in schools than in homes.

Cat, dog and dust mite allergens also were common in schools and homes, although at much lower levels. For example, researchers found cat allergen in 94.8% of school samples and 79.4% of home samples. Allergens from cockroaches and rats “were mostly undetectable” in both locations, the researchers write.

They note that allergen levels and the types of allergens present in schools differ according to the climate of the area.

“In the inner-city schools in our study, mouse allergen was the predominant exposure, whereas levels of cockroach, pet, and dust mite allergens were undetectable or low,” they write. “In contrast, other cities with warmer climates and different building conditions have demonstrated high levels of school cockroach allergen. The low levels of dust mites and cockroach in our study are likely owing to the long, dry, and very cold winters in the studied region, as these pests require humidity and warmth to survive.”

Classroom Indoor PM2.5 Sources and Exposures in Inner-City Schools Aleshka Carrion-Mattaa, et al.Environment International, October 2019.

For this study, researchers went into 32 schools in densely populated areas in the Northeast to measure airborne levels of fine particulate matter with diameters of 2.5 micrometers or smaller (PM2.5). Prior research has found this type of air pollution is associated with cognitive impairment and exacerbated asthma.

Researchers analyzed PM2.5 levels inside schools each fall, winter and spring from 2009 to 2013 and compared them to outdoor levels. They learned that indoor and outdoor concentrations of PM2.5 were comparable, “demonstrating penetration of outdoor pollution to indoors.” They also learned PM2.5 levels inside schools varied by season and contained a range of pollutants from automobiles, roads, soil, burning vegetation and other sources.

Pollution from motor vehicles was greatest during the fall and winter, the researchers write.

“Activities in the school environment during winter such as using motor equipment/vehicles to clean the snow and spreading salt, and during the fall such as cleaning the leaves may have driven these differences to the other sources,” they explain. “In addition, higher contribution of biomass burning in winter is more likely associated with wood burning at the neighborhood of schools.”

Of the 32 schools studied, four had air conditioning systems, 15 had radiant heat “natural ventilation” and the rest had either classroom-based vents or a combination of ventilation types.

Indoor air quality and child health, student performance

Indoor Air Quality and Health in Schools: A Critical Review For Developing the Roadmap for the Future School Environment Sasan Sadrizadeh, et al. Journal of Building Engineering, October 2022.

This paper summarizes 50 years of classroom air quality research conducted in 40 countries across six continents, concluding that various pollutants pose severe risks to student health.

Indoor air quality in schools “is characterized by a complex of contaminants,” including molds, bacteria, volatile organic compounds, particulate matter, and trace metals from road traffic, the researchers write. They note that several studies have found that levels of certain airborne pollutants were higher inside schools than in homes and commercial buildings.

“Inhalation exposure to air pollution has increased children’s mortality rate, acute respiratory disease, and asthma,” they write. “Due to different responses of the children’s immune systems to indoor air exposures, various chronic diseases and symptoms have been reported and characterized as ‘sick building syndrome.’”

This paper is based on a review of 304 reports and research papers published between 1970 and 2022. It offers a broad overview of research examining types of pollutants. It finds, for example, that volatile organic compounds — a group of chemicals used in finishing and furnishing — are one of the most dangerous pollutants found in classroom air.

“Construction materials, furnishings such as desks and shelves, resins of wood products, adhesives, glues, paints, cleaning chemicals, and carpets are primary [volatile organic compounds] emission sources in schools,” the researchers write. “The VOC concentrations in newly built or recently renovated school buildings may be significantly higher than ordinary ambient levels.”

The paper also discusses factors that influence levels of pollution inside schools such as ventilation, temperature, outdoor wind speeds and classroom cleaning protocols.

The researchers point out that research demonstrates a link between indoor air quality and student achievement. Studies “confirm that poor air quality affects both typical schoolwork of pupils, i.e. performance in simple learning tasks such as math and language exercises and pupils’ examination grades and end-of-the-year results,” they write.

Does Dampness and Mold in Schools Affect Health? Results of a Meta-Analysis William J. Fisk, Wanyu R. Chan and Alexandra L. Johnson. Indoor Air, November 2019.

While research suggests students are at an increased risk of developing respiratory issues when dampness and mold are present in schools, renovations aimed at eliminating dampness and mold do not always alleviate such health problems, according to this Berkley Lab analysis.

To better understand the health conditions associated with mold and dampness in schools, researchers combined and analyzed data they collected from 11 studies of the issue published between 1995 and 2016. What they learned: The evidence most strongly suggests that coughing, wheezing and nasal symptoms are associated with mold and dampness in schools.

When the Berkley Lab researchers reviewed four other studies on renovations to correct dampness and mold in schools, they found mixed results. One of those studies reported improvements in some — but not all — student health symptoms after a thorough renovation was completed. For example, there was not a statistically significant change in the number of student complaints about headaches. That study, which focuses on four schools in Finland, also found that “a partial renovation did not significantly improve health.”

Berkley Lab researchers note that efforts to reduce dampness and mold might be more successful is there were generally accepted criteria for distinguishing problematic levels of dampness and mold.

“Ideally, school districts seeking to reduce dampness and mold in their buildings would have clear criteria defining the dampness and mold conditions that trigger remedial actions,” the researchers write. “However, the various studies cited have employed a variety of definitions for dampness and mold and there are no generally accepted criteria for distinguishing a problematic level of dampness and mold, which adversely affects health, from a non-problematic level of dampness and mold.”

Association between Traffic-Related Air Pollution in Schools and Cognitive Development in Primary School Children: A Prospective Cohort Study Jordi Sunyer, et al. PLOS Medicine, March 2015.

Children who attended schools in parts of Barcelona, Spain where there were high levels of automobile traffic pollution showed less progress on cognitive exams than did children attending schools where traffic pollution was low, this study finds.

For example, students in more polluted areas demonstrated a 7.4% increase in working memory over the course of a year, on average. Meanwhile, students in less polluted areas showed an average increase of 11.5%.

Researchers note there also were gender-based differences.

“Boys appeared more susceptible to air pollution, although both boys and girls showed an adverse association of school air pollution with cognitive development,” they write. “Although results could be due to chance, in animals, males were more susceptible to airborne metals than females, which may be because of sex-specific altered dopamine function.”

Thirty-nine schools participated in the study. A combined 2,715 students aged 7 to 10 years took computerized tests every three months for a year so researchers could measure their inattentiveness and development of working memory.

The researchers also collected data on levels of three types of pollutants — carbon, nitrogen dioxide and ultrafine particles — present inside classrooms and outside in school courtyards.

The researchers point out that air pollution was highest in a wealthy area of Barcelona and that most of the schools in high-traffic areas that participated in the study are located there. Children attending schools where traffic pollution was lowest tended to have better-educated mothers, more siblings and fewer behavior problems than children attending schools in more polluted regions. 

The researchers suggest the harms of air pollution could stay with children years into the future.

“Impairment of high cognitive functions has severe consequences for school achievement,” they write. “Thus, reduced cognitive development in children attending the most polluted schools might result in a disadvantage in mental capital, which may have a long-lasting life course effect.”

Outdoor air pollution

Air Pollution and Student Performance in the U.S. Michael Gilraine and Angela Zheng. National Bureau of Economic Research working paper, May 2022.

Improvements in outdoor air quality over the past two decades have raised student test scores, according to this analysis, which also concludes cleaner air would help reduce longstanding differences in test scores between Black and white children.

To investigate the relationship between air quality and student achievement, the authors analyzed satellite-based measurements of fine particulate matter, or PM2.5, and other pollution-related data from 2002-03 to 2018-19. They then linked air quality data to math and reading test scores for more than 11,000 U.S. school districts for the academic years 2008-09 through 2017-18.

The authors also factored in schools’ proximity to power plants and year-to-year variations in production at individual plants. 

They determined that concentrations of fine particulate matter dropped nationwide over the period studied, driven largely by reductions in coal use. For students, on average, PM2.5 concentrations dropped by 3 micrograms per cubic meter.

The authors point out that test scores, measured in standard deviations , rose, although not as much as they could have.

“Substantial improvements to student performance and equity through cleaner air are still possible, however,” they write.

Other resources for journalists

• The U.S. Environment Protection Agency provides reports and resources on indoor air quality in schools, including national air-quality standards for particulate matter .
• The Indoor Air Quality Scientific Findings Resource Bank , located at the Berkeley Lab, gathers research on how indoor air quality affects people’s health or work performance.
• ASHRAE , formerly known as the American Society of Heating, Refrigerating, and Air-Conditioning Engineers, is a professional organization with a mission of “serv[ing] humanity by advancing the arts and sciences of heating, ventilation, air conditioning, refrigeration and their allied fields.”
• The Indoor Air Program at the University of Tulsa conducts research on indoor air quality in schools, homes and workplaces.

News investigations of indoor air quality in schools

• Toxic PCBs Festered at This Public School for Eight Years as Students and Teachers Grew Sicker , The Seattle Times and ProPublica, 2022.
• Mold Notebook: Which SC Colleges Had the Most Mold Reports , The Daily Gamecock and The Post and Courier, 2022.
• Toxic City: Sick Schools , The Philadelphia Inquirer, 2018.
• Toxic Schools: Mold, Air Quality Spark Thousands of Complaints in Central Florida , Orlando Sentinel, 2010.

About The Author

Denise-Marie Ordway

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How Does Indoor Air Quality Impact Student Health and Academic Performance?

• The presence of dampness and mold increase the risk of asthma and related adverse respiratory health effects in homes by 30-50 percent.
• There is evidence that modest changes in room temperature affect student's abilities to perform n tasks requiring mental concentration...
• Schools without a major maintenance backlog have a higher average daily attendance (ADA) by an average of 4 to 5 students per 1,000 and lower annual drop out rate by 10 to 13 students per 1,000.
• Children in classrooms with high outdoor air ventilation rates tend to achieve higher scores on standardized tests in math and reading than children in poorly ventilated classrooms.

Learn more: Frequently asked questions about Indoor Air Quality and Student Performance.

Recent research suggests that a school’s physical environment also can play a major role in academic performance, including:

• Leaky roofs;
• Problems with heating, ventilation and air conditioning systems (known as HVAC systems);
• Insufficient cleaning or excessive use of cleaning chemicals; and
• Other maintenance issues.

These can trigger a host of health problems — including asthma and allergies — that increase absenteeism and reduce academic performance. Research links key environmental factors to health outcomes and students’ ability to perform. Improvements in school environmental quality can enhance academic performance, as well as teacher and staff productivity and retention. To learn more, read the Quick Reference Guide for Student Health and Academic Performance . (PDF)

• The latest scientific data on indoor environmental quality, health and academic performance.
• Examples of school districts that have successfully coordinated and integrated IAQ maintenance and health programs to provide evidence from the field.
• Recommendations on what you can do to help you move forward towards a better indoor environment for your school.
• Indoor Air Quality Homepage
• Indoor Air Quality in Schools Homepage
• Learn about IAQ in Schools
• IAQ Tools for Schools Resources
• On-Demand Training Webinars
• Understanding IAQ Benefits
• Healthy School Renovations
• Connecting and Networking
• Frequently Asked Questions
• Publications

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Tackling air pollution and climate change together – an impact case study

Recognizing the value of SEI York’s work integrating air pollution and climate change mitigation , the University of York’s Environment and Geography Department included it as an impact case study in its REF2021 submission. Read about this work, which helped the department become ranked as one of the best of its kind for research impact.

Photo: Jonathan Jobs / Getty Images 

SEI has a partnership with the University of York  and SEI’s York centre   sits within the University’s Environment and Geography Department  (EGD). This work by SEI York’s air pollution team   was submitted by the department as one of three impact case studies for the 2021 Research Excellence Framework  (REF) exercise and contributed to the department being ranked second for impact in Earth Systems and Environmental Sciences in the Times Higher Education  REF 2021 ranking.

SEI is proud to contribute to the University of York’s continuing reputation for research with impact  that makes a positive difference to communities around the world.

Air pollution and climate change are closely linked. The sources of health-damaging air pollutants and climate-warming greenhouse gases are often the same, including transport, industry, households, agriculture and waste. In addition, a subset of pollutants, short-lived climate pollutants (SLCPs), directly contribute to both issues. SLCPs include black carbon (or soot), which contributes to particulate matter air pollution and warms the atmosphere. Methane is the second largest contributor to climate change behind carbon dioxide, and contributes to the formation of tropospheric ozone, a toxic air pollutant.

These two links mean that there is a substantial opportunity to design plans, strategies and policies which achieve global climate change goals and benefits for local air pollution and public health simultaneously. As part of the Paris Agreement of 2015, governments from over 190 countries have developed Nationally Determined Contributions (NDCs) – climate action plans outlining each country’s commitment to dealing with climate change. 

Understanding the extent of the impact of SLCPs, and knowing how to reduce them, is key to helping governments formulate research-driven climate plans and put them into practice, bringing us all closer to reaching the international climate change targets. Studying the global impact of SLCPs also provides insights into the impact these air pollutants have on human health.

The research

Since 2012 SEI York has worked at the forefront of research into SLCPs. Working with organizations including the Climate and Clean Air Coalition ( CCAC  ), United Nations Environment Programme ( UNEP  ) United Nations Development Programme ( UNDP  ), and NDC Partnership  , SEI York researchers have supported approximately 25 countries to increase their capacity to reduce SLCPs. 

As part of this work, SEI extended the existing planning tool LEAP   (Low Emissions Analysis Platform system) to assess the impacts on human health and climate change mitigation strategies.

SEI has delivered bespoke training to government officials, academics and NGOs in partner countries on the development of integrated air pollution and climate change mitigation assessments. Training and supporting local organizations to undertake such assessments demonstrates, often for the first time, the extent of health issues caused by exposure to air pollution, as well as the impact of SLCPs on climate change. It also helps identify possible solutions to reduce these impacts. SEI supports the integration of these assessments into national planning processes, so that the assessment can inform decision making and target setting.  

SEI York has also produced significant assessments of the global impacts of air pollutants on premature births and annual asthma emergency room visits. Following the 2015 revelations that car manufacturers had been using software which deliberately misled regulatory testing, SEI York were the first to publish a study to quantify the effects of hidden excess nitrogen oxide emissions from diesel vehicles.

The outcome

SEI York’s research has supported multiple policy and planning processes in partner countries. In advance of the COP26 UN Climate Conference  in November 2021, 17 countries were supported by SEI York to submit more ambitious climate change plans that included actions on SLCPs. Ten countries, with support from SEI York, have also developed National Action Plans to reduce SLCPs, which have been endorsed at a Ministerial or Cabinet level.   

In addition to these impacts on national government policy and practice, research by SEI York has provided robust evidence to back calls for strengthening global and regional climate responses. One project alone was cited in 94 policy documents from around the world, including by the UN’s Intergovernmental Panel on Climate Change ( IPCC  ) and the World Health Organization ( WHO  ). 

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Read more about SEI’s work on air pollution in our feature for the International Day of Clean Air for blue skies 2022   .

• Visit the University of York webpage

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The importance of clean air in classrooms—during the pandemic and beyond

Subscribe to planet policy, michael gilraine michael gilraine assistant professor, department of economics - new york university.

October 28, 2020

The COVID-19 pandemic has brought about an increased focus on public health, particularly in school settings. From social distancing to testing regimes, education leaders are making serious changes to ensure that schools are safe for students, staff, and teachers. As the school experience continues to be reinvented, research points to an overlooked but potentially critical factor when thinking about reopening: air quality. While we have known for some time about the negative effects of air pollution on child health , recent evidence indicates that pollution also has detrimental effects on student learning. In turn, these relationships suggest the potential for some highly cost-effective interventions to raise student performance—and keep kids safer during the pandemic.

Evidence on the Effects of Pollution on Cognition

To date, most research has linked pollution to student learning using variation in outdoor air pollution. Researchers (see here and here ) have documented significant declines in test scores when students take tests on days with high levels of particulate pollution. Another study compared students attending schools downwind relative to upwind of highways and found that increased air pollution from being downwind lowered test scores and raised behavioral incidents and absences. Similarly, in a recent working paper , a co-author and I use year-to-year variation in power production combined with wind direction to show that pollution from coal-fired power plants lower students’ test scores.

Several recent papers have been able to link indoor air quality to reduced cognitive performance. Research from chess tournaments found that a player’s probability of making an erroneous chess move (as determined by a chess engine) increased when particulate matter at the tournament venue was higher. An economist at the London School of Economics also linked indoor air quality to test performance . To do so, he collected air particulate readings in exam rooms at a university in London. He found that exam rooms at the university varied considerably in terms of air quality, and that students performed worse when they were assigned to exam rooms with higher levels of air pollution.

Reducing Children’s Pollution Exposure

Naturally, this evidence should spur policymakers to reduce children’s exposure to airborne pollutants. In general, the news has been positive on this front, with the average exposure to airborne pollutants in the United States declining by almost a third since 2000, according to satellite- and ground-based measures. These improvements have been driven by environmental regulations such as the Clean Air Act , along with the striking decline in coal use due to cheaper and cleaner alternatives, especially natural gas.

While the improvements in ambient air quality are commendable, children are also exposed to high levels of airborne pollutants indoors. Indoor air quality is a result of complex interactions between local meteorology, surrounding structures, and building characteristics (e.g., building ventilation, location of air intakes, etc.). Given this, indoor air pollution is highly spatially and temporally variable. For example, one of the key drivers of indoor air pollution is human movements causing the resuspension of settled dust, making it so that classroom air quality is worst when students enter/exit classes for recess or lunch. Researchers in London found that air quality inside classrooms was worse than the air quality outside. Given that students spend one-half of their waking time on weekdays at school, such evidence spotlights schools as a natural location to reduce students’ exposure to air pollution.

In that vein, one way to improve air quality inside classrooms is to upgrade aging schools. Research in this area has been promising, with one study in Texas looking at mold and ventilation remediation projects and finding that these renovations substantially raised test scores by about 0.1-0.15 of a standard deviation. These projects were costly, however, with the average remediation project costing between $300,000 and $500,000. Similar beneficial effects on test scores have been found using new school construction , although these entail even higher costs.

Similar gains can potentially be achieved in a more cost-effective manner. If improved indoor air quality is the driving force behind the large test-score effects of renovated and new schools, then policymakers can target air quality directly. A candidate to do so is plug-in air filters, which are relatively cheap (around $700 per unit) and which have been found to reduce airborne pollutants in classrooms by about 90% . These filters can even reduce virus-containing aerosol particles, with obvious implications for classroom safety in our current pandemic.

On this theme, a unique situation arose whereby air filters were installed in some classrooms in Los Angeles. Specifically, the Southern California Gas Company experienced a large leak at their Aliso Canyon gas storage facility in October 2015 that lasted until February 2016. Understandably, the gas leak generated substantial concerns in nearby neighborhoods, prompting the gas company to pay for voluntary evacuation expenses along with home improvements for those that stayed, including installing air filters and weatherizing homes. The gas company also provided 1,756 plug-in air filters to schools within five miles of the leak.

I investigated the effect of these air filters by comparing schools that received the air filters to nearby schools that did not. I found that schools receiving air filters experienced large test score gains of 0.1-0.2 of a standard deviation that year, particularly in mathematics. These test score gains were similar in magnitude to those from the renovation and school construction studies, but were achieved at a fraction of the cost. While the study relies on a relatively small sample of 11 schools that received the air filters (in comparison to 17 nearby schools that did not), it reinforces the prior evidence that improving air quality inside schools helps students succeed.

The Future of Clean Air in Classrooms

We now have compelling evidence that air quality affects student learning. Low-cost interventions such as air filters may be able to deliver the promised health and academic benefits of cleaner air in classrooms, although more research is needed. More evidence will doubtless follow: For example, the Clean Air, Sharp Minds Act introduced by Sen. Cory Booker (D-N.J.) and Rep. Katherine Clark (D-Mass.) aims to provide $20 million in grants for schools to purchase, install, and maintain commercial air filters and for their impact on learning to be assessed.

While we wait for further evidence, common-sense actions can be taken to reduce the impact of pollution on students. For starters, school officials should avoid locating new schools near highways: California, for instance, banned the construction of schools within 500 feet of freeways in 2003. For the nearly 8,000 existing schools within 500 feet of heavily trafficked roads, officials should test classrooms’ air quality and provide air filters in cases where air quality is poor. Such actions can improve student health and academic performance and, given that economically disadvantaged students disproportionately attend schools in highly polluted regions, help reduce pervasive test-score gaps in public education.

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Introduction to Air Quality

Engage  students with images of air pollution..

• Show images of air pollution around the world in the  SMOG: What it looks like and where it comes from  slideshow. Have students consider the colors they see in the sky and where the air pollution is visible in each scene.  The second half of the presentation includes images of sources of air pollution. Before showing the slides, assess student knowledge about what air pollution is, what it looks like, and pollution sources.

Explore  the sources of air pollution.

• Whirling Swirling Air Pollution : In this activity, students read a story of a typical day in the life of Edgar, a fictional character, and create a simple model that shows the air pollution that Edgar adds to the atmosphere over a 24-hour period.
• Air Pollution Model : Use this model to explore the connections between pollution sources, weather, geography, and air quality. Discover which weather condition causes the development of secondary air pollutants, such as ozone. Compare the effects of two different pollution sources, pollution-control devices, and changing weather conditions on the air quality over a city.

Explain  how air pollutants form using molecule models.

• Modeling Smog : Students are introduced to the chemistry of air pollutants using simple models which show how ozone is made at ground level in the presence of sunlight.

Elaborate  on how types of air pollution impact health.

• Name That Air Pollutant : In this guessing game, students describe and identify four major air pollutants and the effects of each on human health. Student understanding of these major pollutants is built through a reading that describes how human activities contribute to air pollution.

Evaluate  student understanding of the sources and impacts of air pollution.

• Have students make a list of what could be done to reduce the amount of air pollution, and what could be done to reduce the impacts of air pollution on human health. (Student answers should include reducing the sources of air pollution such as auto emissions and factory emissions. Student answers should also address strategies for reducing the impact on human health such as staying indoors at times of day when air quality is low.)
• Then lead a class discussion in which students share their ideas. Consider which ideas are easy to implement and which would take more effort. Consider which are actions that individuals can take, and which would require communities to act together.

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Environmental Issues: Air-Pollution Case Study

Introduction.

One of the most heated debates of the modern era revolves around environmental issues and how best to repair current damages and prevent future damage. Unfortunately this is something of a controversial topic because there are some that heavily support the environment and the protection of it and there are others that actually do not believe that environmental issues are serious at all. That being said addressing a problem that some people will not admit exists is incredibly difficult. This is the case with the modern issues with air pollution.

DISUCUSSION

Atmospheric pollution. case study example, introduction..

Atmospheric pollution can be described as the process to which chemicals, biological material or particulate matter, that are harmful to humans and other living organisms, are introduced into the atmosphere (Jacobson, 2002). Man is considered as the prime polluter of the earth’s atmosphere from his daily activities that involve release of hazardous gas into the atmosphere (Cheremisinoff, 2002). The Environmental Protection Agency (EPA) considers the following six pollutants as principle contributors to atmospheric pollution: Carbon Monoxide, Lead, Sulfur Oxides, Ozone, Nitrogen Dioxide, and Particulate Matter like Sulfates, Nitrates and carbon based molecules (Vallero, 2008).

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ISSUES FACED BY HONG KONG DISNEYLAND ARE AS FOLLOWS:

Sample case study on environmental impacts ground transportation infrastructure development.

Ground transport forms the central nervous system of any economy. It facilitates transport of goods that drives an economy, while also facilitating transport of people. The purpose of transport can be either commercial, business, or for pleasure.

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This paper is going to present a discussion on Nike’s main officers, their compensations and some corporate governance issues that the company is facing.

Nike’s Main Officers

The main officers in Nike include Philip Knight, the chairperson of the Board of Directors; Mark Parker, the President, CEO, and a member of the Executive Committee; Donald Blair, the Executive Vice President and also the Chief Financial Officer; Trevor Edwards, President of Nike Inc. Brand; Jeanne Jackson, President, product and Merchandising; Erick Sprunk, the Chief Operating Officer (Nike Inc., 2014).

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Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc., 467 U.S. 837 (1984)

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The insurance agent was correct that the seafood was contaminated with the fumes that resulted from the fire. Toxic fumes quickly diffuse through the air. The toxic fumes were absorbed by the polyethylene curtain which covered the food despite it being thick (Brook et al. 2660). Therefore, the seafood needed to be thrown away since it had the toxic fumes.

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Air Pollution and Student Performance in the U.S.

We combine satellite-based pollution data and test scores from over 10,000 U.S. school districts to estimate the relationship between air pollution and test scores. To deal with potential endogeneity we instrument for air quality using (i) year-to-year coal production variation and (ii) a shift-share instrument that interacts fuel shares used for nearby power production with national growth rates. We find that each one-unit increase in particulate pollution reduces test scores by 0.02 standard deviations. Our findings indicate that declines in particulate pollution exposure raised test scores and reduced the black-white test score gap by 0.06 and 0.01 standard deviations, respectively.

We would like to thank Claudia Persico and Robert McMillan along with seminar participants at the 11th European meeting of the Urban Economics Association for helpful comments. The views expressed herein are those of the authors and do not necessarily reflect the views of the National Bureau of Economic Research.

MARC RIS BibTeΧ

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An empirical study towards air pollution control in Agra, India: a case study

• Published: 27 November 2020
• Volume 2 , article number  2090 , ( 2020 )

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• Ranjit Kumar   ORCID: orcid.org/0000-0002-8858-7453 1 ,
• Pratima Gupta 1 &
• Ashok Jangid 2  

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Air pollution affects many people in developed and developing countries worldwide. It is costing around 2% and 5% of GDP (gross domestic product) in developed and developing countries, respectively. The air qualities have been deteriorating day by day and now the situation has become worst. An increase in air pollution will worsen the environment and human health status. Hence, there is an urgent need for air pollution control. Air pollution can be controlled by reducing the emission of air pollutants from industrial and domestic sources through source emission control decrease in fuel combustion, modifying technology, and growing plants. This is the ripe time to take some bold steps in controlling the menace of air pollution. The scientific bodies, NGOs, researchers, and policymakers have made several efforts but pollution levels are increasing everywhere. The UNEP (The United Nations Environment Program), IPCC (The Intergovernmental Panel on Climate Change), etc., have prepared several reports and organize every year COPs (Conference of Parties) meeting but all have gone in vain as the main culprit feedback has not been taken into the consideration. So, a sincere effort is required to fight the effects of climate change. This paper presents a case study of the Agra region over the Indo-Gangetic basin. The air quality of different sites in Agra has been evaluated, and a survey has been conducted to get the public opinion on air pollution, causes, impacts, and solutions. 75% of respondents were aware of the poor air quality of Agra, however, the percentage of respondent who was unaware is not small. It is a matter of concern. 85% of respondents think that poor education and unawareness are the major cause of air pollution. They suggested education, value-based education to improve air quality. Based on these outcomes, it has been concluded that nature-based solutions for air pollution control can be achieved by making people environmentally conscious through value-based education.

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1 Introduction

Air pollution, global warming, and climate change have become a big issue all over the world as it affects the entire ecosystem and human health. Air pollution causes climate crisis and biodiversity crises and posed threats to the survival of human beings [ 1 , 2 , 3 ]. It is mainly due to an increase in emissions of polluting gases and particles in the atmosphere. Gases and particles get emitted in the atmosphere from natural and anthropogenic activities viz. residential cooking, vehicles, industries, construction, and deforestation [ 4 , 5 , 6 , 7 ]. About half of the urban population being monitored is exposed to air pollution that is at least 2.5 times higher than the levels with WHO air quality guidelines. Worldwide, the most widely monitored air pollutants are PM, NO 2 , SO 2 , CO, and O 3 . They are also called criteria pollutants as they are the most common indicators of air quality. In India, CPCB (Central Pollution Control Board) classifies cities as critically polluted if the levels of criteria pollutants are more than 1.5 times the standards. New Delhi, Beijing, Agra, Shanghai, and Mumbai are the most polluted cities in the world [ 7 , 8 ]. The PM 2.5 levels of these cities have risen exponentially. It has also crossed the National and International standards (World Health Organization, US Environmental Protection Agency (USEPA), European Protection Air Quality (EUPAQ), China, National Ambient Air Quality Standards (NAAQS), India) (Fig.  1 ).

Source : WHO 2018

The level of PM 2.5 over 20 most polluted cities in the world (standard value of WHO (10 µg m −3 ); USEPA (12 µg m −3 ); EUPAQ (15 µg m −3 ); China (35 µg m −3 ); India (40 µg m −3 )).

Various governmental organizations and international bodies have proved that air pollution is a major risk to the environment, quality of life, and health of the population [ 9 ]. Every year, approximately 6.5 million people die prematurely from illness caused by outdoor air pollution worldwide and premature deaths will rise 90% by 2040 in developing countries [ 7 ]. In the past decades, a considerable magnitude of air pollution pulls up the number of people suffering from respiratory disease and many times leading to deaths or serious health hazards [ 8 , 9 ]. Air quality standards are set by most countries to protect the public health of their citizens [ 10 , 11 , 12 ]. In 2018, the WHO (World Health Organization) compiled a list of top 500 cities by PM 2.5 annual mean concentration across the world. Kanpur had the worst air quality in the world in that list, surprisingly nine other cities of India figured among the top 20 cities of the world viz. Faridabad, Gaya, Varanasi, Patna, Delhi, Lucknow, Agra, Gurgaon, and Muzaffarpur (Fig.  1 ). As per WHO global ambient air quality update 2018, only 3% of cities in low- and middle-income countries with more than 100,000 inhabitants and 51% in high-income countries out of 4300 cities of 108 countries included in the WHO database complies with WHO air quality guidelines [ 8 ].

The air pollution problem was formally recognized in the 1972 United Nations Declaration on the Human Environment and The United Nations Framework Convention on Climate Change (UNFCCC) Conference (COP) 2011, held in Durban, South Africa. COP 2011 had representatives from 194 countries coming together with their progress plans, to finance environment-saving effort through Green Climate Fund. These types of concrete efforts need to be taken continuously and frequently as no single effort can be a panacea to this old sore. A problem of this scale, where causes and its effects are much diverse, it becomes very important to start once again from the basics and basics lies in education and awareness [ 13 , 14 ]. Various studies have been focused on the risk assessment, perception of social factors, awareness among people about air pollution [ 15 , 16 , 17 , 18 , 19 , 20 ]. Improving awareness about sustainability involves issues like the impact of anthropogenic activities on human health, earth system, control of greenhouse gases, energy consumption patterns, pollution, and transport [ 21 ]. Living sustainability depends on a duty to seek harmony with other people and with nature. Recently, in the year 2015, UNFCCC (United Nations Climate Change Framework Convention), COP 21 was held in Paris, where several countries globally debated and came to a conclusion to set a limit of average global temperature increase to 1.5 °C. It directs countries to cut their carbon emission excessively. It can be materialized if people are directly involved in this step along with the industries. The aim of holding the increase in global average temperature below 2 ˚C or 1.5 ˚C would be a herculean task to achieve with current trends of trajectories of global greenhouse gas emissions. The existing trends are only pointing towards more deteriorating conditions as the emission graph is continuously tracked its known trend [ 21 , 22 , 23 , 24 , 25 ]. Postponement of implementation of much-needed changes will only hamper the revival chances through mitigation measures. It is very important to assess, re-plan, re-strategies, and re-prioritize our needs and paths to achieve development keeping the climatic conditions in the loop [ 26 , 27 , 28 ]. In this context, public opinion may be very important and eye-opening. In India, Agra is one of the most polluted cities and at the same time, it is a world-famous tourist destination. Hence, a survey-based study was conducted over the Agra region in India to get a glimpse of thought perceptions of the common public towards regional and global problems like air pollution, its causes, impacts, and solutions.

2 Material and methods

2.1 site characteristics.

Agra, situated at 27.17° N, 78.01° E over the Indo-Gangetic basin is presently among the most polluted cities in the country. The population of Agra is 15,85,704 as per the census of 2011 and the 30th most populated district in Uttar Pradesh in India. The urban agglomeration of Agra has a population of 1,760,285. Males constitute 53% of the population and females 47%. Agra is famous worldwide as it hosts the ‘Taj Mahal’, which is one of the seven wonders of the world, and other historical monuments. The poorly maintained roads, traffic congestion, wood and cow dung cakes burning for cooking, coal, petrol, and diesel combustion, and vehicular emissions in Agra have resulted in the city having a high pollution level. Agra is one of the most polluted cities in India. Therefore, it was an apt choice to do such type of study.

In this study, the data have been collected in the form of a survey. A questionnaire was developed (Fig.  2 ), served to the local community, and information was collected from various departments, colleges, and schools of Agra as well as local people. The response can be a real representation of the opinion of the common people towards such global challenges of air pollution. This also enables us to develop an understanding regarding people’s limited knowledge about environmental issues and shortcomings of the existing education system. The survey reported the educational approaches used in air quality research communities, both nationally and internationally. There are many factors which make an impact on individuals and community related to environmental concern, and there are various ways that people can learn about environmental issues and how to address them. Out of the total persons who took part in the survey, 20% of the respondents were females and 80% were male (Fig.  3 ). 50% were living in urban areas, 40% were from rural areas, whereas 10% were from suburban areas. 6% of the survey takers were in the age group of above 40 years, 56% were in the age group of 10–20 years, whereas 38% were in the age group of 21–40 years. The questionnaire survey has been designed in a very simple manner which is easily understandable for the local community in Agra. The questionnaire of survey data was collected by the researcher by offline mode. Before the statistical analysis, screening of survey data has been done and the responses were cross-checked.

Questionnaire of survey

Percentages of the respondent a area, b gender and c age ratio

2.3 Statistical analysis

Statistical analysis was employed on the datasets using SPSS. The nonparametric method was used for the determination of the statistical significance of the collected survey data. The t test has been used to assess the relationship between two categories of variables amongst gender, area, and age. The significant level was set at p  < 0.05.

3 Result and discussion

3.1 key findings of the survey.

The feedback based on the survey conducted in Agra is very much fact-finding and presented in Figs.  4 and 5 . There were 20 questions which have been asked to the respondent in the questionnaire regarding various issues related to air pollution, and their response statistics were plotted. The feedback of the respondent has been categorized into three major categories; gender, area, and age-wise. The views on the ways societies come to know about air pollution problems may reveal values, beliefs, and varieties of “truths” underpinning how problems are identified and approached. 91% of the total respondents (72% male and 19% female) (Figs.  4 (1) and 5 (1)) believe that air quality has deteriorated in the last few years. In (Figs.  4 (2) and 5 (2)), 95% of total respondents in which 75% male and 20% female accepted that air pollution harms humanity. Air pollution is a serious problem, 75% of the total respondents (65% male and 10% female) know and understand the extent to which it can damage their life but 22% of respondents were in the opinion that air pollution will affect little while 3% are ignorant, which is a very large number (Figs.  4 (3) and 5 (3)). This is worrisome. They know the health hazards of air pollution and 73% of respondents blame air pollution for irritation in the eyes, nose, and throat, breathlessness is marked by 22%, and 5% think that depression may be also due to air pollution (Figs.  4 (4) and 5 (4)). 45% of the total respondents (35% male and 10% female) stated that the pollution level in Agra is cleaner than other big cities and the other 55% say it is worse (Figs.  4 (5) and 5 (5)). Cooking fuel is found to be one of the major causes of air pollution as 93% of respondents were dependent on LPG (liquefied petroleum gas) as a mode of cooking while the rest of the respondent relies on kerosene, coal, and wood (Figs.  4 (6) and 5 (6)). People were in a clear opinion that polluting companies should be fined heavily to cut down air pollution even it may put some jobs at risk. They believe that citizens should now take the initiative in their hands for clean air and a safe environment and ask authorities to take actions judiciously. 92% of the total respondents (73% male and 19% male) were of the view that the ultimate solution to this glaring situation of global warming and climate change can be tackled by making common masses aware of causes, consequences, and culprits of air pollution (Figs.  4 (8) and 5 (8)). Environmental education may be an important means and 95% of respondents in which 84% male and 11% female feel it may improve public understanding of environmental issues (Figs.  4 (9) and 5 (9)). 91% respondents know the air quality index (AQI) (Figs.  4 (10) and 5 (10)). The excess use of energy causes air pollution, 84% of the total respondents (66% male and 18% female) are aware that air pollution is due to excessive use of energy, while 16%, which is not a small number, are unaware (Figs.  4 (11) and 5 (11)). The biggest source of knowledge regarding the air pollution and environment is print media, although digital media have surpassed all records of visual advertisement as 73% say newspapers are their main source on environmental issues whereas only 26% say it is a television (Figs.  4 (12) and 5 (12)). In the response to the question of the moral responsibility to minimize air pollution, 98% of the total respondents (81% male and 17% female) feel that air pollution control is our moral responsibility and believe that the negligence of our moral responsibility is doing more harm to the environment than any other thing (Figs.  4 (13) and 5 (13)). 98% of respondents in which 82% male and 14% female were in view that bringing certain changes in daily habits of life may minimize the energy consumption (Figs.  4 (14) and 5 (14)). But the positives that can be taken from this survey is that they are ready to make changes in their lifestyles and want to contribute to the fight against the menace of air pollution. Taking moral responsibility is important to overcome this problem as 91% of the respondents (73% male and 18% female) feel that it is the selfish interest of some people that are hampering the cause (Figs.  4 (15) and 5 (15)). 98% of respondents in which 82% male and 16% female stated that ignorance of moral responsibility for self-interest or may be due to unconsciousness towards the human values (Figs.  4 (16) and 5 (16)) may be proven to be dangerous. Various studies have suggested that interest, beliefs, values, and the basis of knowledge power are linked with culture, nature, and economy [ 11 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. 98% of respondents have shown their willingness to take some steps for clean air and bring some changes in attitude regarding environmental issues. 95% believe consciousness and human values will go a long way (Figs.  4 (17) and 5 (17)). The socio-ecological approaches to environmental education emerged as ways for dealing with conflicting multilayered demands concerning the environment. The research finding of this survey was very similar to the earlier studies for socio-ecological perspectives on environmental education [ 11 , 12 , 20 ]. The characteristics of the survey were outlined for providing the foundation of socio-ecological approaches. The socio-ecological approaches illustrate how environmental problems are addressed, inquired, analysed, interpreted, and what conclusions are drawn regarding the solution of air pollution [ 36 ]. 98% of respondents in which 78% male and 18% female are of the view that student life is the time to lay the foundation of intellectual and conscious citizens (Figs.  4 (18) and 5 (18)). 96% of them in one voice say that value-based education from elementary level can inculcate the habit of energy efficiency as well as consciousness towards the environment. They also believe that this will produce future intellectuals and very informed citizens (Figs.  4 (19) and 5 (19)). 97% of people in which 80% male and 17% female say that value-based education should be added to the curriculum starting from elementary level to research courses because our existence can only be supplemented on the pillars laid by the educating system (Figs.  4 (20) and 5 (20)). The statistical analysis was performed on the dataset, and the t test for all variables has been found statistically non-significant at p  < 0.05. The t test with the participants from different gender, age group, area-wise, and questionnaire is presented in Table 1 . The categories of gender, area, and age have been observed that the p value ( T  <  =  t ) was less than the absolute value (critical value). Respondent was positively found to be statistically significant with gender especially in males ( p  = 0.28). It may be due to the fact that the male respondent is more exposed outdoor than female ( p  = 4.0 × 10 –7 ). In the area-wise, the respondent from a rural area ( p  = 0.036) has shown the statistical significance than urban ( p  = 4.3 × 10 –6 ) and suburban (1.4 × 10 –8 ) area. The p value of different age group viz. below 20 years, 21–40 years, and above 40 years was less than the absolute value. The age group below 20 years ( p  = 0.01) was positively significant than other age groups. It may be due to the fact that the youngster is more sensitive to air pollution than older. Therefore, the results of the age group of 21–40 and above 40 years were not statistically significant.

A statistical response of total respondent to questions of the survey

Response to the questions of questionnaire

In the study, it is quite evident that the participation of females is limited. It may be due to their illiteracy and socio-economic status and understanding of air pollution and other environmental issues. There is an urgent need to enhance their understanding of such a common public problem of air pollution. The government should come up with a different innovative scheme and value-based education to address these issues. Value-based education means to be a starting point of the real-life solution where people are directly involved. They also expressed their fear in the feedback remark that they are sitting on a pile of explosives and in a situation of now or never. It will be too late if some drastic steps are not taken immediately. But it is also a fact that this survey was conducted in educational institutions and nearby areas where people are more active and are educated. But still, many are unaware of several implications, causes, and remedy of the menace of air pollution. So, a condition in core civil areas may be more disturbing.

3.2 Perception of value-based education

Education is an act of acquiring or imparting a particular set of knowledge or skills through the process of learning or teaching, especially in schools or colleges. But the most important demand for time is to change and that change should also be reflected in the education system. The necessity to add values of education has risen. The addition of values does not kill the essence of the traditional educational methodology but complements it. Value-based education integrates ethics, moral duties, cultural importance which develops the trainer as well as the learner to be a better human being. It is just a way of conceptualizing existing education practices with the purpose of good for all, at the core of its heart. It initiates a positive relationship with everything living or non-living around. It teaches to give respect to others whether living or non-living. The changes happening around the world are badly affecting the environment and there is a need for value-based education to educate people and come up with new ideas/techniques. These scenarios can be coupled with various areas, i.e. value-based education, socio-economic, climatic, cultural, and behavioural impact. The perspective needs to be discussed and a plan needs to be unraveled that how to implement these scenarios step by step to provide a complete framework of implementing value-based education in true spirit. Environmental problems need to be addressed through value-based education as it provides an opportunity to educate and train the people who are or will be making or breaking the environment further. This type of education should start from the elementary level to the advanced level and then to a very advanced level. The crucial and most difficult step of the method is the implementation of plans as it demands changes in the way of life morally and the integrity of the administration to implement. Many times it demands changes in existing laws into a more stringent one, despite drawing flak from some parts of the society.

3.3 Control of air pollution: value-based education

Air pollution can be controlled through nature-based or technology-based solutions. Technology-based solutions control one type of pollution but also add other kinds of pollutants to our environment. The outcome or findings of the present survey provoked the nature-based solution of air pollution, global warming, and climate change. The result of the survey conducted clearly shows that people have migrated from sustainable development to unsustainable development mainly due to their ignorance towards the environment and selfishness. People accept their negligence and unawareness. The survey also points out that people due to their selfish ends sometimes do not care about the environment. The survey also had a suggestion-based question in which it was asked to suggest ways to control the menace of air pollution. Respondents suggested that environmental education be imparted from the elementary level and organizations such as educational institutions, the social, or religious body should be a frontrunner to bring changes in habit of inhabitants. They also suggested that the government should frame stricter laws and ensure its implementation. Reduction in the use of private vehicles and control in the consumption of energy were pointed out. A lot of people came out with the idea of the extensive plantation. Almost everyone suggested practical awareness among citizens in the form of workshops/conferences/seminars on causes, impacts, and solutions to air pollution. The new generations with the proper guidance of experienced are ready to embark on the journey to integrate value in the education system and also to work together for sustainable development. People are ready to improve their understanding of society and the common public on climate and future socio-economic scenarios. These deeply rooted values can be imbibed in students through value-based education. Some steps to make them aware have already been taken, but a lot needs to be done.

Based on the response of respondents, four-step strategies have been proposed viz. measurement and assessment, set standards, reduction of emission, and implementation (Fig.  5 ) to combat the menace of air pollution. Measurement and assessment of air quality are required and it involves the general public, local communities, schools, university, industry, non-governmental organization, community groups, and NGOs. There is a need to set the standard through consensus amongst stakeholders, policymaker/decision-makers, industrialists, media, and the common public. There should be separate emissions standards for different sources. The reduction of emission at the source can be achieved by the betterment of technology through modification and replacement of existing equipment with more advanced ones. Hence, the reduction in dependencies on fossil fuels and the identification and use of clean and alternate energy sources are needed. Implementation and execution are of the most important as the whole model relies on the success of these steps. Hence, the direct involvement of the government body and judiciary is required. These four-way efforts should be made in parallel. This is like 1-2-3-4 formulae to formulate the problems of air pollution. Individuals (adults and children) may change their behaviour when their values, beliefs, and environmental understanding improve which can be achieved by becoming conscious of the environment. The new process of bidirectional perception is only a step towards bringing the separate tasks under one single umbrella (Fig.  6 ). There should be effective in dealing with the exchange of information, data collection, knowledge, interpretation, implementation, and further actions and co-ordination between organizations. Value-based education will be the central idea of the bidirectional perception process, as it will develop a sense of working together in teams, bringing about a change in the thinking of present and generations to come. All this will go to improve the knowledge of air pollution, climate change, and mitigation. The contribution of the common public is the only way of success. But to develop a sense of belongingness with the environment, they must know about air pollution and its vulnerabilities. It should be backed by the proper amalgamation of scientific advancements and inculcation values and ethics in an individual which can be achieved through value-based education and being environmentally conscious. Its implementation should be time-bound and impacts must be monitored. Any control technologies can never be full-proof for such a diverse and complex issue of air pollution and climate change, but when efforts are made honestly and implemented properly, surprising results come. This mechanism may be very effective, cost–benefit, and sustainable.

Bidirectional perception of the process of value-based education

3.4 Policy implications

The findings of this survey suggested the awareness of air pollution and the implementation of air quality control measures. Value-based education can be a powerful tool to make people aware of such relations and get rid of ignorance. Therefore, value-based education has to play an important role. It builds character which is beneficial for the growth of both the individual and the societies. Value-based education also seeks to integrate the principle, values, and practices of sustainable development into all aspects of life, to address the social, cultural, and environmental problems we face in the twenty-first century. Environmental literacy for adults means developing and participating in social practices likely to change the way our societies think about and act upon ecological issues. Nature-based solutions and sustainable consumption and production is the need time and needed to be included in government policies.

3.5 Limitations of the work and potential future work

The present study focused on the public perception of the status of air quality in the Agra region over north-central India. Air pollution has become a big issue nowadays all over the world. The main sufferer of air pollution is human being and the main culprit is also human beings while the main cause of air pollution is indiscriminate exploitation of natural resources and excessive consumption of energy by human being. All the efforts made so far to control air pollution were technology-based in spite of knowing the fact that human being is the main culprit. In this study, the common public has been involved and opinions were invited in the form of questionnaires regarding causes, impacts, and solutions of air pollution. Respondents feedback were torch-bearing for environmentalists, educationists, academicians, government body, and stakeholders for the plan. Input obtained from the respondents of the Agra region only but it can be considered as a pilot work and can be representative of a regional perception on such a global problem. This is a limitation of this work. In the future, such type of a comprehensive study is required by involving the public of all segments which may help to design a proper plan for pollution reduction and a healthy environment.

4 Conclusion

A survey-based on questionnaires has been conducted to know the views of the public and explore the role of education in control of air pollution over the Agra region in north-central India. This study reveals that the public is aware of deteriorating air quality, but they are not making efforts to fight them just due to ignorance and their selfishness. Based on the feedback of respondents, following conclusions and suggestions have been derived:

A change in habit and lifestyle is required.

Ban on the industry which pollutes air even at the cost of employment is needed.

Value-based education is needed to combat the menace of air pollution.

The ultimate solution to the air pollution problem is making the people aware of the causes, consequences, culprits, and control of energy consumption through education.

A four-step non-destructive and holistic method has been suggested for air pollution control which can be achieved through value-based education and being environmentally conscious.

Nature-based methods should be adopted for control of pollution as technology-based solutions are specific.

An organization like educational institutions, indigenous groups, and religious bodies should be involved as they will act as a catalyst for bringing change in habit of the common public and future generation.

Data availability

All the generated and analyzed data are included in this article.

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Acknowledgements

We wish to thank all the participants of the survey for their voluntarily support. We wish to thank Prof. Sahab Dass, Head, Department of Chemistry for providing necessary facilities and kind encouragement. The help and support from Mr. Hazur Saran is greatly appreciated.

The financial assistance from ISRO-GBP project is gratefully acknowledged.

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R.K. has planned the work and designed the manuscript. P.G. has done experimental works and wrote the paper. A.J. has made figures. R.K. has planned the work and designed the manuscript. All three authors have reviewed the paper a number of times.

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Kumar, R., Gupta, P. & Jangid, A. An empirical study towards air pollution control in Agra, India: a case study. SN Appl. Sci. 2 , 2090 (2020). https://doi.org/10.1007/s42452-020-03826-4

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Received : 31 March 2020

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Published : 27 November 2020

DOI : https://doi.org/10.1007/s42452-020-03826-4

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Exposure to air pollution and self-reported effects on Chinese students: A case study of 13 megacities

Sohail ahmed rajper.

School of Life Sciences, Nanjing University, Nanjing, Jiangsu, P.R. China

Zhongqiu Li

Associated data.

All relevant data are within the paper and its Supporting Information files.

Air pollution causes severe physical and psychological health complications. Considering China’s continuously-deteriorating air quality, this study aimed to assess the self-reported effects of air pollution on the behavior and physical health of the students of 13 densely populated cities, and their awareness, practices, and perception of air pollution and its associated public health risks. A detailed, closed-ended questionnaire was administered to 2100 students from 54 universities and schools across China. The questionnaire, which had 24 questions, was categorized into four sections. The first two sections were focused on air pollution-associated behavior and psychology, and physical effects; while the final two sections focused on the subjects’ awareness and perceptions, and practices and concerns about air pollution. The respondents reported that long-term exposure to air pollution had significantly affected their psychology and behavior, as well as their physical health. The respondents were aware of the different adverse impacts of air pollution (respiratory infections, allergies, and cardiovascular problems), and hence had adopted different preventive measures, such as the use of respiratory masks and glasses or goggles, regularly drinking water, and consuming rich foods. It was concluded that air pollution and haze had negative physical and psychological effects on the respondents, which led to severe changes in behavior. Proper management, future planning, and implementing strict environmental laws are suggested before this problem worsens and becomes life-threatening.

Introduction

Air pollution is of serious concern across the globe, and is fueled by rapid population growth, continuous urbanization, increases in industrialization, continuous rises in energy demand, deforestation, and increases in car density, especially in major cities [ 1 , 2 ]. Various anthropogenic activities lead to atmospheric degradation, such as emissions from vehicles, especially those that are older or poorly maintained; coal-powered industrial activities; construction, which produces dust; foundries and smelters; tobacco use; combustion that produces enormous heat; metal-based industries; mining; and excessive pesticide and chemical use [ 3 – 7 ]. This bleak scenario is further worsened through poor environmental management and regulation, use of inefficient technologies (with low production and high environmental deterioration), construction of congested roads, and the inability to strictly implement environmental regulations and laws, as well as a lack of awareness among the population about the serious health and psychological outcomes of pollution. This issue is even more prominent in underdeveloped and developing countries, where it is a serious concern as it adversely affects public health, alters the quality of life, and impacts the economy (by affecting agricultural production, for example) [ 8 , 9 ].

Atmospheric heavy metals (lead, mercury, copper, zinc, cobalt, nickel, and cadmium), SO 2 , CO, NO 2 , benzene, particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), and chlorofluorocarbons (CFCs), are the primary contributors to air pollution [ 7 , 10 – 12 ]. The presence of these pollutants at levels beyond permissible limits causes serious health issues, such as breathing problems, allergies, cancers, cardiovascular and respiratory diseases, and even mortality [ 12 , 13 ]. Elders, infants, toddlers, children, sensitive people, and those suffering from asthma and such other disorders are more vulnerable (physically and psychologically) to the effects of air pollution [ 14 , 15 ]. Higher temperatures and air pollution are also associated with low mood and potency [ 16 , 17 ], changes in sexual behavior, and negative effects on reproductive health [ 17 , 18 ]. The World Bank [ 19 ] has provided an excellent updated insight of the fertility rate for all countries around the world, based on total births per woman, which could be linked to global warming/greenhouse gases and air pollution [ 17 , 20 , 21 ]. Kihal-Talantikite et al. [ 22 ] extensively reviewed the adverse impacts of proximity to polluted areas on the outcomes of pregnancy, such as infant mortality, premature birth, low birth weight, congenital malformation, intrauterine growth retardation, and gestational age. The physical effects associated with air pollution are widely studied, reported, and reviewed [ 23 – 28 ].

Numerous studies have demonstrated a positive correlation between air pollution and mortality across the globe, including in China [ 12 , 29 – 32 ]. Researchers have reported that 3–7 million deaths over the past few decades were caused by cardiovascular diseases (CVDs) after continuous exposure to excessive levels of airborne PM [ 33 – 36 ]. Industrial power plants, vehicle emissions, fossil fuels, and biomass combustion have been identified as major sources of PM, which acts as a primary pollutant and a secondary product of different gases, including NH 3 , NO x , and SO 2 [ 12 , 27 , 34 , 35 ]. Time-series studies have assessed the association between daily mortality and ambient air pollution in different western countries [ 29 , 37 – 39 ], and different major Chinese cities, including Hong Kong [ 40 ], Wuhan [ 31 ], Guangzhou [ 41 ], Shanghai [ 30 ], and Beijing [ 27 ].

Approximately 800 million people were affected by the hazardous dense haze (covering an area of 1.4 million km 2 ) in January 2013, which generated serious concern about air pollution among the residents of Eastern China [ 15 , 42 ]. Yang et al. [ 32 ] reported that 1.2–2 million deaths per annum in China are attributed to air pollution, which was the fourth most prominent cause of disability-adjusted lifespans. Lu et al. [ 43 ] reported that rapid industrial, urbanization, and population growth are major sources of China’s continuously-deteriorating air quality, and are posing a significant threat to public health. Approximately 65–75% of industrial powerhouses in China are still coal-operated (i.e., coal is a major fuel source), and are designated as major pollution sources [ 6 , 44 ]. Owing to the current situation, air reporting systems have been developed and installed in 190 cities (945 sites) across China. This system reports air quality on an hourly basis, focusing on six air pollutants: PM 2.5 (PM<2.5 μm), PM 10 (PM<10 μm), SO 2 , NO 2 , O 3 , and CO. Estimating and understanding outdoor air pollutants and their burden on public health would help to control air pollution [ 13 , 43 ].

Air pollution is one of the leading factors that upsets human emotions and alters behavior [ 45 , 46 ]. Long-term exposure to polluted air results in a variety of psychological problems (such as stress, depression, anxiety, irritation, becoming short-tempered, and mood swings), which adversely affect behavior (such as eating, recreation, commuting, traveling, and socialization) [ 13 , 23 , 47 , 48 ]. A recent study indicated that older people and females were suffered more and were more anxious because of low air quality than younger people and males [ 49 ]. Various studies have demonstrated the positive impacts of clean air on the human psyche, resulting in a pleasant mood and positive behavior [ 50 ]. Similarly, different studies have revealed a positive correlation between increased criminality (aggressive and violent behaviors) in humans and elevated temperatures (specifically in the summer) and air pollution [ 51 – 53 ]. Air pollution has also been correlated with depression, a serious mental disorder affecting people globally, which is continuously increasing [ 54 ]. Depression is characterized by a loss of pleasure and interests, guilt, sadness, inter alia, decrease in libido, disruption to sleep, and a loss of concentration [ 17 ]. There are several studies available that show a positive correlation between air pollution and depressive disorders that adversely affect human behavior [ 55 – 57 ].

Air pollution-associated mortalities [ 27 , 32 ]; and age-, gender-, and season-dependent adverse impacts/effects of air pollution on humans [ 58 – 60 ] are well documented, but most of these studies focused on physical factors. Therefore, an effort was made to study the effects of air pollution on both the physical and psychological health of Chinese students using a detailed questionnaire, and the first two portions were dedicated to each physical and psychological health.

Material and methods

The study was conducted according to the Ethics Review Committee of Nanjing University (No. 2009–116). The Questionnaires were administered to the students following informed verbal consent. All participants were thoroughly informed of the purposes and contents of the project. All participants had the right to answer all or part of the questionnaire, and the right to stop participating at any time-point. They were requested to complete the questionnaires, then and there. Using questionnaire for data/information acquisition, the committee approves informed verbal consent, and hence it was considered to lessen time spent by the students or/and trouble to the students.

In this study, a comprehensive questionnaire ( S1 File ) was distributed to 2100 randomly-selected students from the chosen universities and schools. Questionnaires that shared identical answers to all questions, and those with a large number of missing answers, were excluded from the analysis. After removing these questionnaires, a total of 2048 questionnaires from 13 major cities across China were analyzed, including Beijing (Northern China), Baoding (Northern China), Nanjing (Eastern China), Shanghai (Eastern China), Hangzhou (Eastern China), Xi’An (Northwestern China), Lanzhou (Northwestern China), Harbin (Northeastern China), Shenyang (Northeastern China), Chengdu (Southwestern China), Nanning (Southern China), Changsha (Central China), and Wuhan (Central China). The sampled cities are indicated in Fig 1 .

The questionnaire contained a series of questions to elucidate the individual impacts of haze and air pollution on the physical and psychological (behavioral) health of the subjects. The questionnaire was prepared in two languages, English and Chinese. The questionnaire was split into four sections, two of which were dedicated to the effects of air pollution on behavior (caused by psychological adversity) and physical human health, while the final two assessed the respondents’ knowledge, attitude, and practices (KAP); and sources of knowledge and perception of air pollution and its associated health risks. The survey was conducted over a period of six months, from October 2015 through March 2016. This period was selected because air pollution and haze are often at their highest during these six months.

Haze appears for ≥100 days per year in the Yangtze River Delta, and for ≥200 days in some of the studied Eastern China cities [ 25 , 61 , 62 ]. The surveyed cities were chosen as they are more densely populated (megacities) than other smaller cities. The primary data was obtained through the questionnaire that was administered to students of 54 different universities and schools, which had lived there for over a year, across the sampled locations. The subjects were approached at different points of the universities and schools, including campus areas, playgrounds, laboratories, cafeterias, classrooms, libraries, coffee shops, and waiting rooms, to ensure that individuals with different mood states at that time were included, so that the broader impact of pollution on them could be observed. Similarly, it was ensured that universities and schools situated near roadsides (transportation emissions), in heavily congested and industrialized areas (high levels of combustion, effluent emissions, and fossil fuel use), as well as those in less crowded areas, were included.

The data obtained were imported and analyzed by MS Excel, Origin Pro8.5, and Statistix (Version X) respectively. Based on the previous studies, a Chi-Square (independence) test was conducted to determine the association of gender and age with the responses to all sections of the questionnaire and examine gender- and age-dependent effects, perceptions, attitudes, and practices. Descriptive statistics (frequencies/proportion) were used to summarize the demographics of the respondents, their attitudes, practices, and perceptions to air pollution and its associated health risks, as well as the adverse effects of air pollution on their behavior (psychology) and physical health. A p -value below 0.05 (two-sided) was considered to be statistically significant. To avoid family-wise error, Bonferroni type adjustment (Bonferroni correction) was carried out by adjusting α value (α original ), by defining new α value (α altered = 0.05/number of possible comparisons/analysis for each of the question, shown in Table A in S2 File ). The map presenting the sampled cities was prepared in ArcGIS (V. 9.3).

The study included a total of 2048 subjects, who were recruited from 54 universities and schools across China. The largest number of individuals was recruited from Nanjing (21.2%), followed by Beijing (12.5%) and Changsha (11.2%). It was ensured that participants from different age groups were included. Of the total respondents, 47.3% were 16–25 years old. The study considered both genders; 55.2% of the subjects were female, while 44.8% were male. Table 1 presents the demographics of the respondents that took part in this study. Table 2 shows the average of air quality pollutants for the sampled cities. Table B in S2 File shows the interquartile ranges for the air pollutants across the samples cities (Oct 2015—March 2016).

*Percentage given

Autumn* = October to December 2015; winter** = January to March 2016

The first section of the questionnaire covered the adverse impacts of air pollution on the physical health of the recruited subjects. Of the total respondents, 88.9% reported that they have felt (always, often, and some of the time) the ill effects of air pollution, suggesting that air pollution is a major public health concern across China. The subjects suffered from different effects at varying magnitudes; 25.0% often suffered from sneezing, a dry throat, and eye irritation, and 34.0% occasionally experiences these effects. Of the total respondents, 62.0% had suffered (always, often, and sometimes) breathing problems and have faced respiratory problems. Fewer people suffered from coughing/wheezing and headaches/dizziness than those that have suffered from other ENT (ear, nose, and throat) problems. In total, 9.1%, 10.5%, and 24.6% of the respondents always, often, and sometimes felt that they had lower energy levels in response to air pollution, respectively. For sleeping patterns, 8.7%, 11.5%, and 23.4% of the respondents always, often, and sometimes faced problems in their sleeping patterns, respectively. Table 3 shows the reported physical health effects caused by air pollution, while Tables ​ Tables4 4 and ​ and5 5 contain gender- and city-, and age-dependent responses, respectively.

* = bold value represents p -value < 0.05

a = p -value < α altered (Significant after Bonferroni correction);

b = p -value > α altered (Non-Significant after Bonferroni correction/adjustment)

The next section of the questionnaire was focused on the behavioral and psychological impacts of air pollution. In total, 62.1%, 78.1%, and 65.5% of the respondents suffered from depression/sadness/unpleasant moods, reduced exercise routines/jogging speed/jogging duration, and reduced walking speed, respectively, due to air pollution. A total of 1136 (55.4%) respondents reported that they feel anxiety and frustrated during hazy days. Of the total respondents, 44.1% reported that they become aggressive due to haze/air pollution, and a higher number reported that they exhibit more aggressive behaviors during warmer days (63.9%) than they do during colder days (27.6%). Table 6 shows the behavioral effects of air pollution noted by the respondents, while Tables C and D in S2 File show the reported gender- and city-dependent, and age-dependent effects, respectively.

The third section of the questionnaire contained questions about the preventive measures adopted by the respondents. Of the total respondents, 68.2% reported that they use a mask to cover their noses and mouths, 22.0% used eyeglasses/goggles to protect their eyes, 63.2% drink more water to help them flush out toxins (absorbed through the lungs/skin), and 65.2% indicated that they have a rich diet (high levels of vitamins C and E, and Omega-3-Fatty acids) to improve their immune response. Table 7 shows the practices adopted by the respondents to prevent the adverse impacts of air pollution, while Tables E and F in S2 File show the gender- and city-, and age-dependent practices, respectively.

The final section of the questionnaire evaluated the recruited individuals’ awareness levels and perception of pollution. Of the total subjects, 96.0% reported that smoking should be banned in public areas and restricted to designated zones, 69.3% were aware that air pollution causes cardiovascular diseases and respiratory problems, such as lung cancer, and that air pollution was one of the major causes of mortality in China over the last two decades. Regarding industrialization, 68.8% of the respondents did not agree with compromising their health because of environmental and air pollution originating from China’s development, economic strength, and GDP growth from industrialization. Of the total subjects, 91.9% were aware of major pollutants, such as CO, SO 2 , and NO 2 . Vehicle exhausts (27.8%), industrial emissions (27.8%), and coal burning (21.4%) were identified as major sources of air pollution ( Fig 2 ). Television (20.8%), cell phones (20.6%), and the internet (20.5%) were the leading sources of information about air pollution and its adverse health effects ( Fig 3 ). Table 8 shows the respondents’ levels of awareness and perception of air pollution and its associated health risks, while Tables G and H in S2 File show the gender- and city-, and age- dependent knowledge and perceptions of air pollution, respectively.

China is currently facing prominent and complex issue of air pollution due to a rapid increase in urbanization and economic growth caused by heavy industrialization [ 43 , 63 , 64 ]. Environmental degradation could become more severe if proper management, environmental safety, and planning are not assured by environmental protection agencies, and the current scenario continues [ 11 ]. Over the past two decades, the infrastructure of almost all major Chinese cities has improved considerably, with extensive reconstruction in urban areas and modernization of industries [ 49 ]. In China’s major cities, subway systems are under development, along with other governmental and non-governmental infrastructures. The construction and expansion of these other infrastructures have attracted large numbers of workers from the countryside, elevating the population density of these cities. They have also resulted in an increase in urban air pollution, increasing the vulnerability of residents to adverse health effects [ 11 , 65 ]. The ill-effects of long-term exposure to air pollution on human health, such as weakening/damaging the immune system, respiratory problems, low birth weight, and increased head circumference of children at birth, have been well-document [ 66 – 73 ]. Air pollution can cause mortality if different pollutants are present and exceed their permissible limits, for example, from continuous exposure to air containing 0.001% CO [ 74 ]. According to a report by the World Health Organization, urban air pollution (indoor and outdoor) contributes to over 2 million premature deaths per year [ 75 ]. According to the Global Burden of Disease study [ 26 ], of the 15 countries, China ranked first for premature mortalities (over 1.3 million premature deaths), which were attributed to ambient air pollution, while the preventable death rate was higher for Chinese megacities, including Beijing, Shanghai, Chengdu, and Tianjin [ 76 ].

The aim of this study was to develop a more comprehensive model for the widely prevailing social problem of air pollution, which covered almost the whole of China, but specifically major cities. This study provides better insight for breaching the gap between public health KAP and scientific research than previous studies on this issue, as they were confined to certain places, such as a single city or province. However, our study was conducted in all of China’s major cities. This study strengthens the available literature [ 28 , 49 , 77 ] for all the relevant governing bodies, institutions, and agencies, and acts as a reference for mitigating the current scenario and preventing or reducing future risks and hazards caused by air pollution and its sources. According to Omanga et al. [ 78 ], an awareness of the public’s perception of pollution and its associated health risks is useful for designing and adapting suitable intervention programs.

Several studies have elucidated the impacts of air pollution on the respiratory system [ 68 – 70 ]. Respiratory disorders caused by air pollution include coughing, bronchitis, emphysema, and lung cancer [ 73 ], rendering individuals who are already suffering or have suffered from cardiac failure, chronic obstructive pulmonary disease, and asthma, more vulnerable [ 79 ]. According to Botkin and Keller [ 80 ], those already suffering from respiratory disorders are the most vulnerable to air pollution. In this study, over 98% respondents reported that they have felt adverse physical effects (ranging from experiencing them all the time to rarely) due to air pollution; while only 1.3% responded that they never felt such effects. This signified that the sampled cities currently have poor and polluted air conditions. Other reported physical problems including flu (a runny nose), a dry throat, eye irritation, shortness of breath, reduced lung functioning, coughing/wheezing, headache/dizziness, reduced energy levels, and sleeping disorders. The severity of these problems reported by the respondents was in various ranges. The variation in these responses could be attributed to the health status of the individuals, variations in the pollution levels of the studied cities, and genetic polymorphism [ 81 – 83 ]. The reported results are consistent with those of previous studies, revealing the same adverse health effects from exposure to air pollution [ 34 , 84 , 85 ].

Positive psychological effects, better mental health, and appropriate behavior result from a suitable and clean environment, and comfortable weather conditions [ 50 , 86 – 88 ], while an unhealthy environment has adverse effects on behavior and psychological and mental health, and causes abnormalities [ 55 – 57 , 89 , 90 ]. Polluted air exacerbates stress and depression, and alters behavior [ 14 , 56 , 73 ]. Sahari et al. [ 91 ] reported that poor atmospheric conditions (air and temperature) around living spaces and residential areas was a major cause of stress in humans. According to Brealey [ 92 ], stress is contagious, and is a physical and emotional response to pressure. Shahrom [ 93 ] described stress as a feeling of discomfort in oneself that influences the mind, however, according to Fadzillah-Kamsah, stress covers the following feelings: burden, worry, strain, conflict, pressure, feeling, fatigue, helplessness, panic, and depression [ 94 ]. Sahari et al. [ 94 ] comprehensively reviewed stress, and Łopuszańska and Makara-Studzińska [ 21 ] provided an overview of air pollution-associated depression.

Different stressors that trigger behavioral changes in humans have been explored. Tay and Smith [ 95 ] identified that peoples’ working styles, job nature, recreation methods, lifestyle, and local weather affected their behavior. Turkington [ 96 ] listed financial condition, family problems, social life, home problems, illness, time mismanagement, and job/career problems as primary factors affecting behavior. Shahroom [ 93 ] suggested that spiritual, social, physical, and biophysical factors affect behavior, while the most recent research revealed that environmental conditions (including air pollution and temperature) are primary stressors, as indicated by a number of researchers [ 46 , 55 – 57 , 91 , 94 , 97 – 98 ]. Torres and Casey [ 48 ] identified that mental health, affected by climatic changes or air pollution, is one of the main reasons for migration and disruption of social ties.

Air pollution has an adverse effect on outdoor and sporting activities that are practiced for maintaining an individual’s health and fitness [ 99 ]. In this study, it was reported that 78.1% of the respondents jogged faster and for a shorter duration on hazy days, while 65.5% walked faster in response to air pollution. Air pollution change behaviors associated with sports, such as going outside for games, exercise, and gymnasia. The stamina and physical strength required for partaking in sports are reduced by air pollution, as pollutants such as heavy metals and PM penetrate the lungs deeply and are not easily removed by exhalation, altering the duration and general willingness of people to partake in such activities [ 65 ]. To remove toxic pollutants, 63.2% of the respondents reportedly drank more water on hazy days, compared to normal or pollution-free days. There was no significant difference in water intake between different age categories and genders, which demonstrated that all respondents drank enough water to minimize the risks of air pollution, irrespective of their age and gender. Awareness and knowledge of air pollution might improve this scenario, and could encourage normal sporting behavior and change the attitude of the population towards air pollution-associated adverse human behavior [ 100 ].

Previous studies [ 101 , 102 ] reported that the perception and knowledge of air pollution and its associated health risk were significantly different between different genders and the health status of the recruited individuals. There was a significant ( p <0.05) difference between male and female responses to smoke prevention in public areas and compromising on air pollution caused by China’s GDP growth, while there was no statistically significant difference between the genders’ awareness of air pollutants and their associated diseases/disorders. There was a significant difference between the subjects’ awareness based on age, excluding awareness of major air pollutants. Significant ( p <0.05) differences were observed between the respondents in the sampled cities, for all the sections of the questionnaire, which could be attributed to the differences in the levels of air pollution, access to media, and the local/provincial government’s outreach activities, such as seminars, symposia, and campaigns, regarding air pollution and its associated health risks. The differences in air pollution across the sampled cities could be caused by whether the city is a zone of production or consumption. Production sites are directly associated with trade (export/import, local/international), which elevates air pollution, as indicated by Wang et al. [ 12 ] and Zhang et al. [ 103 ]. Variations in the pollution level across China’s provinces could be caused by the county’s size. There are considerable differences between provinces, such as energy endowments and resources, lifestyles, population densities, and economic development. It was recently observed that, due to these factors, pollutants emissions increased rapidly in central China, while they stabilized or even decreased in coastal China [ 104 – 106 ].

A linear relationship between the knowledge or perceptions of air pollution’s adverse health impacts and literacy level has been reported [ 107 , 108 ]. Some studies also reported that there was a marked difference in the subjects’ knowledge and perception of air pollution between income classes [ 109 , 110 ]. Liu et al. [ 49 ] and Zhang [ 111 ] reported that women are more worried towards air pollution in China than men. In this study, there was a significant difference ( p <0.05) between the preventative measures adopted by male and female subjects; the female respondents were more cautious towards air pollution as they practiced more preventative measures, such as the use of respiratory masks, goggles/glasses, drinking more water, and consuming nutrient-rich meals to boost their immunity, as compared to males. Similarly, Kim et al. [ 63 ] reported that younger people were less satisfied with air quality than older people, while Liu et al. [ 49 ] reported opposite findings. This contradiction could be due to variations in the health conditions of the respondents, as healthier subjects were less concerned, and their tendency to travel, as subjects with travel experience were more concerned and anxious about air pollution and its associated health risks [ 49 ]. In this study, no significant difference was observed in the awareness of air pollution and its associated health risks between age groups, excluding awareness of major air pollutants, but a significant ( p <0.05) difference was observed between different age groups for awareness about toxic air pollutants.

The negative impacts of air pollution and its associated health risks can be minimized by increasing the public’s awareness. Internet sources (Baidu/blogs), social apps (Weibo/WeChat), and print or electronic media are useful tools for information transmission, exchange, and flow in China. By using such media, relevant literature and recommended practices against air pollution can be spread [ 112 ]. Similarly, informal communications; public conversations; discussions; and exchanging information between relatives, friends, and colleagues can also be vital in creating mass awareness and can positively influence the public’s risk perceptions. Health (doctors/physicians/other health care professionals) and social workers can also be included, as people often adopt health knowledge and practices from them. Based on this study, campaigns, seminars, symposia, and training about air pollution and its associated health risks should be arranged to increase awareness among the public and enable them of self-protection. Regular monitoring of air quality is suggested, as it can lead to fresh, clean, improved, and pollution-free air. During this study, the majority of the respondents reported television, their mobile phone, and the internet as their main sources of knowledge about air pollution and its associated health risks. The same response was reported by Liu et al. [ 49 ], however, Bickerstaff and Walker [ 113 ] reported that very few people selected media as their primary source of knowledge about air pollution. Although people do not check the air quality index on a regular basis, different reports, commentaries, and coverage about air pollution distributed through the internet, television, newspapers, radio, and magazines are educating people; changing their perception, attitude, and practices towards air pollution; and increasing their awareness of air pollution and its associated adverse health risks.

We attempted to approach as many subjects and to extend the study as broadly as possible, but, as other surveys, we faced some limitations (funding, time, and survey duration). Although the study covered 13 major Chinese cities, there are few rapidly developing cities that should also be surveyed. The current study was embodied to Chinese students only, so involving people other than the students is suggested in future studies. Moreover, for mental and behavioral health, the individual baseline physiological conditions were not adjusted on account of limited time frame, and tight schedule of Chinese students. Furthermore, the administered questionnaire contained closed-ended questions, therefore the responses were “as per asked” by the given questions. Therefore, surveying with an open-ended questionnaire is required to further extend our understanding of the population’s perceptions, attitudes, knowledge, and awareness level, and the problems they face, to determine how their consciousness towards self-protection can be enhanced. These key points must be considered before conducting this study in another area, and these findings should be cautiously applied to another location and population.

In conclusion, the recruited respondents have suffered from different, adverse physical effects, such as respiratory infections or problems (lung cancer, asthma), and different types of ENT illnesses, due to haze and air pollution. Owing to the current air pollution scenario, almost all of the recruited subjects used face/respiratory masks, some used eyeglasses/goggles to prevent the negative impacts of haze and air pollution, and many ensured that they drank enough water to avoid dehydration and remove toxins. The most severe responses to air pollution were psychologically-associated behavioral problems, indicating a serious threat to mental health, and behavioral vulnerability and variations induced by stress, depression, anxiety, shortened tempers, mood swings, and unpleasant moods. The respondents were aware of major air pollutants, their sources, and the adverse effects of haze and air pollution. Televisions, cell phones, and the internet were the primary sources of knowledge about air pollution and its associated health effects.

Governmental, such as environmental protection agencies, and non-governmental organizations should adopt effective communication styles to educate the public and increase their awareness and understanding of the health risks associated with air pollution at individual, family, and community levels. This will encourage them to adopt preventative measures, and safeguard themselves. This will also maximize the understanding of the public’s risk perceptions, which in turn will not have a negative effect on their behavior. The air quality assessment program should be extended to other parts of China, such as developing cities, which will aid in the acquisition of transparent data regarding air quality parameters in these sites, and will aid the development of proper strategies and plans to improve air quality across China. Coordination between governmental organizations and provincial governments, and their support to the central government is necessary and recommended for developing emission control policies to ensure that future generations do not face these problems.

Supporting information

Table A. Bonferroni Adjustments to remove family wise error inflation. Table B. Interquartile ranges for the air pollutants across the sampled cities (Oct 2016—March 2016). Table C. Reported gender & city-dependent behavioral and psychological effects of air pollution. Table D. Age-dependent behavioral and psychological effects of air pollution on the recruited respondents. Table E. Gender- and city-dependent adoption of practices to prevent the adverse effects of air pollution. Table F. Age-dependent adoption of practices to prevent the adverse effects of air pollution. Table H. Gender- and city-dependent awareness and perceptions of air pollution. Table G. Age-dependent awareness and perception of air pollution.

Acknowledgments

Sincere thanks to the National Natural Science Foundation (No. 31772470) of China in supporting the study financially. We are thankful to Dr. Xiaoguang Qi, Dr. Xinkang Bao, Dr. Donglai Li, Dr. Bingwan Liu, Dr. Aichun Xu, Dr. Min Chen, Dr. Zuofu Xiang, Dr. Zhenhua Luo, Dr. Junhua Hu, Dr. Aiwu Jiang, Dr. Yang Liu, Miss Runyang Zhang, Mr. Yunchao Luo, and Miss Lin Wang for their help in data collection. We also thank all the respondents, who participated in this survey and extend our meek thanks to Mr. Shoaib Khalid (Ph.D. (GIS) student, Nanjing University) for digitizing the map.

Funding Statement

Sincere thanks to the National Natural Science Foundation (No. 31772470) of China in supporting the study financially to ZL. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Data Availability

Records smashed – new WMO climate report confirms 2023 hottest so far

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Records were once again broken for greenhouse gas levels, surface temperatures, ocean heat and acidification, sea level rise, ice cover and glacier retreat, a new global report issued by the UN weather agency (WMO) on Tuesday shows.

Heatwaves, floods, droughts, wildfires and rapidly intensifying tropical cyclones caused misery and mayhem, upending everyday life for millions and inflicting many billions of dollars in economic losses, according to the WMO State of the Global Climate 2023 report .

“ Sirens are blaring across all major indicators ... Some records aren’t just chart-topping, they’re chart-busting. And changes are speeding up,” said UN Secretary-General António Guterres in a video message for the launch.

Based on data from multiple agencies, the study confirmed that 2023 was the warmest year on record, with the global average near-surface temperature at 1.45°C above the pre-industrial baseline. It crowned the warmest ten-year period on record.

“The scientific knowledge about climate change has existed for more than five decades, and yet we missed an entire generation of opportunity ,” WMO Secretary-General Celeste Saulo said presenting the report to the media in Geneva. She urged the climate change response to be governed by the “welfare of future generations, but not the short-term economic interests”.  

“As Secretary-General of the World Meteorological Organization, I am now sounding the red alert about the state of the global climate,” she emphasised. 

World in disarray 

However, climate change is about much more than air temperatures, the WMO experts explain. The unprecedented ocean warmth and sea level rise, glacier retreat and Antarctic sea ice loss, are also part of the grim picture. 

On an average day in 2023, nearly one third of the ocean surface was gripped by a marine heatwave, harming vital ecosystems and food systems, the report found. 

The glaciers observed suffered the largest loss of ice on record – since 1950 – with extreme melt in both western North America and Europe, according to preliminary data. 

Alpine ice caps experienced an extreme melting season, for instance, with those in Switzerland loosing around 10 per cent of their remaining volume in the past two years. 

The Antarctic sea ice loss was by far the lowest on record – at one million square kilometres below the previous record year – equivalent to the size of France and Germany combined .

Observed concentrations of the three main greenhouse gases – carbon dioxide, methane, and nitrous oxide – reached record levels in 2022 and continued increase in 2023, preliminary data shows. 

Global repercussions

According to the report, weather and climate extremes are either the root cause or serious aggravating factors that in 2023 triggered displacement, food insecurity, biodiversity loss, health issues and more.

The report, for example, cites figures that the number of people who are acutely food insecure worldwide has more than doubled, from 149 million before the COVID-19 pandemic to 333 million in 2023 in 78 countries monitored by the World Food Programme ( WFP ).

“The climate crisis is the defining challenge that humanity faces. It is closely intertwined with the inequality crisis – as witnessed by growing food insecurity and population displacement, and biodiversity loss,” said Ms. Saulo.

A glimmer of hope

The WMO report not only raises alarm but also offers reasons for optimism. In 2023, renewable capacity additions soared by almost 50 per cent, totalling 510 gigawatts (GW) - the highest observed rate in two decades. 

The surge in renewable energy generation, primarily fuelled by solar radiation, wind, and the water cycle, has positioned it as a leading force in climate action for achieving decarbonization goals.

Effective multi-hazard early warning systems are crucial for mitigating the impact of disasters. The  Early Warnings for All initiative aims to ensure universal protection through early warning systems by 2027. 

Since the adoption of the Sendai Framework for Disaster Risk Reduction , there has been an increase in the development and implementation of local disaster risk reduction strategies.

From 2021 to 2022, global climate-related finance flows nearly doubled compared to 2019-2020 levels, reaching nearly $1.3 trillion . 

However, this amounts to only about one percent of global GDP, underscoring a significant financing gap. To achieve the objectives of a 1.5°C pathway, annual climate finance investments must increase more than sixfold, reaching almost $9 trillion by 2030, with an additional $10 trillion needed by 2050.

Cost of inaction

The cost of inaction is staggering, the report warns. Between 2025 and 2100, it may reach $1,266 trillion , representing the difference in losses between a business-as-usual scenario and a 1.5° C pathway. Noting that this figure is likely a significant underestimate, the UN weather experts call for immediate climate action. 

The report is launched ahead of the Copenhagen Climate Ministerial meeting, where climate leaders and ministers from around the world will gather for the first time since  COP28 in Dubai to push for accelerated climate action, including delivering an ambitious agreement on financing at COP29 in Baku later this year – to turn national plans into action.

• climate action

ORIGINAL RESEARCH article

Time-series analysis of the association between air pollution exposure and outpatient visits for dry eye disease: a case study in zhengzhou, china.

• 1 Henan Eye Institute & Henan Eye Hospital, Henan Provincial People’s Hospital, People’s Hospital of Zhengzhou University, Zhengzhou, China
• 2 Hospital-Acquired Infection Control Department, School and Hospital of Stomatology, Wenzhou Medical University, Wenzhou, China

Background: Dry eye disease (DED) is a prevalent ocular surface disease that significantly impacts patients’ quality of life. The association between air pollution and the risk of dry eye disease remains uncertain.

Methods: Data on outdoor air pollutants, meteorological information, and outpatient visits for DED were collected from July 1, 2014, to December 31, 2019. The relationship between ambient air pollutants and DED outpatient visits was analyzed using a generalized additive model with a Poisson distribution.

Results: Among the 5,204 DED patients included in the study, 63.76% were female and 36.24% were male. The single-pollutant model revealed a significant association between a 10 μg/m 3 increase in concentrations of fine-particulate matter with a median aerometric diameter of less than 10 μm (PM 10 ), sulfur dioxide (SO 2 ), nitrogen dioxide (NO 2 ), and carbon monoxide (CO) and outpatient visits for DED. Fine-particulate matter with a median aerometric diameter of less than 2.5 μm (PM2.5) showed a significant association with DED outpatient visits in males and the 19–59 years age group. The strongest associations between air pollutants and outpatient visits were observed in male patients and during the cold season.

Conclusion: The noteworthy correlation between air pollutants and DED outpatient visits can offer evidence for policy makers and underscore the significance of reinforcing environmental protection.

1 Introduction

Dry eye disease (DED) is a prevalent ocular surface disease that presents with symptoms such as ocular surface discomfort, fatigue, impaired vision, and tear film instability, significantly impacting the quality of life of million of individuals globally ( 1 ). DED is a multifactorial ocular surface disease caused by an imbalance in tear film homeostasis, resulting in tear film hyperosmolarity, instability, ocular surface inflammation and injury, as well as neurosensory abnormalities ( 2 ). Common symptoms of DED encompass excessive mucus production, tear film evaporation impairment, itching, burning, light sensitivity-induced redness, and eyelid movement difficulty ( 3 ). From 1997 to 2021, the estimated global prevalence of DED was 11.59%, with East Asia exhibiting the highest prevalence at 42.8% ( 4 ). Therefore, DED has emerged as a significant and escalating public health concern.

Air pollution is a significant global public health issue, as evidenced by numerous epidemiological studies demonstrating its association with a substantial increase in outpatient visits ( 5 ) and mortality rates ( 6 ). However, the majority of studies have primarily concentrated on the respiratory system’s response to air pollution, leaving the impact on ocular health relatively neglected. Extended exposure of ocular surfaces to air pollutants heightens their vulnerability to these substances ( 7 ). Both air pollutants and weather conditions have the potential to impact the health of the tear film and ocular surface, disrupting the eye’s natural lubrication and protective mechanisms. Prolonged exposure to air pollution can result in various symptoms of ocular surface diseases, such as ocular discomfort, abnormal tear film structure, and inflammation of the ocular surface ( 8 – 10 ). The extent to which long-term exposure to high levels of air pollution affects the eye is not fully understood. Nevertheless, heightened levels of air pollution might be linked to greater instability of the tear film ( 11 , 12 ). The association between air pollution and allergic conjunctivitis has been confirmed ( 5 , 13 ). Allergic conjunctivitis, characterized by the release of numerous inflammatory mediators, leads to deficiencies in the mucus layer and instability of the tear film, making it a major contributing factor to DED ( 14 ). Limited research has been conducted on the prolonged exposure of the ocular surface to outdoor air pollutants. Only a handful of studies have explored the impact of air pollution on the ocular surface ( 9 , 15 – 19 ). Ocular surface abnormalities associated with air pollution are regarded as a subset of DED due to their distinctive features, including tear film abnormalities, elevated ocular surface disease index, and reduced conjunctival goblet cell density ( 9 , 17 , 18 ). The majority of studies investigating the impact of air pollution on the ocular surface have been limited by short study durations and a narrow range of air pollutants examined, potentially contributing to inconsistent findings influenced by factors such as geographical location and population disparities. This study examined the relationship between outdoor air pollutants, including fine-particulate matter with a median aerometric diameter of less than 2.5 μm (PM 2.5 ), fine-particulate matter with a median aerometric diameter of less than 10 μm (PM 10 ), sulfur dioxide (SO 2 ), nitrogen dioxide (NO 2 ), carbon monoxide (CO), ozone (O 3 ) and outpatient visits for DED in Zhengzhou, China. The study also accounted for potential confounding meteorological factors. This study establishes a foundation for understanding the link between air pollution exposure and dry eye disease, thereby supporting the development of enhanced prevention and intervention strategies.

2 Materials and methods

2.1 study area.

Zhengzhou is a significant central city and a comprehensive transportation hub in central China. Situated south of the North China Plain, north of central Henan Province, and downstream of the Yellow River, Zhengzhou serves as both the capital of Henan Province and the core city of the Central Plain Urban Agglomeration. Zhengzhou experiences a northern temperate continental monsoon climate, characterized by frequent shifts between cold and warm air masses, as well as four distinct seasons: spring, summer, autumn, and winter. Our study area is the five primary urban areas of Zhengzhou City ( Figure 1 ). Zhengzhou is administratively divided into six districts: Zhongyuan, Erqi, Huiji, Guancheng Hui, Jinshui and Shangjie. Shangjie District, situated in the northwest and distant from the city center, was excluded from the study due to the inaccessibility of hospitals, pollution monitoring stations, and data accuracy concerns.

Figure 1 . Locations of environmental monitoring stations and hospitals in Zhengzhou, China.

2.2 Data sources

The disease data were collected from the Henan Eye Hospital, which is a branch of the Dry Eye and Ocular Surface Diseases Center and serves as the National Level Dry Eye Demonstration and Guidance Center. The patient information regarding dry eye visits to this hospital was obtained from the hospital information management system for the period of July 1, 2014, to December 31, 2019. The majority of patients who visited the dry eye clinic at the ophthalmology department of the hospital were residents of Zhengzhou. Patients residing outside the study area were excluded to ensure that the study subjects were part of the permanent population within the study area. The diagnosis of DED was based on the standardized International Classification of Diseases-10th Revision (ICD-10) code for ophthalmology, specifically H11.103. We reviewed outpatient medical records and conducted ophthalmic examinations to confirm the diagnosis of DED and related complaints. The final diagnostic information was reviewed by either a mid- or senior-level physician in the department or the attending physician with expertise in the field to ensure the accuracy of diagnosis and data classification. The dataset only contains basic outpatient information, patient identification numbers (each patient has a unique number for identification purposes), visit dates, age, gender, and home addresses (including ZIP codes). Informed consent was not required because the data came from anonymous datasets typically used for administrative purpose.

Meteorological data including average daily temperature, average daily pressure, average daily wind speed, and average daily relative humidity in Zhengzhou City from July 1, 2014 to December 31, 2019 were obtained from the National Meteorological Science Data Center. 1

Air pollution data were collected from nine national air monitoring stations: Tobacco Factory Station, Zheng Textile Machine Station, Bank School Station, Water Supply Company Station, Jingkai District Management Committee Station, Forty-seventh Middle School Station, Municipal Monitoring Station, Medical College Station, and Gangli Reservoir Station ( Figure 1 ). The daily average concentrations of PM 2.5 and PM 10 were measured using the tapered element oscillating microbalance (TEOM) method. Ultraviolet fluorescence and chemiluminescence methods were used to measure SO 2 and NO 2 . An infrared (IR) analyzer and a non-dispersive ultraviolet fluorescence photometer were employed to measure CO and O 3 , respectively. Air pollutant concentrations at each monitoring site were collected from July 1, 2014, to December 31, 2019. The pollutants included PM 2.5 , PM 10 , SO 2 , NO 2 , CO, and O 3 . Hourly concentrations were recorded for PM 10 , SO 2 , NO 2 , and CO, with daily averages calculated. O 3 concentration was determined as the 8-h maximum. The air pollution data are stored in the database along with daily meteorological data and outpatient visit data.

2.3 Data analysis

We used the Spearman correlation coefficient to assess the correlation between air pollutants and meteorological factors. Daily outpatient visits for DED are rare events that approximately follow a quasi-Poisson distribution. To assess the effect of air pollutant exposure on DED outpatient visits, we employed a combination of a quasi-Poisson generalized additive model (GAM) and a distributional lag nonlinear model (DLNM) ( 20 ). All models control for the effects of confounding variables, including meteorological factors, by smoothing using natural cubic spline curves (ns) with three degrees of freedom (df). Dummy variables were used to control for variables that may have potential effects, such as day-of-week and holiday effects. To assess the potential lagged effects of air pollutants, we defined same-day exposure as lag 0 and considered a maximum lag period of 7 days. We separately examined the effects of single-day lags (lag 0 to lag 7) and cumulative lags (lag 0–1 to lag 0–7) of air pollution. The choice of df is determined based on the principle of residual independence, which selects the minimum value of the sum of the absolute values of the partial autocorrelation function (PACF) of the residuals from the base model. The final model is shown below:

The variables in the model are defined as follows: Y t i represents the actual number of hospital admissions on day t ; μ t represents the expected value of hospital admissions on day t ; X t represents the concentration of air pollutants (PM 2.5 , PM 10 , CO, SO 2 , NO 2 , O 3 ) on day t ; β is the regression coefficient; ns represents the natural cubic spline; d f t represents the degrees of freedom; Z t represents the meteorological factors (mean temperature, mean air pressure, mean relative humidity, and mean wind speed) on day t ; DOW represents the weekly dummy variable, and α is a constant term. The lag model determines the optimal lag period based on the maximum odds ratio and the minimum p -value. Sensitivity analyses of the main results were conducted by varying the df of the time variable and the degrees of freedom of the mean temperature, air pressure, relative humidity, and wind speed. Statistical significance was defined as a p -value less than 0.05.

To investigate potential modifying factors, patients were categorized into two gender groups (male and female) and three age groups (0–18, 19–59, and ≥ 60 years). Additionally, considering the seasonal characteristics of Zhengzhou, the year was divided into two seasons: the warm season (April to September) and the cold season (January to March and October to December).

Table 1 presents the descriptive statistics of daily outpatient visits for DED at Henan Provincial Eye Hospital, including meteorological factors. Among the 5,204 outpatient visits for dry eye syndrome, there were 1886 visits (36.24%) by males and 3,318 visits (63.76%) by females. Regarding age groups, there were 315 visits (6.05%) in the 0–18 age group, 2,546 visits (48.92%) in the 19–59 age group, and 2,343 visits (45.02%) in the 60 and above age group. Among the 5,204 DED patients included in this study, females accounted for a larger proportion (63.76%) compared to males. Patients aged 0–18 years constituted the smallest age group (6.05%), and the warm season had a slightly higher seasonal distribution (52.67%) compared to the cold season. The average values of mean temperature, air pressure, relative humidity, and wind speed were 16.44°C, 1045.0 hPa, 62.21%, and 2.52 m/s, respectively.

Table 1 . Descriptive statistics for meteorological variables, and dry eye disease visits from July 1, 2014, to December 31, 2019, in Zhengzhou, China.

Figure 2 illustrates the time-series patterns of air pollutants and dry eye visits throughout the study period. The air pollutants exhibited a distinct seasonal trend, with the lowest concentrations occurring during summer and the highest concentrations during winter.

Figure 2 . Time-series plot of daily outpatient visits for dry eye disease and corresponding daily air pollution concentrations in Zhengzhou, China, from July 1, 2014, to December 31, 2019.

We analyzed the association between air pollutants and outpatient visits for DED using a single-pollutant model. We investigated the relationship between individual air pollutants and the number of outpatient visits for DED, with meteorological factors included as covariates. The specific meteorological factors considered were mean temperature, air pressure, relative humidity, and wind speed. Figure 3 demonstrates a significant association between a 10 μg/m 3 increase in PM 10 , CO, SO 2 , and NO 2 concentrations and outpatient visits for DED. Both PM 10 and CO exhibited a significant association with an increase in DED visits for every 10 μg/m 3 increase in concentrations, considering all lags from 0 to 7 days, in contrast to cumulative lags from 0–1 to 0–7 days. Significant associations were observed between SO 2 and DED outpatient visits, considering lags of 1, 2, 3, 0–1, 0–2, 0–3, 0–4, 0–5, and 0–6 days, as well as between NO 2 and DED outpatient visits, considering lags of 0, 1, 0–1, 0–2, and 0–3 days. The results of the cumulative lag (0–1 to 0–7 days) modeling suggest that continuous exposure to these air pollutants may lead to an increased number of DED visits. The analysis using the single-pollutant model did not provide evidence of an association between DED outpatient visits and PM 2.5 or O 3 .

Figure 3 . Relative risk of dry eye disease outpatient visits associated with a 10 μg/m 3 increase in air pollutant levels across single-day lags (lag 0, 1, 2,…,7 days) and cumulative lags (lag 0–1, 0–2, 0–3,…, lag 0–7 days).

Considering the inevitable interactions between air pollutants, we employed multi-pollutant modeling for the analysis. Previous research has demonstrated a strong correlation between PM 2.5 and PM 10 ( 21 ). PM 10 was included in the multi-pollutant model due to the lack of evidence for an association between PM 2.5 and DED visits in the single-pollutant model analysis. The model incorporated meteorological variables as covariates, while pollutant levels within the optimal lag zone were selected as control variables. Even after adjusting for confounding factors, both PM 10 and CO exhibited a strong association with DED outpatient visits, and the number of DED outpatient visits was also associated with NO 2 levels. There was no significant association between the pollutants PM 2.5 , O 3 , and SO 2 and DED outpatient visits. The lack of a significant association between SO 2 and DED outpatient visits contrasts with the findings of the single-pollutant model ( Table 2 ).

Table 2 . Association between air pollutants and outpatient visits for dry eye disease: a multipollutant model.

Additionally, we examined the relationship between various air pollutants and DED outpatient visits across different population groups. Among males, elevated levels of PM 2.5 , PM 10 , CO, SO 2 , and NO 2 were significantly linked to DED outpatient visits, while in females, only PM 10 and CO showed significant associations with DED outpatient visits. Within the age group of 0–18 years, higher CO concentrations were significantly associated with DED outpatient visits. Within the age group of 19–59 years, elevated levels of PM2.5, PM10, and CO showed significant associations with DED outpatient visits. Within the age group of 60 and above, increasing concentrations of PM 10 , CO, and NO 2 were significantly associated with outpatient visits for DED. Within the seasonal stratification, higher PM 10 and CO concentrations during the warm season showed a significant association with DED outpatient visits. Moreover, increased levels of PM 10 , CO, SO 2 , and NO 2 during the cool season were significantly associated with DED outpatient visits ( Table 3 ).

Table 3 . Correlation between air pollutants and outpatient visits for dry eye disease, and effect modification assessed through stratified analyses by patient characteristics.

4 Discussion

This study found a significant association between air pollutants (PM 2.5 , PM 10 , CO, SO 2 , NO 2 ) and outpatient visits for DED. A lag effect was observed in the potential association between PM 10 , CO, SO 2 , and NO 2 and outpatient visits for DED. Among the gender stratified groups, females accounted for a larger proportion (63.76% of total study patients). Nevertheless, the association between air pollutants and the number of outpatient visits for DED was more pronounced in males compared to females. The association between air pollutants and the number of outpatient visits for DED varied across different age groups. The association between air pollutants and DED outpatient visits was more pronounced during the cold season compared to the warm season.

Previous studies have demonstrated the significant impact of air pollution on DED development, utilizing optical thickness measurements to assess aerosol concentrations in the atmosphere ( 22 ). Nevertheless, the association between air pollutants and DED exhibits variability across different studies. Discrepancies in study findings may arise due to variations in geographical regions, methodologies employed, and characteristics of the study populations. Our study revealed a significant association between a 10 μg/m 3 increase in PM 10 concentration and DED outpatient visits. Furthermore, PM 2.5 exhibited a significant association with DED outpatient visits in males and the 19–59 years age group. It is worth noting that PM has the potential to induce ocular surface inflammation ( 23 ), which is considered a key component of DED in both humans ( 24 ) and animal models ( 25 ). Although most of the relevant studies, have found an association between PM and DED ( 3 , 20 , 26 ), there are individual studies that have shown no association between PM and DED ( 8 , 18 ).

Similarly, not all studies have demonstrated an association between gaseous pollutants (SO 2 , NO 2 , CO, and O 3 ) and DED ( 8 , 26 – 28 ). However, our study identified significant associations between a 10 μg/m 3 increase in CO, SO 2 , and NO 2 concentrations and DED outpatient visits. This finding aligns with the results of a study conducted in Hangzhou, China ( 26 ), which did not identify an association between O 3 and DED. The mechanisms underlying the potential impact of gaseous pollutants on ocular surface health are not fully comprehended. However, insights can be gleaned from extraneous data, which demonstrate that exposure to reactive gases outside the eye can induce cell death, oxidative stress, and inflammation ( 9 , 29 ).

Our study differs from existing studies due to three potential reasons. Firstly, variations in climates and environments across different regions may have resulted in different effects of individual air pollutants on DED. Secondly, differences in study populations, along with variations in ocular surface physiology among populations, contribute to the complexity of clinical presentations. Thirdly, variations in study designs and methods can introduce bias into the results. In the present study, we employed GAM and time series modeling, with each patient serving as their own control. The model accounted for potential holiday effects, day of the week effects, and meteorological factors (e.g., mean temperature and mean humidity), ensuring more accurate results. In conclusion, our study provides additional evidence supporting the role of air pollution in the increasing prevalence of DED.

In the lag analysis of the single-pollutant model, the peak effects on DED outpatient visits were observed at specific lags: PM 10 at lag 6, CO at lag 5, SO 2 at lag 2, and NO 2 at lag 1 ( Figure 3 ). The lag effect on DED patients may be part of the underlying mechanism for the development of dry eye. The ocular surface has a certain level of tolerance to environmental changes, and only when this tolerance threshold is exceeded, the stability of the tear film on the ocular surface decreases, resulting in various ocular discomforts. Cumulative lag effect analysis revealed a more pronounced cumulative lag effect of PM 10 and CO on the number of DED outpatient visits. The effect gradually increased from lag 0–1 to lag 0–7, indicating that continuous exposure to high concentrations of PM 10 and CO may contribute to an increased number of DED outpatient visits.

Studies have consistently demonstrated that women are more susceptible to DED compared to men, and sex hormones may act as predisposing factors for the condition. Androgens enhance the function of the meibomian glands by promoting oil secretion onto the ocular surface, thus preventing tear evaporation. However, the effects of estrogen and progesterone on meibomian gland function may counteract the influence of androgens ( 30 ). While the precise effects of estrogen and progesterone on the ocular surface are not yet fully understood, estrogen has been implicated in contributing to inflammation of the ocular surface. Therefore, this study further supports the notion that women are a susceptible population for DED.

Air pollution may have indirect effects on the eyes. For example, fine particulate matter from air pollution can enter the lungs and cause an inflammatory response, which in turn affects circulation and the immune system throughout the body. These changes may have a negative impact on the health of the eye surface. A study in Latin America looked at the effects of air pollutants in multiple cities on cardiovascular and respiratory mortality in adults. The study showed that the increase in mortality risk was greater in men across gender groups, and that the effects of air pollutants on the cardiovascular and respiratory systems may be greater in men ( 31 ). Relatively few studies have addressed the relationship between air pollution, ocular surface disease and gender differences. Our study showed that the association between air pollutants and outpatient visits for DED was stronger in men than in women. This may be related to male lifestyle and behavioral habits, for example, men are more likely to engage in outdoor work and activities, thus increasing eye exposure to pollutants. This reason is only speculative, and the interpretation of this result in this study lacks some supporting evidence, and further studies are needed to explore in depth the gender-differentiated effects of air pollution on ocular surface diseases and their mechanisms.

The lifestyle habits of different age groups vary considerably, which may explain the difference in outpatient visits for DED and associated air pollutants for different age groups. Children’s activities are mainly indoors (home or classroom), and air pollutant data from urban monitoring sites were used in this study, so the results showed fewer air pollutants associated with them. DED patients in the 0–18 years age group are more likely to be associated with the overuse of electronic devices in modern society ( 32 ) or the habit of wearing contact lenses in the younger age group ( 33 ). Older individuals may be more sensitive to air pollution, thus increasing the risk of dry eye ( 34 ). But the intrinsic reasons for the difference in outpatient visits for DED and associated air pollutants for different age groups are not clear, and we need more studies to prove it. Of course, ecological studies can only provide a hypothesis for the association, and it cannot be ruled out that different studies may yield different results, so the results should be interpreted with caution.

In the seasonal stratified analysis, air pollutants (PM 10 , CO, SO 2 , and NO 2 ) showed a significant association with DED outpatient visits during the cool season. During the warm season, only PM 10 and CO exhibited a significant association with DED. This may be attributed to the increased sensitivity of the ocular surface to air pollutants in colder temperatures. Higher outdoor humidity demonstrated a protective association with DED symptoms ( 8 ), whereas wind speed and sunshine hours were identified as risk factors for DED diagnosis ( 35 ). Zhengzhou city experiences a warm temperate continental climate characterized by dry, cold winters with limited precipitation, as well as low rainfall and wind in spring. Hence, the unique climate conditions contribute to a stronger association between air pollutants and the number of DED outpatient visits during the cold season.

This study had several limitations. Firstly, it was designed as an ecological study, which only allows for drawing conclusions regarding possible associations, limiting the ability to make causal inferences. Secondly, the measured air pollutant concentrations at air quality monitoring stations may not accurately represent individual exposure levels. Future cohort studies assessing air pollution exposure are necessary to further validate the impact of air pollution on eye health. Lastly, the clinical data used in this study were obtained solely from a single large hospital, which is representative but has inherent limitations. The influencing factors of DED are complex. In the future, our goal is to conduct more in-depth analyses using different research designs such as case–control studies and cohort studies. These approaches will allow us to accurately assess individual exposure levels and thoroughly consider various factors, including lifestyle, age, gender, and medical history.

5 Conclusion

This study investigated the relationship between outpatient visits for DED and air pollution levels in Zhengzhou, China. The results demonstrated significant associations between DED outpatient visits and PM 2.5 , PM 10 , CO, SO 2 , and NO 2 . These associations exhibited gender and seasonal variations, with a particularly strong association observed during the cold season, with males being the most susceptible. While air pollution may serve as a potential risk factor for DED, our findings establish an association without establishing causation. Considering the rapid economic and industrial development in the region, implementing robust environmental protection strategies to mitigate air pollution is crucial for safeguarding eye health.

Data availability statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Ethics statement

Ethical approval was not required for the study involving humans in accordance with the local legislation and institutional requirements. Written informed consent to participate in this study was not required from the participants or the participants’ legal guardians/next of kin in accordance with the national legislation and the institutional requirements.

Author contributions

MX: Investigation, Software¸ Writing – original draft. YY: Investigation, Methodology, Software, Writing – original draft. JS: Data curation, Investigation, Methodology, Writing – review & editing. RH: Investigation, Methodology, Writing – original draft. YH: Formal analysis, Investigation, Writing – original draft. MZ: Methodology, Software, Writing – review & editing. XY: Data curation, Resources, Supervision, Writing – review & editing.

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. We acknowledged the financial support from the Joint Construction Project of Henan Provincial Medical Science and Technology Tackling Program (LHGJ20220094).

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

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Keywords: dry eye disease, generalized additive model, air pollution, outpatient visits, ocular surface disease

Citation: Xia M, Yang Y, Sun J, Huang R, Huang Y, Zhang M and Yao X (2024) Time-series analysis of the association between air pollution exposure and outpatient visits for dry eye disease: a case study in Zhengzhou, China. Front. Public Health . 12:1352057. doi: 10.3389/fpubh.2024.1352057

Received: 07 December 2023; Accepted: 04 March 2024; Published: 14 March 2024.

Reviewed by:

Copyright © 2024 Xia, Yang, Sun, Huang, Huang, Zhang and Yao. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Mengqi Zhang, [email protected] ; Xi Yao, [email protected]

Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.