AIR POLLUTION STUDIES
USC studies show that clean air matters for a healthy brain
Research on air pollution and cognitive decline indicate cleaner air may reduce risk for Alzheimer’s and other dementias
Peer-Reviewed PublicationTwo USC researchers whose work linked air pollution to a greater risk of Alzheimer’s disease and faster cognitive decline are seeing signs that cleaner air can make a difference in brain health.
Cars and factories produce a fine particulate known as PM2.5 that USC-led studies have linked to memory loss and Alzheimer’s disease. Smaller than the width of a human hair, these tiny particles pose a big problem. Once inhaled, they pass directly from the nose up and into the brain, beyond the blood-brain barrier that normally protects the brain from dust or other invaders.
In a research letter published today in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, the USC researchers described how their labs each independently reported indications of recent decreases in neurotoxicity (damage to the brain or nervous system caused by exposure to toxic substances) of PM2.5 air pollution in humans and mice.
University Professor Caleb Finch and associate professor of gerontology and sociology Jennifer Ailshire, both with the USC Leonard Davis School of Gerontology, focused on PM2.5 pollution. Long-term exposure to PM2.5 has been linked to premature death, particularly in people with chronic heart or lung diseases.
Ailshire’s research, published earlier this year in the Journal of Alzheimer’s Disease, showed a strong association between cognitive deficits and air pollution among people with lower levels of education in 2004.
Based on data from the nationwide Health and Retirement Study, her work showed that, when exposed to PM2.5, adults 65 and older who had fewer than eight years of education faced a greater risk of cognitive impairment. But one decade later, Ailshire found no such association for study participants.
A likely factor was the reduction in PM2.5 over the prior decade, said Ailshire. Air quality data showed the average annual PM2.5 levels in the study participants’ neighborhoods were 25% below 2004 levels.
Notably in 2014, very few of the study participants lived in places with annual average PM2.5 that exceeded U.S. Environmental Protection Agency air quality standards. This further suggested that the improvements with cognitive decline were linked to a drop in exposure to high pollution among older adults.
“Improving air quality around the country has been a tremendous public health and environment policy success story. But there are signs of a reversal in these trends,” Ailshire said. “Pollution levels are creeping up again and there are increasingly more large fires, which generate a significant amount of air pollution in certain parts of the country. This gives me cause for concern about future trends in improving air quality.”
Finch’s research on mice, published earlier this year in the Journal of Alzheimer’s Disease, also found evidence of lower neurotoxicity of air pollution over time.
Finch and his research team have studied pollution levels at the same Los Angeles site and their effect on mouse brains since 2009. After 2017, the mice exposed to a tiny, nanoscale version of PM2.5 appeared healthier. Markedly, they showed sharp declines in several factors of neurotoxicity, including oxidative damage to cells and tissues.
During the years that Finch’s and Ailshire’s studies were taking place, the composition of air pollution in the United States was also changing.
From 2000 to 2020, PM2.5 levels declined nationwide by 41%, according to the EPA. In contrast, urban PM2.5 in Los Angeles declined only slightly from 2009 to 2019. While nationwide ozone levels decreased, Los Angeles County ozone reversed the prior trends by increasing after 2015.
Finch and Ailshire emphasize that their findings cannot evaluate potential benefits of air pollution improvements to the risk of cognitive decline and dementia. Although PM2.5 levels declined nationally from 2009 to 2016, the year-over-year increases that have been observed since 2017 show that improvements in air quality can be reversed, as they were in Los Angeles.
“Our findings underscore the importance of efforts to improve air quality as well as the continued importance of demographic and experimental evaluation of air pollution neurotoxicity,” Finch said.
Finch and Jiu-Chiuan “J.C.” Chen, an associate professor of preventive medicine at the Keck School of Medicine of USC, previously published a study using both human and animal data that showed brain aging processes worsened by air pollution may increase dementia risk. Their research indicated that older women who lived in locations with high levels of PM2.5 suffered memory loss and Alzheimer’s-like brain shrinkage not seen in women living with cleaner air.
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METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
People
ARTICLE TITLE
Recently decreased association of air pollution with cognitive impairment in a population‐based aging cohort and in a mouse model
ARTICLE PUBLICATION DATE
7-Oct-2021
Smoggier skies, lower scores?
A Brazilian study examines the effects of air pollution on students’ cognitive performance
A new study published in the Journal of the Association of Environmental and Resource Economists looks at the causal relationship between outdoor air pollution levels on nationwide university entry examination day and students’ cognitive performance in Brazil.
In “The Effects of Air Pollution on Students’ Cognitive Performance: Evidence from Brazilian University Entrance Tests,” authors Juliana Carneiro, Matthew A. Cole, and Eric Strobl use Brazilian data on concentrations of ozone (O3) and particulate matter (PM10) and a data set of students’ scores to examine the impact of air pollution on academic performance in national examinations. The air pollution data focuses on Rio de Janeiro and São Paulo—Brazil’s most industrialized states—using air pollution and weather monitoring station data to build a unique data panel from 2015–17.
The authors constructed individual-level panel data for the two days of exams across three years and applied student fixed effects to address potential endogeneity concerns. “In addition,” they note, “We take advantage of plausibly exogenous spatial and temporal variation in PM10 across municipalities in the states of Rio de Janeiro and São Paulo and utilize an instrumental variable approach based on wind direction.”
The findings suggest that an increase of 10 micrograms per cubic meter (mg/m3) of PM10 on the day of the examination decreases students’ scores by 6.1 points (8% SD). “Even when including a more flexible measure of our treatment that is utilizing a dummy variable to account for the days in which PM10 exceeded the WHO’s acceptable threshold, our findings still point to negative effects of air pollution on cognitive performance during examinations,” they note. Placebo tests, sensitivity checks, and falsifications tests reinforced the main findings: evidence of a link between air pollution and exam performance.
Consistent with previous studies, the authors also find evidence that the effect of air pollution on exam performance appears to affect males more adversely than females. “Our results also suggest that poorer students may be more susceptible to air pollution than wealthier exam takers,” they write, adding, “Our findings provide plausible evidence to suggest that cognitive performance may be hindered by poor air quality, but unequally so.”
JOURNAL
Journal of the Association of Environmental and Resource Economists
METHOD OF RESEARCH
Data/statistical analysis
SUBJECT OF RESEARCH
People
ARTICLE TITLE
The Effects of Air Pollution on Students’ Cognitive Performance: Evidence from Brazilian University Entrance Tests
ARTICLE PUBLICATION DATE
16-Aug-2021
Pollution from freight traffic disproportionately impacts communities of color across 52 US cities
Low-income and minority neighborhoods in U.S. exposed to 28% more nitrogen dioxide pollution, study finds
Peer-Reviewed PublicationIMAGE: ACROSS 52 U.S. CITIES, LARGE DISCREPANCIES IN EXPOSURE TO NO2 POLLUTION EXIST BETWEEN LOW-INCOME COMMUNITIES OF COLOR AND HIGH-INCOME WHITE COMMUNITIES. THE INEQUALITY IS DRIVEN PRIMARILY BY PROXIMITY TO ROADWAYS WITH HEAVY DIESEL TRUCK TRAFFIC, SAYS A NEW STUDY IN GEOPHYSICAL RESEARCH LETTERS. view more
CREDIT: CREDIT: DEMETILLO ET AL. (2021)/GEOPHYSICAL RESEARCH LETTERS
WASHINGTON—In urban areas across the U.S., low-income neighborhoods and communities of color experience an average of 28% more nitrogen dioxide (NO2) pollution than higher-income and majority-white neighborhoods. The disparity is driven primarily by proximity to trucking routes on major roadways, where diesel trucks are emitters of NO2 and other air pollutants.
Nitrogen dioxide is a common air pollutant that can cause a range of health problems, such as chronic respiratory illness and asthma. But it can be difficult to trace.
A new study used high-resolution air pollution data measured with satellites to track NO2 for nearly two years in major cities across the U.S. The researchers then paired the pollution data with both demographic data and metrics that analyze the degree of racial segregation in a community.
Cities with bigger populations tended to have larger disparities in NO2 pollution between low-income neighborhoods of color and high-income white neighborhoods, according to the study. Phoenix, Los Angeles and Newark, N.J., have the highest NO2 inequalities, all with a discrepancy in NO2 exposure of over 40%.
Both commuter traffic and heavy-duty trucks contribute NO2 and other pollutants, but diesel trucks are the dominant source, contributing on average up to half of a city’s NO2 despite being at most 5% of traffic. Because diesel trucks also emit other harmful gases and particulates, changes in NO2 are also thought to reflect exposure to other pollutants as well.
The findings are detailed in the AGU journal Geophysical Research Letters, which publishes high-impact, short-format reports with immediate implications spanning all Earth and space sciences.
“One of the novel things we looked at was the integration of segregation metrics and air quality. Previously, we had been limited in our ability to address air pollution inequality, but with improvements in satellite resolution we are now able to get spatially and temporally continuous data at finer resolutions within cities,” said Angelique Demetillo, an atmospheric chemist at the University of Virginia and lead author of the study.
Measuring pollutants like NO2 is difficult to do at a scale that’s useful to local policymakers. While previous studies have shown disparities in air quality, the new findings offer near-daily pollution data at small scales, providing important quantitative information policymakers can use to guide zoning and public health and that can reflect the lived experience of community members.
The new study found a 60% drop in heavy trucking on weekends results in a 40% decrease in air pollution inequality. That can point policymakers to a clear emissions-reducing target.
“In terms of environmental justice, one of the things we have lacked is these observations across an entire city that also have temporal variability that we can use to understand the sources [of pollution],” said Sally Pusede, an atmospheric chemist at the University of Virginia who co-authored the study.
“We have these new data and methodologies that continue to show us what we already know through experience, but in the U.S., it’s [quantitative] data that informs policy,” said Regan Patterson, a transportation and public health expert at the Congressional Black Caucus Foundation.
Bigger city, bigger disparity
Transitioning to electric heavy-duty trucks could be one way of reducing pollution exposure in neighborhoods close to highways. California already has a mandate of doing this by 2045. But, Pusede pointed out, while emissions from diesel trucks are the biggest driver of exposure inequality, other pollution sources contribute to the problem. “Even if we eliminated emissions from trucking, we would still see inequalities present because there are other sources of inequality.”
Discrepancies in exposure to pollution between communities of color and white communities are well-documented. They often stem from zoning practices that result in communities of color forming in less desirable areas or infrastructure like highways being built in close proximity to — or through — a neighborhood.
Patterson said over the long term, transformative changes are needed to truly begin to remove NO2 pollution disparity. “How do you rectify the inequities that have literally been built into the environment, where certain groups are more likely to be adjacent to major roadways?” she asked.
Both Patterson and Pusede referenced a bill in the new infrastructure package aimed at physically reconnecting communities by removing freeways as a necessary step toward equalizing air quality. More immediately, Demetillo hoped her study and studies like it will help put air-quality information into the hands of community members.
“I see this as just the beginning. There are a lot of potential end-user applications, like people in different cities using this information to help them make decisions about how to go about their day. For policymakers, this could be a new way to plan mitigation solutions or to monitor how well those mitigation strategies are playing out,” Demetillo said.
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Notes for Journalists:
This research study is published with open access and is freely available. Download a PDF copy of the paper here. Neither the paper nor this press release is under embargo.
Paper title:
“Space-Based Observational Constraints on NO2 Air Pollution Inequality From Diesel Traffic in Major US Cities”
Authors:
- Mary Angelique G. Demetillo, Sally E. Pusede (corresponding author), Department of Environmental Sciences, University of Virginia, Charlottesville, VA, USA
- Colin Harkins, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA, and NOAA Chemical Sciences Laboratory, Boulder, CO, USA
- Brian C. McDonald, NOAA Chemical Sciences Laboratory, Boulder, CO, USA
- Philip S. Chodrow, Department of Mathematics, University of California Los Angeles, Los Angeles, CA, USA
- Kang Sun, Department of Civil, Structural and Environmental Engineering and Research and Education in eNergy, Environment and Water (RENEW) Institute, University at Buffalo, Buffalo, NY, USA
JOURNAL
Geophysical Research Letters
DOI
ARTICLE TITLE
Space-Based Observational Constraints on NO2 Air Pollution Inequality From Diesel Traffic in Major US Cities
ARTICLE PUBLICATION DATE
25-Aug-2021
Years of exposure to air pollution and road traffic noise may raise heart failure risk
Journal of the American Heart Association Report
Peer-Reviewed PublicationDALLAS, Oct. 6, 2021 — Exposure to air pollution and road traffic noise over the course of many years may be associated with an increased risk of developing heart failure, and the correlation appears to be even greater in people who are former smokers or have high blood pressure, according to new research published today in the Journal of the American Heart Association, an open access journal of the American Heart Association.
“We found that long-term exposure to specific air pollutants and road traffic noise increased the risk of incident heart failure, especially for former smokers or people with hypertension, so preventive and educational measures are necessary,” said Youn-Hee Lim, Ph.D., lead author of the study and assistant professor in the section of environmental health within the department of public health at the University of Copenhagen in Copenhagen, Denmark. “To minimize the impact of these exposures, broad public tactics such as emissions control measures should be implemented. Strategies like smoking cessation and blood pressure control must be encouraged to help reduce individual risk.”
This analysis examined the impact of long-term environmental exposure, specifically from air pollution and road traffic noise, on the development of heart failure in a group of female nurses in Denmark over a 15-to-20-year period.
Researchers collected data from a prospective study of over 22,000 members of the all-female Danish Nurse Cohort study. The women were 44 years of age and older at study enrollment and living in Denmark. Participants were recruited in 1993 or 1999, and when they enrolled, each woman completed a comprehensive questionnaire on body mass index, lifestyle factors (smoking, alcohol consumption, physical activity and dietary habits), pre-existing health conditions, reproductive health and working conditions. Information on heart failure diagnoses was gathered throughout the 20-year follow by linking study participants to the Danish National Patient Register, which includes records on all health care provided at hospitals in Denmark. Patient data was collected through December 31, 2014.
The study group lived in rural, urban and suburban areas throughout Denmark. To best measure individual exposure to air pollution and road traffic noise, researchers maintained records of each individual’s residential addresses, including any moves to new residences from 1970 and 2014. To determine levels of air pollution, the yearly average concentrations of two components, fine particulate matter (PM2.5) and nitrogen dioxide (NO2), were measured using a Danish air pollution modeling system. Road traffic noise levels within a three-kilometer radius from the participants’ residential addresses were estimated using a validated model system called Nord2000 and measured in decibels (dB), the standard unit for the intensity of sound.
The analysis of various pollutants and their effects on incident heart failure found:
- For every 5.1 µg/m3 increase in fine particulate matter exposure over three years, the risk of incident heart failure increased by 17%;
- For every 8.6 µg/m3 increase in NO2 exposure over three years, the risk of incident heart failure increased by 10%;
- For every 9.3 dB increase in road traffic noise exposure over three years, the risk of incident heart failure increased by 12%; and,
- Increased exposure to fine particulate matter and status as a former smoker were associated with a 72% increased risk of incident heart failure.
“We were surprised by how two environmental factors – air pollution and road traffic noise – interacted,” Lim said. “Air pollution was a stronger contributor to heart failure incidence compared to road traffic noise; however, the women exposed to both high levels of air pollution and road traffic noise showed the highest increase in heart failure risk. In addition, about 12% of the total study participants had hypertension at enrollment of the study. However, 30% of the nurses with heart failure incidence had a previous history of hypertension, and they were the most susceptible population to air pollution exposure.”
The study has several limitations. Researchers did not have information on additional variables that may have affected the results of the analysis, such as measures for each individual’s exposure to indoor air pollution or occupational noise; the amount of time spent outdoors; glass thickness of the windows of their home, which may influence noise pollution levels; if they had a hearing impairment; or individual socioeconomic status. Additionally, almost one-fourth of the original participants in the Danish Nurse Cohort were excluded from the final analysis because information was missing at the beginning of the study or at the study’s completion, so selection bias may be a contributing factor. The researchers also note that since they investigated Danish female nurses’ exposure levels and health outcomes, a generalization of the results to men or other populations warrants caution.
Previous research has shown an association between air pollution and cardiovascular disease, and the American Heart Association detailed a collection of research on the risks of pollution in a scientific statement in 2004, with additional updated findings added in 2010. In 2020 the American Heart Association American Heart Association published a scientific statement and policy guidance to address the implications of air pollution amid the COVID-19 pandemic and beyond. The policy statement discusses policy guidance at the local, state and federal levels to improve the health of our communities. Short-term exposure to high levels of some air pollutants has also been linked to heart failure.
Co-authors are Jeanette Therming Jørgensen, M.Sc., Ph.D.; Rina So, Ph.D. student; Tom Cole-Hunter, Ph.D.; Amar Mehta, Sc.D.; Heresh Amini, Ph.D.; Elvira Bräuner, Ph.D.; Rudi Westendorp, M.D., Ph.D.; Shuo Liu, M.P.H.; Laust Mortensen, Ph.D.; Barbara Hoffmann; Steffen Loft, D.M.Sc.; Matthias Ketzel, Ph.D.; Ole Hertel, D.Sc.; Jørgen Brandt, Ph.D.; Steen Solvang Jensen, Ph.D.; Claus Backalarz; Mette K. Simonsen, M.Sc.; Nebojsa Tasic; Matija Maric; and Zorana J. Andersen, Ph.D. Authors’ disclosures are in the manuscript.
The study was funded by the Danish Council for Independent Research, the Region Zealand Fund and the Novo Nordisk Foundation Challenge Programme.
Additional Resources:
- Multimedia is available on the right column of release link:
- After Oct. 6, view the manuscript online.
- What is Heart Failure?
- Air Pollution and Heart Disease, Stroke
- Particulate Matter Air Pollution and Cardiovascular Disease
- Follow AHA/ASA news on Twitter @HeartNews
- Follow news from the Journal of the American Heart Association @JAHA_AHA
Statements and conclusions of studies published in the American Heart Association’s scientific journals are solely those of the study authors and do not necessarily reflect the Association’s policy or position. The Association makes no representation or guarantee as to their accuracy or reliability. The Association receives funding primarily from individuals; foundations and corporations (including pharmaceutical, device manufacturers and other companies) also make donations and fund specific Association programs and events. The Association has strict policies to prevent these relationships from influencing the science content. Revenues from pharmaceutical and biotech companies, device manufacturers and health insurance providers and the Association’s overall financial information are available here.
About the American Heart Association
The American Heart Association is a relentless force for a world of longer, healthier lives. We are dedicated to ensuring equitable health in all communities. Through collaboration with numerous organizations, and powered by millions of volunteers, we fund innovative research, advocate for the public’s health and share lifesaving resources. The Dallas-based organization has been a leading source of health information for nearly a century. Connect with us on heart.org, Facebook, Twitter or by calling 1-800-AHA-USA1.
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ARTICLE TITLE
Long-Term Exposure to Air Pollution, Road Traffic Noise, and Heart Failure Incidence: The Danish Nurse Cohort
ARTICLE PUBLICATION DATE
6-Oct-2021
Air pollution caused 1.1 million death across Africa in 2019, new study finds
Air pollution bears economic costs and hinders intellectual development of Africa’s children, most far-reaching assessment of air pollution in Africa finds
Peer-Reviewed PublicationChestnut Hill, Mass. (10/7/2021) -- Air pollution was responsible for 1.1 million deaths across Africa in 2019, with household air pollution -- driven largely by indoor cookstoves -- accounting for 700,000 fatalities, while increased outdoor air pollution claimed 400,000 lives, a team of researchers led by Boston College and the UN Environment Programme report in the latest edition of the journal The Lancet Planetary Health.
Furthermore, air pollution is costing African countries billions in gross domestic product and can be correlated to a devastating loss in the intellectual development of Africa’s children, the researchers found.
In the first continent-wide examination of the far-reaching impacts of air pollution in Africa, the international team found that while deaths from household air pollution have declined slightly, deaths caused by outdoor, or ambient, air pollution are on the rise, said Boston College Professor of Biology Philip Landrigan, MD, who led the project with United Nations Environment Programme Chief Environmental Economist Pushpam Kumar.
“The most disturbing finding was the increase in deaths from ambient air pollution,” said Landrigan, director of Boston College’s Global Observatory on Pollution and Health. “While this increase is still modest, it threatens to increase exponentially as African cities grow in the next two to three decades and the continent develops economically.”
The African continent is undergoing a massive transformation, the co-authors note. Africa’s population is on track to more than triple in this century, from 1.3 billion in 2020 to 4.3 billion by 2100. Cities are expanding, economies are growing, and life expectancy has almost doubled. Fossil fuel combustion has driven an increase in outdoor air pollution that in 2019 killed 29.15 people per 100,000 population, an increase from 26.13 deaths per 100,000 in 1990, according to the report, which is available at https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(21)00201-1/fulltext.
Indoor and outdoor sources combine to make air pollution the second largest cause of death in Africa, claiming more lives than tobacco, alcohol, motor vehicle accidents, and drug abuse. Only AIDS causes more deaths. Africa is part of a global toll taken by air pollution, which killed an estimated 6.7 million people worldwide in 2017, the paper notes.
“Air pollution in Africa has major negative impacts on health, human capital and the economy,” the co-authors conclude. “These impacts are growing in magnitude as countries develop.”
Examining the toll on the developing brains of children, the researchers calculate that air pollution exposure to infants and young children resulted in the loss of 1.96 billion IQ points across the continent.
The team studied trends in air pollution in Africa to determine impacts on human health and economic development in 54 African countries. The team devoted special attention to three rapidly developing Sub-Saharan countries - Ethiopia, Ghana and Rwanda.
“We focused on these three countries because they are all at somewhat different points in their economic development, and we reasoned that comparing air pollution patterns among them would give us a good indicator of future trends,” Landrigan said.
Within these three countries, the upward trend in outdoor air pollution is most clearly evident in Ghana, the most economically advanced of the countries, and beginning to be seen in Ethiopia and Rwanda, Landrigan said.
“Experience from other countries suggests that the increases in AAP appearing in Africa today could be the harbinger of a looming problem,” according to the report. “In the absence of visionary leadership and intentional intervention, AAP could become a much larger cause of disease and premature death than at present and could pose a major threat to economic development.”
In addition to the toll on human health, air pollution imposes economic costs, the study found. Economic output lost to air-pollution-related disease was $3.0 billion in Ethiopia, or 1.16 percent of the nation’s gross domestic product; $1.6 billion in Ghana (0.95 percent of GDP), and $349 million in Rwanda (1.19 percent of GDP).
“Investment in pollution control besides climate and biodiversity has significant return than usually construed," said UNEP's Kumar. "This study from three diverse countries of Africa demonstrates that managing pollution favorably impacts human capital and helps lay the foundation for sustainable recovery in the post-pandemic era.”
The study recommends governments make air pollution prevention and control national priorities and create sustainable funding to support those priorities. Specific recommendations include:
- Invest in clean renewable energy, in particular taking advantage of solar and wind power resources and reducing reliance on coal, oil, and gas.
- Reduce road traffic and traffic-related pollution by raising fuel taxes and parking fees, levying congestion charges, creating vehicle-free zones and cycle paths, and improving public transportation.
- Regulate the open burning of waste by households and firms and place restrictions on agricultural burning, including burning forest to convert to agricultural land as well as crop residue burning.
- Undertake systemic reforms to identify, control, and track sources of indoor and outdoor air pollution and sponsor research to further assess the impact on public health.
“We encourage Africa's leaders to take advantage of the fact that their countries are still relatively early in their economic development and to transition rapidly to wind and solar energy, thus avoiding entrapment in fossil-fuel-based economies,” said Landrigan. “We argue that African countries are in a unique position to leapfrog over mistakes made elsewhere and to achieve prosperity without pollution.”
“Air pollution in Africa threatens economic development and future growth, but can be avoided by wise leaders who transition rapidly to wind and solar energy and avoid entrapment by coal, gas and oil,” Landrigan said.
In addition to Landrigan and Kumar, co-authors of the report include Boston College researchers Samantha Fisher, senior data scientist at the Global Observatory on Pollution and Health, and Gabriella Taghian; David C. Bellinger, of Boston Children’s Hospital/Harvard Medical School; Maureen L. Cropper, of the University of Maryland; Agnes Binagwaho, MD, vice chancellor of the University of Global Health Equity, Rwanda; Juliette Biao Koudenoukpo, United Nations Environment Programme; and Yongjoon Park, of the University of Massachusetts Amherst.
JOURNAL
The Lancet Planetary Health
METHOD OF RESEARCH
Data/statistical analysis
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Air Pollution and Development in Africa: Impacts on Health, the Economy, and Human Capital
ARTICLE PUBLICATION DATE
7-Oct-2021
Long-term exposure to permissible concentrations of air pollution linked with increased mortality risk
Boston, MA – Exposure to low concentrations of air pollution, even at levels permitted under federal regulations, may be causing tens of thousands of early deaths each year among elderly people and other vulnerable groups in the U.S., according to a large national study from Harvard T.H. Chan School of Public Health.
The study will be published October 7, 2021, in The Lancet Planetary Health.
“We found that among elderly patients enrolled in Medicare, small increases in long-term exposure to both particle and gaseous air pollutants increased the risk of death, even at levels deemed safe by current regulations,” said lead study author Mahdieh Danesh Yazdi, a postdoctoral fellow in Harvard Chan School’s Department of Environmental Health. “Our findings suggest that current air pollution limits are not adequate to protect the health of vulnerable groups.”
Previous studies have suggested that people exposed to air pollution concentrations that are lower than those permitted by the U.S. Environmental Protection Agency may still have an increased risk of illness and mortality. But most earlier studies didn’t focus on individuals who were continually exposed to lower concentrations of pollutants during the study period, as the new study does. Researchers also used a robust causal modeling technique and a large dataset for their analysis that gave them enough power to detect links between air pollution and mortality in demographic and socioeconomic subgroups.
The analysis included data on millions of Medicare enrollees from 2000 to 2016. The researchers predicted people’s exposure levels by using satellite-based measurements, land-use data, meteorological data, and chemical-transport models to generate daily air pollution predictions as well as annual averages of exposure levels across the U.S. Participants were assigned exposures based on their residential postal codes. The researchers adjusted for factors such as age, sex, race, education level, and smoking history.
The study looked at the effects of three different types of pollutants, including fine particulate matter, or PM2.5—particulates with a diameter of less than 2.5 micrograms per cubic meter of air (μg/m3)—nitrogen dioxide (NO2), and summer ozone (O3). The researchers limited their dataset to individuals who were exposed to air pollution concentrations below the annual maximums recommended by the EPA. For PM2.5, the threshold is 12 μg/m3; for NO2, it’s 53 parts per billion (ppb). There is no regulation regarding long-term exposure for O3, so the researchers chose 50 ppb as an upper exposure limit for the purposes of the study.
All of the studied pollutants increased the mortality risk among the participants. Thousands of deaths could be attributed to even small increases in annual air pollution concentrations, according to the researchers.
Each 1 μg/m3 increase in annual PM2.5 concentrations increased the absolute annual risk of death by 0.073%. Each 1 ppb increase in annual NO2 concentrations increased the annual risk of death by 0.003%, and each 1 ppb increase in summer O3 concentrations increased the annual risk of death by 0.081%. These increases translated to approximately 11,540 deaths attributable to PM2.5, 1,176 deaths attributable to NO2, and 15,115 deaths attributable to O3 per year for each unit increase in pollution concentrations.
Men were at greater risk of death from PM2.5 and O3, and people who identified as Black had a higher risk of death caused by NO2 and O3. The study also found an increased risk of death for people living in lower-income areas, pointing to disparities in the adverse effects of air pollution.
The results suggest that a 2020 EPA decision not to tighten standards for ambient PM2.5 “was unjustified,” the researchers wrote. They listed interventions that could reduce air pollutants, such as stricter controls on industry and fossil-fuel electric-generating units, larger and more efficient catalysts on automobiles, city planning to promote active transport, and improved public transit.
“Our finding that people living in lower income areas are more susceptible to the harmful effects of air pollution means they are suffering a double whammy—more exposure, and greater risk from that exposure,” said Joel Schwartz, professor of environmental epidemiology and senior author of the study. “The Clean Air Act requires the EPA to protect sensitive populations with an adequate margin of safety. It is time for it to do so.”
Other Harvard Chan School authors of the study included Yan Wang, Qian Di, Weeberb Requia, Yaguang Wei, Liuhua Shi, Matthew Sabath, Francesca Dominici, Brent Coull, John Evans, and Petros Koutrakis.
Funding for the study came from U.S. Environmental Protection Agency grant RD-835872, from National Institute of Environmental Health Sciences P30-ES000002, and Health Effects Institute grant 4953-RFA14-3/16-4.
“Long-term Effect of Exposure to Lower Concentrations of Air Pollution on Mortality among Medicare Participants and Vulnerable Subgroups,” Mahdieh Danesh Yazdi, Yan Wang, Qian Di, Weeberb J. Requia, Yaguang Wei, Liuhua Shi, Matthew Benjamin Sabath, Francesca Dominici, Brent Coull, John S. Evans, Petros Koutrakis, and Joel D. Schwartz, The Lancet Planetary Health, October 7, 2021, doi: 10.1016/S2542-5196(21)00204-7
JOURNAL
The Lancet Planetary Health
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
People
ARTICLE TITLE
Long-term Effect of Exposure to Lower Concentrations of Air Pollution on Mortality among Medicare Participants and Vulnerable Subgroups
ARTICLE PUBLICATION DATE
7-Oct-2021
