Chronic exposure to air pollution may increase risk of cardiovascular hospitalization among seniors
Key points:
- Chronic exposure to fine particulate air pollutants (PM2.5) may increase seniors’ risk of cardiovascular hospitalization, with disproportionate impacts on residents of socioeconomically deprived neighborhoods.
- The findings suggest that to protect heart health, there is no safe threshold for chronic PM2.5 exposure, and that the EPA’s newly updated standard for the U.S.’s annual average PM2.5 level isn’t low enough to reduce the burden of cardiovascular disease or protect public health overall.
Boston, MA—Chronic exposure to fine particulate air pollutants (PM2.5) may increase seniors’ risk of hospitalization for a variety of cardiovascular conditions, according to a new study led by Harvard T.H. Chan School of Public Health.
“The timing of our study couldn’t be more critical, and its implications are profound,” said lead author Yaguang Wei, research associate in the Department of Environmental Health. “Our findings quantify the benefits of implementing stricter air pollution control policies—even stricter than the Environmental Protection Agency’s new standards, which are considerably higher than the 5 micrograms per cubic meter standard set by the World Health Organization.” On Feb. 7, the Environmental Protection Agency (EPA) announced its updated National Ambient Air Quality Standards, lowering the country’s permissible average annual PM2.5 level from 12 micrograms per cubic meter (μg/m3) to 9 μg/m3.
The study will be published online in The BMJ on February 21, 2024.
The researchers examined the hospital records and PM2.5 exposure levels of nearly 60 million Medicare beneficiaries, ages 65 and higher, between 2000 and 2016. Drawing from a variety of air pollution data sources, they developed a predictive map of PM2.5 levels across the contiguous U.S. and linked it to beneficiaries’ residential ZIP codes. The researchers followed each beneficiary each year until their first hospitalization for any of seven major subtypes of cardiovascular disease (CVD): ischemic heart disease, cerebrovascular disease, heart failure, cardiomyopathy, arrhythmia, and thoracic and abdominal aortic aneurysms. They also looked at the risk of first admission for a composite of the CVD subtypes.
The study found that three-year average exposure to PM2.5 was associated with increased risk of a first hospital admission for all cardiovascular conditions, particularly ischemic heart disease, cerebrovascular disease, heart failure, and arrythmia. For composite CVD, the study found that when chronic exposure to PM2.5 was between 7 and 8 μg/m3, representative of the current national average level, on average the risk of hospitalization for cardiovascular disease in seniors was 3.04% each year. For comparison, when chronic exposure to PM2.5 met the WHO guideline of below 5 μg/m3, on average the risk of hospitalization for CVD was 2.59% each year. Based on these estimates, researchers calculated that lowering annual average PM2.5 levels from 7-8 μg/m3 to below 5 μg/m3 could decrease overall cardiovascular hospitalizations by 15%.
Even given this improvement, the findings suggest that to protect overall cardiovascular health, there is no safe threshold for chronic exposure to PM2.5, say the researchers. They also observed that the health risks of chronic PM2.5 exposure remain substantial for at least three years, and that they disproportionately impact people with lower educational levels, limited access to health care, and who live in socioeconomically deprived neighborhoods.
“Stronger efforts are urgently needed to improve air quality and thereby alleviate the burden of cardiovascular disease—a leading cause of death and a major contributor to health care costs,” said senior author Joel Schwartz, professor of environmental epidemiology. “Our findings indicate that the EPA’s newly updated PM2.5 standard is clearly insufficient for the protection of public health.”
Other Harvard Chan authors included Yijing Feng, Mahdieh Danesh Yazdi, Edgar Castro, Alexandra Shtein, Xinye Qiu, Adjani Peralta, Brent Coull, and Francesca Dominici.
Funding for the study came from the National Institutes of Health (grants R01ES032418, R01MD012769, R01ES028033, R01AG060232, R01ES030616, R01AG066793, R01MD016054, P30ES000002) and the Alfred P. Sloan Foundation (grant G-2020-13946).
“Exposure-response associations between chronic exposure to fine particulate matter and risks of hospital admission for major cardiovascular diseases: population based cohort study,” Yaguang Wei, Yijing Feng, Mahdieh Danesh Yazdi, Kanhua Yin, Edgar Castro, Alexandra Shtein, Xinye Qiu, Adjani A. Peralta, Brent A. Coull, Francesca Dominici, Joel D. Schwartz, The BMJ, online February 21, 2024, doi: 10.1136/ bmj-2023-076939
Visit the Harvard Chan School website for the latest news, press releases, and multimedia offerings.
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Harvard T.H. Chan School of Public Health brings together dedicated experts from many disciplines to educate new generations of global health leaders and produce powerful ideas that improve the lives and health of people everywhere. As a community of leading scientists, educators, and students, we work together to take innovative ideas from the laboratory to people’s lives—not only making scientific breakthroughs, but also working to change individual behaviors, public policies, and health care practices. Each year, more than 400 faculty members at Harvard Chan School teach 1,000-plus full-time students from around the world and train thousands more through online and executive education courses. Founded in 1913 as the Harvard-MIT School of Health Officers, the School is recognized as America’s oldest professional training program in public health.
JOURNAL
BMJ
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Exposure-response associations between chronic exposure to fine particulate matter and risks of hospital admission for major cardiovascular diseases: population based cohort study
ARTICLE PUBLICATION DATE
21-Feb-2024
Air pollution hides increases in rainfall
For much of the last century, the drying effect of aerosols has masked increases in rainfall from greenhouse gases – but as aerosol emissions diminish, average and extreme rains may ramp up.
IMAGE:
THESE MAPS SHOW HOW AEROSOL AND GREENHOUSE GAS EMISSIONS INFLUENCE EXTREME RAINFALL ACROSS THE SEASONS. GREEN INDICATES AN INCREASE IN RAIN, WHILE BROWN MEANS A DECREASE. GREENHOUSE GASES LARGELY INCREASE RAINFALL ACROSS ALL THE SEASONS, BUT AEROSOLS WORK IN TWO WAYS: THE SLOW IMPACT GENERALLY CAUSES DRYING ACROSS THE SEASONS, WHILE THE FAST IMPACT CAUSES MORE DRYING IN THE WINTER AND SPRING, AND MORE RAIN IN THE SUMMER AND FALL.
view moreCREDIT: BERKELEY LAB
We know that greenhouse gas emissions like carbon dioxide should increase rainfall. The emissions heat the atmosphere, causing a one-two punch: warmer oceans make it easier for water to evaporate, and warmer air can hold more water vapor, meaning more moisture is available to fall as rain. But for much of the 20th century, that increase in precipitation didn’t clearly show up in the data.
A new study led by researchers at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) finds that the expected increase in rain has been largely offset by the drying effect of aerosols – emissions like sulfur dioxide that are produced by burning fossil fuels, and commonly thought of as air pollution or smog. The research is published today in the journal Nature Communications.
“This is the first time that we can really understand what’s causing extreme rainfall to change within the continental U.S.,” said Mark Risser, a research scientist at Berkeley Lab and one of the lead authors for the study. He noted that until the 1970s, the expected increases to extreme rainfall were offset by aerosols. But the Clean Air Act caused a drastic reduction in air pollution in the United States. “The aerosol masking was turned off quite suddenly. That means rainfall might ramp up much more quickly than we would have otherwise predicted.”
Traditional climate models have struggled to confidently predict the human impact on rainfall at scales smaller than a continent – and that regional level is precisely where most climate change adaptations and mitigations take place. By using a new method and relying heavily on measurements from rain gauges from 1900 to 2020, researchers were able to more robustly determine how human activities have influenced rainfall in the United States.
"Prior to our study, the Intergovernmental Panel on Climate Change [IPCC] had concluded that the evidence was mixed and inconclusive for changes in U.S. precipitation due to global warming,” said Bill Collins, associate laboratory director for the Earth and Environmental Sciences Area at Berkeley Lab and co-lead author on the study. “We have now provided conclusive evidence for higher rainfall and also helped explain why past studies assessed by the IPCC reached conflicting conclusions."
Specifically, the study isolates how greenhouse gas and aerosol emissions affect both average and extreme rainfall. Researchers confirmed that increased greenhouse gas emissions, which quickly disperse over the whole planet, cause an increase in rainfall. The impact from aerosols is more nuanced. Over the long term, aerosols cool the planet, which causes a drying effect. But they also have a faster, more local response. That fast impact depends on the season, with aerosols generally reducing rainfall in the winter and spring, and amplifying it in summer and fall over much of the United States.
“The seasonality piece is really important,” Risser said. “For rainfall, the nature of climate change depends on what season you’re talking about, since different kinds of weather systems create precipitation in different parts of the year.”
Some of the conflicting studies looking at precipitation trends of the last century can be explained by how the effect of aerosols offsets the effect of greenhouse gases, and how models and simulations factor in these two driving forces. The researchers noted that tracking aerosols and incorporating them more fully into models and simulations will be important for improving the predictions used for infrastructure design and water resource management.
The United States has already seen examples of recent increases in extreme precipitation, with several intense, record-setting storms in the past few years.
"Thanks to improvements in air quality, the aerosols that shielded us from the worst effects of global warming are declining worldwide,” Collins said. “Our work shows that the increases in extreme precipitation driven by elevated ocean temperatures will become increasingly obvious during this decade."
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Lawrence Berkeley National Laboratory (Berkeley Lab) is committed to delivering solutions for humankind through research in clean energy, a healthy planet, and discovery science. Founded in 1931 on the belief that the biggest problems are best addressed by teams, Berkeley Lab and its scientists have been recognized with 16 Nobel Prizes. Researchers from around the world rely on the lab’s world-class scientific facilities for their own pioneering research. Berkeley Lab is a multiprogram national laboratory managed by the University of California for the U.S. Department of Energy’s Office of Science.
DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science.
JOURNAL
Nature Communications
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