Individuals who suffer from a common heart ailment and also live in areas of Allegheny County where air pollution is the worst are significantly more likely to have a stroke, according to a new study.
Researchers at the UPMC Heart and Vascular Institute and the University of Pittsburgh School of Medicine identified and followed 31,400 county residents from 2007 through 2017 who had atrial fibrillation, or Afib, and found those living in high pollution neighborhoods had a 20% higher stroke risk than those living where the air was cleanest.
Afib is a heart rhythm disorder that affects more than 2.7 million Americans.
Recently published by the American Medical Association’s JAMA Network Open, an online peer-reviewed journal, the study is the largest to consider neighborhood-specific pollution data and, according to researchers, emphasizes the importance of air pollution alerts that can help people adjust activity levels during high pollution days.
“We measured pollution exposure at people’s doorsteps ... then determined their annual exposure to particulate matter. This approach and the sample size make our study particularly powerful,” said Dr. Jared W. Magnani, a UPMC cardiologist and associate professor of medicine at Pitt, who was one of the lead researchers on the study.
He said people with Afib are already at five times the risk of stroke, so the additional risk from breathing polluted air is a concern.
“We can use this information to guide our patients by advising them to limit exposure to pollution,” Dr. Magnani said. “For example, we can notify those with atrial fibrillation to avoid being outside on days with unhealthy air quality, which may reduce their risk of stroke.”
All individuals in the study were seen at the University of Pittsburgh Medical Center and had an Afib diagnosis. Follow-up contacts were made through 2017.
The Pittsburgh metropolitan region, including Allegheny County, is ranked as eighth worst for annual particle pollution among 204 U.S. metropolitan regions by the American Lung Association in its 2020 “State of the Air” report.
Dr. Magnani said researchers found stroke risk steadily increased with higher daily exposure to fine airborne particulate matter, known as PM2.5, which can be breathed into the lungs and enters the bloodstream where it can trigger heart events like a stroke.
For purposes of the study, high annual exposure to PM2.5 averaged between 11.1 and 15.7 micrograms per cubic meter of air, and low exposure was in the range of 9.1 to 10.1 micrograms per cubic meter. The federal annual PM2.5 standard is 12 micrograms per cubic meter of air.
But Jane Clougherty, a co-principal investigator on the study and associate professor at the Drexel University Dornsife School of Public Health, said the low range of pollution shouldn’t be thought of as “safe.”
“The key finding of this study was that stroke risk really consistently increased across [the range of exposures],” said Ms. Clougherty, who holds a doctorate in environmental health from the Harvard School of Public Health. “Higher PM2.5 was consistently associated with higher stroke risk in this susceptible population.”
According to the Allegheny County Health Department, the county is measuring in nonattainment for annual PM2.5, with the Liberty air quality monitor downwind from U.S. Steel’s Clairton Coke Works in the Monongahela River valley south of Pittsburgh showing an annual average in 2019 of 12.2 micrograms per cubic meter (ug/m3) and a three-year average of 12.4 ug/m3.
The other eight PM2.5 monitors in the county all are meeting the federal standard with annual averages of between 6.8 (North Park) and 10.8 ug/m3 (Parkway East) for last year, part of a downward trend.
In a response to questions, Aaron Aupperlee, a Health Department spokesman, said the county also is measuring in nonattainment for sulfur dioxide emissions but “expects the region will measure in attainment of both PM2.5 and sulfur dioxide by the end of 2021.”
Ms. Clougherty said the vast majority of PM2.5 exposures to individuals in the study group were below the federal health standard, but a consistent link between exposure and stroke risk was still clear.
“ACHD is correct that air quality is consistently improving in the Pittsburgh area, which is great for health,” Ms. Clougherty said. “And, based on these results and other studies, we would encourage further efforts to continue to reduce exposures below current guidelines.”
Ms. Clougherty and Dr. Magnani said the study’s findings are applicable nationwide, given that fine particle pollution is a problem in many metropolitan areas and federal deregulation is reducing standards and limiting controls.
“There certainly may be generalizable findings here, in that many US cities have high PM exposures, which may well be associated with higher risk of stroke among Afib patients in those settings,” Ms. Clougherty said.
She said a separate study in New York City by her lab has identified a higher stroke risk due to same day exposures to elevated levels of both PM2.5 and nitrogen oxides, an indirect greenhouse gas that reacts with sunlight and other chemicals to form unhealthy smog.
Dr. Magnani said the study’s findings, while based on Allegheny County pollution exposures, have a national scope.
“We can expect increased health complications with the catastrophic fires on the West coast, or with increasing deregulation of industry,” Dr. Magnani said. “These events will have large health effects and implications for individual health in the years to come. Our study adds to significant data that supports the contribution of pollution to adverse health outcomes.”
He said future research could explore how individual factors like physical activity, diet, health care access and medication could mitigate stroke risk for people with Afib.
The Pitt-UPMC study also looked at demographic and socioeconomic data and found that exposure to fine airborne particle pollution was 50% higher among Black residents than white and 30% higher for those living in poverty.
“This important study of risk of stroke in Allegheny County not only reminds us of the impact that air pollution has on the health of our residents but also of the health and income disparities within our county,” said LuAnn Brink, the county Health Department’s chief epidemiologist.
She said the study findings that show Black residents make up 20% of the population in the county’s most polluted areas but only 1% in the least polluted areas raises an environmental justice issue.
“Income was also vastly different, with a median income of over $78,000 among those least exposed to air pollution compared to just over $33,000 for those most exposed,” Ms. Brink said. “We at ACHD are committed to further exploring these social determinants of health, their interrelationship, and finding solutions to improve the health of all our residents, particularly the most vulnerable.”
Dr. Magnani said it’s well known that racial and ethnic minorities suffer disproportionate health impacts from environmental exposures, and those exposures are amplified by social and economic factors.
“We as a community and a society,” he said, “need to confront the racial segregation that gives Black people greater industrial exposure and in turn a higher level of pollution at their doorstep.”
Don Hopey: dhopey@post-gazette.com or 412-263-1983. Twitter: @donhopey.
First Published: September 24, 2020, 9:30 a.m.
