Researchers at the Boston, Mass-based Beth Israel Deaconess Medical Center report that air pollution, even at the moderate level considered generally safe by federal regulations, may increase the risk of stroke by 34%. The researchers conducted a recent study reportedly encompassed more than 1,700 stroke patients in the Boston, Mass, area. The 10-year study suggested a link between exposure to ambient fine particulate matter, generally from vehicle traffic, on days when the US Environmental Protection Agency (EPA)’s air quality index for particulate matter was yellow instead of green, and a higher risk of ischemic strokes.

Researchers note that the study focused on particles with a diameter of 2.5 millionths of a meter, or PM2.5. The particles can yield from multiple sources, including power plants, factories, vehicles, and burning wood, a recent news release explains. Researchers add that the particles have the ability to travel deep into the lungs and are linked in other studies to an increased number of hospital visits for cardiovascular diseases. 

Murray A. Mittleman, MD, DrPH, physician in the CardioVascular Institute at Beth Israel Deaconess Medical Center, and associate professor or medicine at Harvard Medical School, served as senior study author. Mittleman points out that the parallel between increased stroke risk and the inhalation of particulates, such as those associated with pollution from local or transported traffic emissions, can be observed in patients within hours of exposure. 

Researchers report that during the study, they analyzed the medical records of more than 1,700 patients admitted to the hospital for treatment of confirmed strokes between the years 1999 to 2008. The onset of stroke symptoms in each patient was reportedly matched to hourly measurements of particulate air pollution taken at the Harvard School of public Health’s environmental monitoring station. According to researchers, in this way they were able to estimate the hour in which stroke symptoms first occurred. The research team adds that it was able to calculate that the peak risk to patients from pollution exposure occurs 12 hour to 14 hours following exposure. Black carbon and nitrogen dioxide were linked closely with stroke risk, study results indicate.

“We think that this study is novel in that it has high-quality data on both air pollution exposure and stroke diagnosis,” Gregory Wellenius, ScD, lead author, assistant professor of community health at Brown University, says. 

Dan Costa, ScD, DABT, interim national program director for air climate and energy research in the US Environmental Protection Agency Office of Research and Developmental Research, emphasizes that in partnership with the National Institute of Environmental Health Sciences (NIEHS), “EPA funded this research advancing our understanding of air pollution and health effects.” Costa also notes that findings of Wellenius and his research team confirms and expounds upon a 2009 EPA integrated science assessment, which concluded that a casual relationship exists between PM2.5 and cardiovascular impacts. 

The study appears in the Archives of Internal Medicine.

Source: Beth Israel Deaconess Medical Center