Researchers at Brown University and several other eastern universities have released a study concluding that exposure to high levels of traffic-related air pollution may be linked to stroke. Gregory A. Wellenius, et al., “Ambient Air Pollution and the Risk of Acute Ischemic Stroke,” Archives of Int. Med., February 13, 2012. Researchers reviewed the medical records of 1,705 Boston-area patients admitted to Beth Israel Deaconess Medical Center with a stroke between 1999 and 2008.

Using data from a local air pollution monitoring station, researchers calculated that the risk of having a stroke was 34 percent higher in the 24 hours after “moderate” Environmental Protection Agency (EPA) pollution readings compared to “good” pollution days. That increased risk was greatest within 12 to 14 hours of pollution exposure and was linked to nitrogen oxide, a traffic-related pollutant. Researchers reportedly found health concerns at levels generally considered safe by EPA, and the study recommends that the agency consider acceptable upper limits for air pollutants.