Air pollution, even at levels considered safe, are anything but, according to a new study.
A report, published in the Feb. 14 issue of the Archives of Internal Medicine, by researchers from Beth Israel Deaconess Medical Center in Boston, found that exposure to ambient fine particulate matter, usually from vehicle traffic, was associated with a significantly higher risk of ischemic strokes on days when the Environmental Protection Agency's air quality index for particulate matter was yellow instead of green.
The researchers concluded the odds of having a stroke were 34 percent higher on or following moderate air quality days.
Researchers analyzed more than 1,700 medical records of patients in the Boston area who went to the hospital for treatment of confirmed strokes.
They matched the onset of stroke symptoms in each patient to hourly measurements of particulate air pollution taken at the Harvard School of Public Health's environmental monitoring station.
The particles, known as PM2.5, came from a variety of sources including power plants, factories, trucks and automobiles, and the burning of wood.
Researchers found that black carbon and nitrogen dioxide, two pollutants associated with vehicle traffic, were closely linked with stroke risks.