Previous research has already established a link between particulate levels and heart disease but the study published in this month’s issue of Stroke, journal of the American Heart Association, is the first to demonstrate the connection between fine and ultrafine particulate matter and stroke rates.

Fine particles, PM25, typically come from exhaust fumes, power plant emissions and other operations which involve burning fossil fuels while ultrafine particles, PM25, are typically found in fresh traffic emissions.

“We evaluated the effects of these and other particle sizes on stroke to help determine the most harmful particle sources in the air,” said Jaana Kettunen, lead author of the study and researcher for the National Public Health Institute in Kuopio, Finland.

Researchers examined data from 1998 to 2004 associating daily air pollutant levels and daily stroke mortality counts among people ages 65 and older in Helsinki.

They studied analyses in the warm and cold times of year.

“We found that during the warm season, there was a positive association between stroke mortality among the elderly and current-day level of fine particles,” said Ms Kettunen.

“There was a 6.9% increase in stroke death for every 6ug/m3 increase in fine particles. In addition, there was 7.4% increase in stroke mortality for every 6ug/m3 increase of previous-day fine particle levels.

“We observed associations also for previous-day levels of ultrafine particles and carbon monoxide, but these associations were less robust. Coarse particles were not statistically significantly associated with stroke deaths.”

Researchers found no associations in the cold season with fine particles, ultrafine particles or carbon monoxide.

The authors suggest that people might be more vulnerable to air pollution in warmer months because they are outside and open their windows and doors more than in cold months and thus their exposures are higher.

Alternatively, differences in air pollution mixture between seasons may play a role.

The study’s findings have many implications for the elderly, Kettunen said.

“We suggest that on high pollution days, elderly people should avoid spending unnecessary time in traffic, whether in a vehicle or walking, especially if they suffer from cardiovascular diseases, to lower their exposure to pollutants,” she said.

“They should also avoid heavy outdoor exercise on high air pollution days. And nursing homes, for example, should not be built along heavily trafficked roads, where particle concentrations are at their highest.”

Sam Bond

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