Finnish scientists have come up with a study they believe to be the first to evaluate the contribution of fine particle pollution to stroke risks in the elderly.
Fine particle pollution is made up of tiny particles of dust and soot, less than 2.5 microns, about 1/30th the width of a human hair. They mostly come from car exhaust, power plant emissions and burning of fossil fuels. Ultra-fine particles are less than 0.1 microns and are usually found in car exhaust.
Dr. Jaana Kettunen, from the National Public Health Institute in Kuopio, and colleagues compared air pollution levels from 1998 to 2004 with the number of stroke deaths among elderly subjects above 65 years, living in Helsinki.
A total of 1,304 stroke deaths in the warm season and 1,961 in the cold season were recorded during the study period.
When outdoor levels of fine particle pollution were high, fatal stroke risk rose; but only during Helsinki's warm season, it was seen.
Results were published in the journal Stroke.
During the warm season, every 6 microgram per cubic meter increase in current-day levels of fine particulate air pollution was associated with a 6.9 percent increase in deaths from stroke.
The corresponding stroke death rate for previous-day fine particulate increases was 7.4 percent. However, particulate air pollution had no effect on stroke during the cold season.
Previous-day levels of ultra fine particles plus carbon monoxide were also linked to stroke mortality.
Yet, Kettunen says that "these associations were less robust" than those seen with fine particulate pollution.
"Coarse particles were not statistically significantly associated with stroke deaths." she adds.
"Our results suggest that the levels of combustion-
originating particles rather than coarse particles explain the association between particulate matter and stroke.
"Thus, regulatory efforts should be focused on reducing emissions of combustion particles.
"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," concludes Kettunen.
"They should also avoid heavy outdoor exercise on high pollution days, and nursing homes, for example, should not be built along heavily trafficked roads, where particle concentrations are at their highest." she adds.