Preliminary research indicates that people who live in counties with dirtier air have higher rates of death from stroke and shorter life expectancies. There are some simple things residents of more polluted areas can do to reduce their exposure and lower their risk of stroke and cardiovascular damage from fine particles in the air, particularly if they have high blood pressure or other stroke risk factors.

Researchers analyzed health data and pollution monitoring information from 1,561 counties across the United States between 2005 and 2010. They examined the average yearly levels air pollution containing fine inhalable particles, known as PM2.5. This type of pollution is produced by diesel engines and the burning of coal, biomass and kerosene, and has been shown to enter the circulatory system and harm health.

The highest impact on stroke was in the South, raising the possibility that exposure to PM2.5 pollution may be a factor in the so-called "stroke belt" in the southern United States.

The yearly average for fine air pollution ranged from 7.2 to 14.7 (average 11.75) micrograms per cubic meter. “Overall, the annual average was at a level considered acceptable. However, 51 percent of counties had an annual average exceeding 12 micrograms per cubic meter, the annual average limit of the National Air Quality Standards for PM2.5 set by the Environmental Protection Agency (December 2012),” explained Longjian Liu, lead author of the study and an associate professor of epidemiology and biostatistics at Drexel University in Philadelphia.

Looking at the associations between county average PM2.5 pollution levels and health measures in adults 35 years and older, the team found the dirtier the air was in a county, the shorter the life expectancy for both men and women and the higher the rate of death from stroke. The highest impact on stroke was in the South, raising the possibility that exposure to PM2.5 pollution may be a factor in the so-called “stroke belt” in the southern United States.

Poverty, diet, smoking and a lack of available health services also raised the risk of stroke deaths in any given location.

Liu wants people to know there are things they can do protect themselves and elderly family members from the health effects of pollution. People at-risk should reduce their exposure when possible by avoiding major roadways during rush hour traffic, keeping car windows closed and setting the air conditioner to circulate internal air. Doctors, too, should factor in a person's pollution exposure.

“To reduce the risk of stroke, clinicians should consider their patients' likely exposure to air pollution along with other risk factors. They can ask patients whether they live or work in an urban industrial area or whether they are aware of sources of pollution near their home or workplace,” Liu adds. Doctors can then use this information to take further steps to prevent stroke.

The researchers are also examining the association between higher levels of PM2.5 pollution and a greater risk of other leading causes of death, including coronary heart disease, heart failure and cancer.

The research is to be presented in Honolulu at the American Stroke Association's International Stroke Conference.