Media Watch: Smog Linked to Increased Stroke Risk

smoke and air pollution

smoke and air pollution

If you live in a county with “dirtier air” or high-levels of air pollution you have an increased risk of dying from a stroke and a shorter life expectancy, according to a new study that analyzed health data and pollution monitoring information from 1,561 counties across the United States between 2005 and 2010.

Led by Drexel University’s Longjian Liu, MD, PhD, an associate professor of epidemiology and biostatistics in the Dornsife School of Public Health, researchers examined the associations between county average, yearly air pollution (PM2.5) levels that contain inhalable particles — produced by diesel engines and the burning of coal, biomass and kerosene — and health issues (age-adjusted rates in adults 35 years and older). They looked at this type of air pollution as it has previously been shown to enter the circulatory system and harm health.

The researchers found:

  • The dirtier the air, the higher the rate of stroke deaths and shorter life expectancy in both men and women.
  • Higher the poverty rate and fewer health providers in a county, correlate with a greater health impact of high pollution.
  • Counties in the South had higher average yearly air pollution levels. The new results raise the possibility that exposure to this type of air pollution may be a factor in creating the “stroke belt” in the southern United States. Other possible contributors to excessive rates of stroke in these states are poverty, diet behavior, smoking, less control of stroke risk factors and limited availability of health services. Several states in the South had a much lower number of physicians available for patients as compared to the average number in the country.


Liu said that while the annual average PM2.5 was at a level considered acceptable, 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 in December 2012.

So what can clinicians do to help reduce the risk of stroke in patients exposed to elevated levels of pollution along with other risk factors?

“Clinicians 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,” said Liu in an American Stroke Association news release. “Clinicians can then encourage at-risk patients to take measures to reduce their exposure when possible, such as avoiding major roadways during rush hour traffic, keeping car windows closed and setting the air conditioner to circulate internal air.”

The study was presented in Honolulu at the American Stroke Association’s International Stroke Conference. Dozens of media across the country reported the story including U.S. News & World Report.

To schedule an interview with Longjian Liu, MD, PhD, contact Niki Gianakaris, executive director, Media Relations, University Communications, at 215-895-6741or

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