By AMERICAN HEART ASSOCIATION NEWS

For your heart’s sake, limit your time outdoors when pollution levels are high.

That’s the conclusion of researchers who recently found that short- and long-term exposure to air pollutants from coal burning, vehicle exhaust, airborne dust and dirt are associated with the development of high blood pressure – a major risk factor for heart disease and stroke.

“People should limit their exposure on days with higher air pollution levels, especially for those with high blood pressure,” said epidemiologist Tao Liu, Ph.D., lead author of the study published in the American Heart Association journal Hypertension. “Even very short-term exposure can aggravate their conditions.”

In the first study to simultaneously estimate the effects of short- and long-term exposure to air pollutants on high blood pressure by meta-analysis, researchers focused on these air pollutants:

Sulfur dioxide (SO 2 ) mainly comes from the burning of fossil fuel.

) mainly comes from the burning of fossil fuel. Nitrogen oxide (NO 2 ) comes from fossil fuels burned at power plants and vehicle exhaust.

) comes from fossil fuels burned at power plants and vehicle exhaust. Particulate matter (PM) are in the air and include dust, dirt, smoke and liquid droplets. (PM 2.5 is smaller than a speck of dust and is the most common and hazardous type of air pollution. PM 10 includes PM 2.5 and PM 2.5-10 ).

In the study, high blood pressure was significantly associated with short-term exposure to SO 2 , PM 2.5 and PM 10 and long-term exposure to NO 2 , which is produced from combustion, and PM 10 .

Researchers didn’t find significant short-term effects of ozone and carbon monoxide exposure.

Meta-analyses combine results from previous studies to estimate the overall effect of a particular variable on a result. Of 5,687 air pollution studies, researchers focused on 17 that included more than 108,000 people with high blood pressure and 220,000 people without high blood pressure.

Researchers defined high blood pressure as a systolic blood pressure of more than 140 mm Hg and/or a diastolic blood pressure of more than 90 mm Hg, or by use of high blood pressure medication. They assessed air pollution exposure by averaging data from the nearest air pollution monitoring stations or using complex dispersion models or land use regression models.

Previous studies have indicated that air pollution might be a risk factor for hypertension, but the results were controversial, said Liu, deputy director of the environmental health division at Guangdong Provincial Institute of Public Health in China. The mechanism by which air pollution could contribute to the development of high blood pressure includes inflammation and oxidative stress, which may lead to changes in the arteries.

“Next, we plan to further delve into the effects of particulate matter and their sources on hypertension risk, which we hope will inform air pollution control policymakers,” Liu said.