Bad Air

High blood pressure linked to short-, long-term exposure to some air pollutants.

Both short- and long-term exposure to some air pollutants commonly associated with coal burning, vehicle exhaust, airborne dust and dirt are associated with the development of high blood pressure, according to research in the American Heart Association’s journal Hypertension.

“In our analysis of 17 previously-published studies we discovered a significant risk of developing high blood pressure due to exposure to air pollution,” said Tao Liu, Ph.D., lead study author and deputy director and epidemiologist of the environmental health division at Guangdong Provincial Institute of Public Health in China. “People should limit their exposure on days with higher air pollution levels, especially for those with high blood pressure, even very short-term exposure can aggravate their conditions.”

Researchers performed a meta-analysis, combining results of available published studies to estimate the overall health effects of all air pollution on hypertension risk. In the first study to ever simultaneously estimate the effects of short-term and long-term exposure to air pollutants on hypertension by meta-analysis, researchers focused on a variety of air pollutants.

The meta-analysis found high blood pressure was significantly associated with short-term exposure to:

  • Sulfur dioxide (SO2 ), which mainly comes from the burning of fossil fuel, and
  • Particulate matter, which the U.S. Environmental Protection Agency (EPA) describes as particles of dust, dirt, smoke and droplets of liquid in the air, smaller than 10 micrometers in diameter (PM10), that we breathe in and that can accumulate in our respiratory system. Fine particles that are less than 2.5 micrometers in diameter (PM2.5) are believed to have the greatest health risk because they are so small that they can lodge deep in the lungs.

It also found that high blood pressure was significantly associated with long-term exposure to nitrogen dioxide (NO2) which comes from fossil fuels burned at power plants and is also in vehicle exhaust and long-term exposure to PM10 particles.

For the portion of the study that assessed short term effects of nitrogen dioxide, ozone and carbon monoxide exposure, no significant associations were found. Researchers said that the links between short term exposure to these chemicals and high blood pressure requires further study.

Of the 5,687 air pollution studies initially screened, 17 were the focus of this meta-analysis — which involves more than 108,000 hypertension patients and 220,000 non-hypertensive controls. Several of the studies defined high blood pressure as: 1) systolic blood pressure more than 140 mm Hg and/or diastolic blood pressure over 90 mm Hg or 2) by antihypertensive drug use.

Previous studies have indicated that air pollution might be a risk factor for hypertension but the results were controversial, Liu said. Air pollution could contribute to the development of high blood pressure through factors including inflammation and oxidative stress, which may lead to the arteries becoming stiffer.

“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.

Source: American Heart Association News

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