Scientists have long proposed a link between exposure to air pollution and high blood pressure levels. Now, a review of 17 studies lays down a clear support for the idea.

Led by epidemiologist Tao Liu, researchers from China conducted a meta-analysis of available studies from all over the world in order to assess the connection between dirty air from exhaust, airborne dust and coal burning and risk for hypertension.

More specifically, Liu and his colleagues focused on the following air pollutants: nitrogen oxide from burned fossil fuels and vehicle exhaust, sulfur dioxide from burned fossil fuels, and particulate matter (PM) such as dirt, dust, liquid droplets and smoke.

Scientists discovered that high blood pressure levels were strongly associated with short-term exposure to sulfur dioxide, PM 2.5, which is the most hazardous type of air pollutant, and PM 10. Long-term exposure to nitrogen dioxide and PM 10 were also greatly linked to high levels of blood pressure.

On the upside, researchers did not find any link to short-term effects of ozone as well as exposure to carbon monoxide. However, this aspect needs further investigation, they said.

How Air Pollution Affects Blood Pressure

For short-term exposure, a few days of increased air pollution could result to more emergency hospital visits. It's all because of temporary spikes in blood pressure, Liu said.

On the other hand, people living in areas with consistently high levels of air pollution and are exposed for a long time could develop chronically high blood pressure.

Still, the study has a caveat: it didn't exactly establish a cause-and-effect relationship between air pollution and high blood pressure, but it did acknowledge the association.

"There is a linear relationship between air pollution and hypertension," said Liu.

He said this suggested that even low levels of air pollution might contribute to risk of hypertension.

Keep Yourself Healthy

Blood pressure is a key marker for heart disease and stroke. It is also the number one cause of mortality around the world. Statistics reveal that soaring levels of blood pressure itself is connected to about 17 percent of deaths globally.

With that, Liu and his colleagues emphasized that it is urgent to take actions to ensure clean air quality, protect the environment and keep ourselves healthy.

Liu said that for now, people should focus on the quality of air every day.

In places with poor air quality, people should avoid outdoor activities or wear filtered masks. He also recommends using air purifiers while inside the house.

The details of the study are featured in the journal Hypertension on May 31.

Photo: David Holt | Flickr

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