Long term exposure to smog can raise blood pressure: Study

A new review of studies has linked exposure to smog and other pollutants to a spike in blood pressure.

The findings stem from a review of 17 studies conducted around the world. Each assessed a possible link between blood pressure and dirty air related to common pollutants, such as vehicle exhaust, coal burning and airborne dirt or dust.

“Our results demonstrated that air pollutants had both short-term and long-term effects on high blood pressure risks,” said study author Tao Liu from Institute of Public Health in Guangzhou, China.

In the short term, he noted, a few days of increased air pollution could lead to more emergency hospital visits due to temporary spikes in blood pressure. In the long term, those living with consistently high levels of air pollution could end up with chronically high blood pressure.

According to background notes with the study, causes of high blood pressure (or “hypertension”) include genes, lifestyle habits, diet and environmental factors – probably including air pollution. Until now, evidence linking smog with high blood pressure has been controversial, Liu said in the study published in the journal Hypertension.

For this project, investigators analysed 17 studies conducted through August 2015. The studies involved roughly 328,000 people in all, about 108,000 of whom had high blood pressure.

Those investigations were conducted in Brazil, Canada, China, Denmark, Germany, Iran, Spain, Sweden, Taiwan and the United States. Short-term pollution exposure was defined as occurring over a number of days, and long-term exposure over a number of years.

In general, the research team defined high blood pressure as asystolic blood pressure reading (the top number) above 140 mm Hg and/or a diastolic blood pressure reading in excess of 90 mm Hg. Use of blood pressure medication was also an indication of high blood pressure.

The focus was on air pollutants such as nitrogen oxide, which stems from fossil fuels that power factories and cars; sulfur dioxide, also a fossil fuel emission; ozone; carbon monoxide; and particulate matter, such as tiny dust specks, dirt, smoke, and droplets of liquid.

Short-term exposure to pollutants such as sulfur dioxide and certain types of particulate matter appeared to boost the risk for high blood pressure. Also, long-term exposure to nitrogen oxide and particulate matter was linked to greater risk, the review indicated.

The findings didn’t establish a cause-and-effect relationship between these elements and elevated blood pressure. Also, while it appeared that ozone and carbon monoxide were tied to higher blood pressure, these two links did not reach “statistical significance,” the researchers said.