A new study suggests that breathing air polluted with fine particulate matter increases the risk of several types of stroke, including ischemic and hemorrhagic strokes.
In findings published last week in the medical journal The BMJ, Chinese researchers evaluated the side effects of long-term exposure to air that contains small particles of pollution with a diameter less than 2.5 μm, which is 30 times smaller than a single strand of human hair.
The research was conducted in 15 Chinese provinces, evaluating data on more than 117,500 men and women with no history of having a stroke. The study was a part of the Prediction for Atherosclerotic Cardiovascular Disease Risk in China (China-PAR) project.
Researchers found that long-term PM 2.5 levels were 64.9 μg/m3 on average from 2000 to 2015 at participants’ residential addresses. During that time, more than 3,500 strokes occurred among participants. The findings indicate that 63% were ischemic, when a blood vessel becomes blocked and doesn’t allow blood flow to the brain, and 27.5% were hemorrhagic, when a blood vessel in the brain bursts and causes bleeding in the brain.
The data indicates participants in the highest quarter of exposure, reaching over 78.2 μg/m3 of PM 2.5, had a 53% increased risk of stroke, including ischemic stroke and hemorrhagic strokes.
For each increase of 10 μg/m3 in PM 2.5 concentrations, the risk increased 13% for any type of stroke, 20% for ischemic, and 12% for hemorrhagic strokes.
Prior studies have shown exposure to air pollution can have serious health effects, including increasing the risk of stroke. Another study published in 2016 indicated air pollution can cause heart disease by damaging blood vessels and decreases the risk a person will survive a heart transplant.
Even short-term air pollution exposure can increase the risk of death from heart and lung problems according to previous research. Another study linked moderate air pollution to lung damage similar to that seen among long-term smokers.
An estimated 1.6 million people in China die each year from heart lung and stoke problems linked to polluted air. Fine particulate matter air pollution has been linked to the deaths of more than 30,000 Americans each year.
After years of improvement in U.S. air quality, the levels of air pollution in the U.S. have worsened according to another recent study.
“This study provides evidence from China that long term exposure to ambient PM2.5 at relatively high concentrations is positively associated with incident stroke and its major subtypes,” wrote study authors. “These findings are meaningful for both environmental and health policy development related to air pollution and stroke prevention, not only in China, but also in other low and middle income countries.”