an increased risk of blood clot?

The list of health problems associated with air pollution continues to grow. A large study funded by the National Institutes of Health (NIH) in the United States reveals that air pollution plays a key role in the development of blood clots in deep veins, known as venous thrombosis or phlebitis. These clots can obstruct blood flow and cause serious complications, sometimes fatal, if left untreated.

Why does pollution cause blood clots?

Published in the journal Bloodthe study followed for 17 years more than 6,600 adults residing in or near large American metropolises such as New York, Chicago and Los Angeles. Of this sample, 248 participants (3.7%) developed deep vein thrombosis requiring hospitalization. Pollution levels were measured every two weeks, including samples near the volunteers’ homes. The researchers compared the 25% of people with the least exposure to the 75% with the highest exposure, while taking into account factors like age, smoking and medical history.

According to scientists, the increased risk of venous thrombosis was linked to exposure to three types of air pollutants: fine particles (less than 2.5 micrometers), nitrogen oxides and nitrogen dioxide – substances released by road traffic exhaust, coal-fired power plants and forest fires. It appeared that “People exposed to high levels of fine particles had a 39% increased risk compared to those exposed to low levels,” according to a press release. As for exposure to oxides and nitrogen dioxide, mainly from vehicle emissions, it increased the probability from 121% to 174%.

Air pollution and systemic inflammation

If previous work has already established a link between pollution and cardiovascular or respiratory diseases, this is the largest American study carried out to date to highlight a direct link with deep vein thrombosis. Exposure to air pollution causes systemic inflammation, a key factor in the blood clotting process, scientists note in an attempt to explain this association.

Each year, deep vein thrombosis affects up to 900,000 Americans and between 50,000 and 100,000 French people, according to Inserm. Although many cases occur after surgery, other factors such as prolonged inactivity, age, heart disease, pregnancy and genetic predispositions can increase the risks. This study now adds air pollution to the list of potential dangers. Better monitoring of air quality and stricter public policies could help limit these risks to human health, the scientists conclude.