Exposure to Long Term Air Pollution May Increase Risk for Venous Blood Clots: Study Finds

A large study found that greater exposure to long-term air pollution was linked with increased risks for blood clots that can occur in deep veins, which, if untreated, can block blood flow and cause serious complications, even death. The findings were published in the journal Blood.

These findings came from a longitudinal study that included 6,651 U.S. adults who were followed for an average of 17 years between 2000 and 2018. Participants lived in or near one of six major metropolitan areas: New York, Baltimore, Chicago, Los Angeles, Minneapolis, and Winston-Salem, North Carolina.

Throughout the study, 248 adults, 3.7% of the study sample, developed blood clots in deep veins that required hospital care. The likelihood of this outcome was linked to anywhere from a 39% to a more than two-fold increased risk based on long-term exposure to three different types of air pollutants. Exposure to air pollution, which can set the stage for inflammation and contribute to blood clotting, has long been associated with cardiovascular and respiratory diseases.

This included exposure to tiny air pollution particles equal to or less than 2.5 micrometers, which can be inhaled from a variety of sources. Participants with greater overall exposure to this type of air pollution had a 39% increased associated risk for venous thromboembolism compared to people exposed to lower levels. People with increased exposure to oxides of nitrogen and nitrogen dioxide, pollutants most often found from vehicle exhaust, had a respective 121% to 174% increased risk.

To reach these findings, the researchers analyzed the relationship between patients hospitalized for venous thromboembolism and levels of air pollution collected through extensive biweekly community-level monitoring — including samples taken from the homes of participants. They then compared those with the highest exposure levels — the top 75% — to those with the lowest exposure — the bottom 25%. They also conducted multiple analyses to control for variables associated with venous thromboembolism, such as age, exposure to tobacco, and underlying respiratory and other health conditions.

Reference: Lutsey P, Misialek J, Young M, et al. Air pollution is associated with increased risk of venous thromboembolism: The Multi-Ethnic Study of Atherosclerosis. Blood. 2024; doi: https://doi.org/10.1182/blood.2024026399.