Long-term exposure to air pollution may worsen the risk of dangerous blood clots

Chronic exposure to common air pollutants significantly increases the risk of blood clots forming in deep veins of the body, according to a long-term observational study that followed more than 6,600 adults in six major U.S. cities. There is a possibility that it will happen.

People living in areas with the highest exposure to outside air pollution, such as car exhaust and smoke from forest fires and coal-fired power plants, face the greatest risk of developing the disease. Venous thromboembolism (VTE)research shows.

VTE is estimated to affect up to 900,000 Americans. CDC. If left untreated, blood clots in veins deep in the body, such as in the lungs or muscles of the legs and arms, can block blood flow and cause serious complications and even death.

Previous research has shown that there is a relationship between Researchers say this is the most comprehensive and detailed study in the United States examining VTE from three air pollutants, targeting air pollution and venous thromboembolism.

This study adds to the growing body of evidence that all levels of air pollution have been associated with air pollution for many years. Atherosclerotic cardiovascular (ASCVD) Respiratory diseases have a negative impact on health. pregnancy and childhood.

“Importantly, air pollution is so ubiquitous that even modest associations can cause large numbers of pollution. [health] said “event” Dr. Pamela Latseyprofessor of epidemiology and community health at the University of Minnesota. “What's surprising is that these pollutants are so common in the air that most of us breathe, that they may be increasing our risk without us even realizing it. is.”

“Even when we looked at people without evidence of lung disease or smoking, we found an association between air pollution and VTE risk.”

Study results announced Thursday [Dec. 12, 2024) in the American Society of Hematology’s Blood Journal, show:

• A 3.6 microgram per cubic meter (µg/m³ ) increase in fine particulate matter (tiny air pollution particles of 2.5 micrometers or less, PM_2.5) was linked to a 39% higher risk of VTE.  
• A 13.3 parts per billion (ppb) increase in nitrogen dioxide (NO₂) was linked to a 174% higher risk.
• A 30 ppb increase in nitrogen oxides (NO_x) was linked to a 121% higher risk.

Notably, 348 study participants (3.7%) developed blood clots in deep veins that required hospital care, the researchers say.

The findings suggest that air pollution is independently associated with VTE, and not just increasing VTE risk through its role in respiratory disease, Lutsey says. Air pollution may  increase inflammation in the body, she says, and also increase levels of clotting (coagulation) factors in the blood.

“Often when I think about air pollution, I think about a very small increased risk,” Lutsey said. “The strength of associations was stronger than I had honestly expected.”

Nearly twofold risk of developing VTE with highest PM_2.5 exposure

VTE is an umbrella term for blood clots that develop in the deeper veins of your body. It consists of:

• Deep vein thrombosis (DVT), which occurs when a blood clot forms in a deep vein of the legs, arms, or an internal organ
• Pulmonary embolism (PE), which occurs when a blood clot breaks off from a deep vein and travels to the lungs

Chronic thromboembolic pulmonary hypertension, among other complications, may also occur after a PE with a large clot. It stops blood from reaching the lungs and can be fatal.

This latest research is part of the Multi-Ethnic Study of Atherosclerosis (MESA), which recruited participants in 2000-2002. They ranged in age from 45 to 84 years old and came from four groups: white, Black, Hispanic, and of Chinese ancestry. Half were female. All lived in or near New York, Baltimore, Chicago, Los Angeles, Minneapolis, and Winston-Salem, North Carolina.

Throughout the study, researchers updated air pollution metrics in each community every two weeks. They also followed participants, assessing their exposures, over an average of nearly 17 years between 2000 and 2018.

The researchers then compared those with the highest exposure to air pollutants—the top 75%—to those with the lowest—the bottom 25%. They found people in the top percentile had:

• 43% greater risk of developing VTE with elevated PM_2.5 exposure
• 2.8% great risk with elevated NO₂ exposure
• 2.3 times greater risk with higher NOx exposure

Among other limitations, the results of the study may not be transferable to the entire U.S. because it included only six communities, although they were diverse, the researchers say. Also, they identified VTE incidents using hospital discharge codes, misclassifications may have occurred and outpatient cases missed. 

Reducing air pollution worldwide would improve public health, the researchers say.

“This study supports the case for global efforts of pollution reduction to curtail pollution-related adverse health outcomes, which we demonstrate includes risk of VTE.”

Reference

Lutsey PL, Misialek JR, Young MT, et al. Air pollution is associated with increased risk of venous thromboembolism: The multi-ethnic study of Atherosclerosis. Blood Journal. Published online December 12, 2024. doi:10.1182/blood.2024026399

• Azzouz M, Xu Y, Barregard L, et al. Long-term ambient air pollution and venous thromboembolism in a population-based Swedish cohort. Environ Pollut. 2023;331(Pt 1):121841. doi:10.1016/j.envpol.2023.121841 [Abstract]
• Lin DS, Lo HY, Hwang KC, Lin TT, Lee JK, Lin LY. Long-term exposure to air pollution and risk of venous thromboembolism: a national population-based retrospective cohort study. Clin Less Cardiol. Published online on August 19, 2024. doi:10.1007/s00392-024-02495-2 [Abstract]
• Renzi M, Stafoggia M, Michelozzi P, Davoli M, Forastiere F, Solimini AG. Long-term exposure to air pollution and risk of venous thromboembolism in a large administrative cohort. environmental health. 2022;21(1):21. Published January 27, 2022. doi:10.1186/s12940-022-00834-2