A significant study discovered that prolonged exposure to air pollution is associated with a heightened risk of developing blood clots in deep veins. If these clots are not addressed, they can obstruct blood flow and lead to severe health issues, including death.
The results emerged from a long-term study financed by the National Institutes of Health (NIH), which involved 6,651 adults from the U.S. who were observed for an average of 17 years between 2000 and 2018. Participants resided in or around six major urban centers: New York, Baltimore, Chicago, Los Angeles, Minneapolis, and Winston-Salem, North Carolina.
During the course of the study, 248 participants, or 3.7% of those studied, developed deep vein blood clots that necessitated hospitalization. The probability of this occurrence was correlated with an increase ranging from 39% to over double based on long-term exposure to three different categories of air pollutants.
Blood clots in deep veins, collectively termed venous thromboembolism (VTE), encompass conditions such as deep vein thrombosis—where a blood clot forms in a deep vein in the legs, arms, or an internal organ—and pulmonary embolism, which occurs when a clot dislodges from a deep vein and reaches the lungs.
Air pollution exposure, known to trigger inflammation and promote blood clotting, has been long-established as a risk factor for cardiovascular and respiratory ailments. Although earlier studies hinted at a connection to VTE, this research stands out as the largest and most detailed U.S. study to link VTE to three varied forms of air pollutants.
This study highlighted exposure to fine particulate air pollution measuring 2.5 micrometers or smaller, which can enter the lungs from multiple sources, such as smoke from coal-fired power plants, wildfires, and vehicle exhaust. Participants subjected to higher levels of this air pollution exhibited a 39% increased risk of VTE when compared to those with lower exposure levels. Additionally, those exposed to nitrogen oxides and nitrogen dioxide—pollutants mainly generated from vehicle emissions—showed an alarming 121% to 174% increase in risk.
To derive these conclusions, researchers examined the link between patients hospitalized for VTE and ambient air pollution levels gathered via thorough biweekly community monitoring, including samples obtained from participants’ residences. They analyzed and contrasted individuals with the highest exposure levels (top 75%) against those with the lowest (bottom 25%). They also performed several analyses to account for various factors associated with VTE, such as age, tobacco use, and pre-existing respiratory and health issues.
Annually, VTE impacts up to 900,000 Americans. Many incidents arise post-surgery, but additional risk factors like age, prolonged immobility, heart conditions, pregnancy, and genetic predispositions can heighten susceptibility.
The research is part of the Multi-Ethnic Study of Atherosclerosis (MESA) and received funding from contracts and grants from NIH’s National Heart, Lung, and Blood Institute, National Center for Advancing Translational Sciences, and the Environmental Protection Agency.
