Exposure to air pollution from traffic fumes raises risks of
potentially fatal blood clots in the leg; it alters the blood’s coagulation
properties and heightens the risk of deep vein thrombosis (DVT), a Harvard research
study showed.
The Harvard School of Public Health published the results of
the first study focused on air pollution’s effects on clotting in the veins in
the May 12 issue of Archives of Internal Medicine.
Harvard researcher Andrea Baccarelli, MD, PhD, and her
colleagues studied 870 patients diagnosed with blood clots in the leg from 1995
to 2005. They compared the particular air pollution exposure of people
diagnosed with DVT in the year before their diagnosis in the Lombardy region of
northern Italy
to that of more than 1,000 people in a control group free of blood clots. Blood
clots which form in the legs can travel to the lungs, where they can become
lodged, triggering a potentially fatal pulmonary embolism.
The scientists measured the amount of small particles, tiny
chemicals caused by burning fossil fuels, and liquid droplets in the Lombardy
region of Italy
in a study of 2,000 people.
Researchers found that those exposed to higher levels of
small particles in the air before being diagnosed with DVT were more likely to
develop blood clots. The risk of developing a DVT went up by 70% for every 10
microgrammes per square metre increase in small particles.
The association was weaker in women than in men because they
used oral contraceptives or hormone therapy, which also had procoagulant
effects.
“We surmise that prothrombotic mechanisms are already
activated in [women] receiving hormone therapy so that they undergo less or no
further induction after air particle exposure,” the authors said.
“Given the magnitude of the observed effects and the
widespread diffusion of particulate pollutants, our findings introduce a novel
and common risk factor into the pathogenesis of DVT and, at the same time, give
further substance to the call for tighter standards and continued efforts aimed
at reducing the impact of urban air pollutants on human health,” the authors concluded
in the study.
“It's an exciting finding because air quality is something
we can improve on through tightening air quality legislation.”
