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| health information | health news

Air pollution raises risk of DVT

15 May 2008

This study opens up a whole new avenue of research into the
causes of DVT.

Dr Beverley Hunt, medical director, Lifeblood, The Thrombosis Charity

Key facts

DVT is a condition where a blood clot forms in a deep vein, usually in the leg. DVT can cause pain and swelling.
DVT can be dangerous if the clot or part of the clot travels through the blood to the lungs. This can block the arteries that supply them (pulmonary embolism).
The risk of DVT is not very high, but can be increased by certain factors including periods of immobility, such as after major surgery, or if you have had a heart attack or stroke.

Breathing polluted air increases the danger of developing deep vein thrombosis (DVT), US research suggests.

The study, carried out by scientists at the Harvard School of Public Health, indicates that high levels of particulate air pollution - microscopic particles emitted by factories and vehicles - make blood "stickier" and more likely to clot in veins.

"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," explains lead researcher Dr Andrea Baccarelli, in the Archives of Internal Medicine.

Using data from 53 pollution monitors throughout the Lombardy region in Italy, the team examined how exposure to tiny particles in the air affected blood clotting and the risk of DVT in over 2,000 people.

The team recruited about 900 people who developed DVT from the general population in Lombardy between 1995 and 2005. They then recruited around 1200 volunteers of a similar age without the condition, and compared how polluted the air was where they lived.

Dr Baccarelli and colleagues found that the higher the level of air pollution exposure was in the previous year, the greater the risk of DVT. For every 10 micrograms of air pollution particles per square metre, the risk of DVT increases by 70 percent. Because DVT is so rare, this would only be a very small number of extra people.

And the team found that higher levels of air pollution were associated with faster blood clotting in laboratory tests.

The study is one of the few to suggest a link between air pollution and DVT. Previous research has already shown that air pollution increases the risk of stroke and heart attack.

The researchers monitored particles less than 10 millionths of metre (micrometers) in diameter, called PM10. PM10 can be produced by vehicle exhaust, airborne dust, burning coal, incineration and the metals industry.

Dr Baccarelli said their study adds to the call for "tighter standards and continued efforts aimed at reducing the impact of urban air pollutants on human health".

Dr Beverley Hunt, medical director of the charity Lifeblood, The Thrombosis Charity, told the Bupa health information team, "This study opens up a whole new avenue of research into the causes of DVT.

"It's a very exciting finding."