WEDNESDAY, March 23 (HealthDay News) -- Exposure to high levels of traffic pollution doubles the risk of organ rejection and death in lung transplant patients, a new study suggests.

Belgian researchers tracked the health of 281 lung transplant patients over a five-year period, and found that 117 (41 percent) developed a serious inflammatory condition called bronchiolitis obliterans syndrome. Of those patients, 61 died.

The syndrome, which is caused by an overactive immune system and is the clinical equivalent of organ rejection, is common in lung transplant patients.

The researchers found that patients who lived within 171 meters (187 yards) of a main road were twice as likely to develop the syndrome and more than twice as likely to die within five years, compared to patients who lived farther away from a main road.

The study authors also concluded that every tenfold increase in distance from a main road was associated with a 43 percent reduced risk of developing the syndrome and a 28 percent reduced risk of death.

Gender, age or type of lung transplantation (single or double) had no effect on the risk of death.

The researchers also found that the farther patients lived from a main road, the lower their levels of inflammatory markers.

The findings suggest that one in four cases of bronchiolitis obliterans syndrome and 28 percent of deaths in lung transplant patients could be attributed to living near a major road, the researchers concluded.

"Traffic related air pollution appears to constitute a serious risk ... If confirmed by other studies, [it] has substantial clinical and public health implications," the researchers noted.

The study appears online in the journal Thorax.

More information

The U.S. National Heart, Lung, and Blood Institute has more about lung transplantation.