Residential radon exposure is a significant contributor to lung cancer in Europe, with smokers most vulnerable to its effects, according to an article in the January 29th issue of the British Medical Journal.

Researchers analyzed 7,148 cases of lung cancer and 14,208 controls across Europe. In the largest study of its kind, radon levels in the present and past homes of all lung cancer patients and controls were examined. Investigators also obtained detailed smoking histories, including the effects of second-hand smoke on lifelong non-smokers.

The researchers found that radon accounted for 20,000 deaths from lung cancer in Europe each year, roughly 9 percent of lung cancer deaths and 2 percent of all cancer deaths. The risk of radon-induced lung cancer increased proportionally with degree of radon exposure. Smokers were at much greater risk for lung cancer because radon exposure multiplied the effects of smoking.

For researchers who might want to compare local conditions with those existing in the study area (nine European countries), the mean measured radon concentration in control homes was 97 becquerels (disintegrations per second) per cubic meter of air. In contrast, mean level was 104 becquerels per cubic meter for past and present homes of lung cancer patients, an increase of 16 percent after adjustment for uncertainty in radon measurements.

In addition, analysis found that proportional excess risk due to radon did not differ significantly with age, gender, or smoking.