A study conducted in an area of Italy where residential radon levels are high confirms that the risk of lung cancer increases in step with levels of radon exposure, but that the Mediterranean diet may modify the effects.

In the study, researchers examined the association between indoor radon exposure and lung cancer in 384 "case" patients with lung cancer and 404 control patients without lung cancer. They considered the potential role of smoking, diet, and other risk factors.

The researchers determined residential history during the 30-year period ending 5 years prior to enrollment. Radon detectors were placed in the main bedroom and the living room in each residence for two consecutive 6-month periods.

Confirming prior studies, the researchers found a positive link between indoor radon and lung cancer. The odds of developing lung cancer rose with increasing levels of residential radon exposure, the investigators report in the International Journal of Cancer.

Overall, the increase was generally not statistically significant, although significance was reached for some high radon exposure categories.

Dr. Francesco Forastiere, of the Rome E Health Authority, and colleagues say their results may prompt radon legislation in the Mediterranean area, "where such regulations are generally lacking."

They also report that individuals with low-medium consumption of dietary oxidants tended to be at greater risk for developing lung cancer.

The possibility that dietary antioxidants may modify the effects of radon on lung cancer risk should be studied further, they conclude.

SOURCE: International Journal of Cancer, May 10, 2005.