Although high
radon concentrations have been linked to increased risk of
lung cancer by both experimental studies and investigations of underground miners, epidemiologic studies of residential
radon exposure display inconsistencies. The authors therefore decided to conduct a population-based case-control study in northwest Spain to determine the risk of
lung cancer associated with exposure to residential
radon. The study covered a total of 163 subjects with incident
lung cancer and a population sample of 241
cancer-free subjects since 1992-1994. Odds ratios for
radon were estimated using logistic regression adjusted for sex, age, lifetime tobacco use, family history, and habitat. The adjusted odds ratios for the second, third, and fourth quartiles of
radon (breakpoints: 37.0, 55.2, and 148.0 Bq/m(3)) were 2.73 (95% confidence interval (CI): 1.12, 5.48), 2.48 (95% CI: 1.29, 6.79), and 2.96 (95% CI: 1.29, 6.79), respectively. An additive synergic effect between
radon and tobacco was found. The results from this study suggest that, even at concentrations far below official guideline levels,
radon may lead to a 2.5-fold rise in the risk of
lung cancer. Furthermore, the synergy found between smoking and
radon may prove useful when it comes to drafting public health recommendations.