Residential Radon, Smoking and Lung Cancer Risk. A Case-Control Study in a Radon Prone Area

Abstract

Background. Residential radon is the second risk factor of lung cancer following tobacco consumption and the main one in never smokers, according to the WHO and USEPA statements. The joint effect of tobacco and radon exposure has been little studied and residential radon is a neglected risk factor of this disease. We aim to show lung cancer risk for different combinations of tobacco consumption and residential radon exposure on the risk of lung cancer.

Method. Pooling case-control study in a radon-prone area where we have combined individual information from 5 different multicentric case-control studies. 11 Spanish hospitals from 4 different regions have taken part. All case-control studies had a similar methodology, including incident, primary, and histologically confirmed lung cancer cases and controls attending hospital for trivial surgery not related with tobacco consumption. Cases and controls were older than 30 and controls were matched with cases using a frequency-based sampling using age and gender distribution of cases. Detailed information was obtained regarding tobacco consumption, and a radon device was placed in the participants’ dwelling for at least three months. We calculated lung cancer risk for each category of tobacco consumption and radon exposure taking as a reference those participants never smokers and with an indoor radon concentration below 50 Bq/m3. All Odds Ratios are accompanied by their 95% confidence intervals.

Result. We included 1691 cases and 1698 controls with a similar distribution on age and gender. Heavy smokers exposed to low radon concentrations (< 50Bq/m3) posed a risk of lung cancer of 12.6, compared to 31.3 for heavy smokers exposed to indoor radon higher than 200 Bq/m3. The different odds ratios and confidence intervals for each category of exposure appear in the Table.

Conclusion. There is an interaction between indoor radon and tobacco. Risk of lung cancer increases significantly when both risk factors are present.