Lung cancer and residency--a case-referent study on the possible impact of of exposure to radon and its daughters in dwellings.

In view of the well-known urban-rural difference in lung cancer rates, remaining also after standardization for smoking, it is suggested that low levels of radon and its daughters in dwellings might be of etiologic importance to this disease. To test this hypothesis, a case-referent (case-control) study was undertaken in a rural area; it considered residency in wooden houses (assumed to be associated with low-level exposure to radon and its daughters), "mixed type" houses (medium exposure) and stone houses (high-level exposure) among cases of lung cancer and referents (controls). The results indicate an increased risk of lung cancer among residents in "mixed type" and stone houses. Additional studies are highly desirable to confirm or refute these findings, which, if valid, mean increasing lung cancer hazards caused by a decrease in ventilation in future energy saving unless special measures are undertaken to reduce radon daughters in dwellings.