Alkaline single cell gel electrophoresis and human biomonitoring for genotoxicity: a study on subjects with residential exposure to radon

Based on theoretical estimates and various correlation studies, it has been suggested that ingestion of radon in drinking water represents an increase d risk for cancer. Such a risk has never been conclusively shown in epidemi ological or experimental animal studies, however, and it has been questione d whether the radon level in the drinking water is of any significance in t erms of overall radon exposure. Using primary DNA damage as a biological ma rker for an ongoing exposure to ionising radiation, the present study was u ndertaken to investigate whether people with different types of residential radon exposures differed with regard to their levels of DNA damage in circ ulating lymphocytes. DNA damage was measured in coded blood samples from 12 5 residents living in 45 households with different levels of radon-222 in t he drinking water (10-2410 Bq/1) and indoor air (35-1025 Bq/m(3)) using alk aline single cell gel electrophoresis (the 'Comet' assay). Increased levels of radon in indoor air (> 200 Bq/m(3)) were found to be associated with an increased level of DNA damage in peripheral lymphocytes (P less than or eq ual to 0.05). No such correlation was seen for the radon concentrations in the drinking water, and there was no obvious relationship between the radon levels in drinking water and in indoor air. The results of the present stu dy suggest that measures taken to reduce residential radon exposures should be focused on reducing radon levels in indoor air rather than minimising r adon levels in drinking water. (C) 1999 Elsevier Science B.V. All rights re served.