SKELETAL PB-210 LEVELS AND LUNG-CANCER AMONG RADON-EXPOSED TIN MINERS IN SOUTHERN CHINA

A preliminary case-control study of 19 lung cancer cases older than 55 y and 141 age-matched controls was carried out among a group of underground miners in Southern China who were exposed to Rn-222 and its decay prodUCtS. Pb-210 activity levels were measured in the skull to estimate radon exposure. Radon exposure was also estimated in working level months, based on work histories and available industrial hygiene data. There was a smooth gradient of lung cancer risk with categories of skeletal Pb-210 level at time of last radon exposure; relative risks of 1.0, 2.9, 3.2, and 4.7 for categories <51.8, 51.8-77.7, 77.8-107.3, and greater-than-or-equal-to 107.4 Bq (<1,400, 1,400-2,099, 2,100-2,899, and greater-than-or-equal-to 2,900 pCi), respectively. Relative risks were unaffected by adjustment for exposure to arsenic in the mine or by adjustment for working level months. Risks also increased with cumulative working level month exposure, but the gradient of risk lessened after adjustment for exposure to arsenic. Pb-210, at the time of last radon exposure (rho = 0.13) and at the current Pb-210 level (rho = 0.01), was not highly correlated with the working level month estimate. Data were sparse but smoking had minimal effect on risk gradient with level of skeletal Pb-210 activity. This study suggests measured Pb-210 level may be a more precise predictor of lung cancer risk than working level month.