Assessment of exposure of uranium miners to radon progeny using in vivo measurement of 210Pb in bone

Epidemiological studies of lung cancer incidence among uranium miners from various populations around the world have shown a significant variability in the relative risk per unit exposure - a range of a factor of 30. A significant fraction of the uncertainty associated with these risk coefficients may be due to differences in the methods and quality of data used in calculating cumulative exposures, in Working Level Months (WLM), for the various miner populations. We hypothesize that in vivo measurement of 210Pb, a long-lived radon decay product, retained in bone will provide a better measure of the exposure of individual miners to radon and progeny during their mining careers. To accomplish these in vivo measurements, the Lovelace Respiratory Research Institute (LRRI) In Vivo Bioassay Facility (IVBF) was modified to optimize a counting geometry for measuring 210Pb in the skull. Six phoswich detectors (12.7 cm diameter) were positioned about the head of a reclining subject (one posterior, one anterior, and four on the sides of the head), and photon emission from the skull was measured using anticoincidence multichannel analysis electronics. To date, we have analyzed the in vivo measurement data from about 90 former uranium miners from the Grants, New Mexico (NM), mining district. The recorded WLM exposures for each uranium miner (data from the UNM epidemiological data base) were compared with a WLM exposure calculated using a Pb biokinetic model coupled to the ICRP Publication 66 respiratory tract dosimetry model. The analyses show that the independent measures of exposure are statistically correlated but vary greatly among individual values. (author)