A biological model for lung cancer risk from 222Rn exposure

A model for lung cancer risk from 222Rn exposure was derived based on the following assumptions: 1) a cell nucleus in division (cycling) in the bronchial epithelium is the target for carcinogenesis; and 2) risk is proportional to the hit nuclei's ability to subsequently cycle. The model development required two steps. First, the number of cycling basal cell nuclei that can be traversed by an alpha particle following an exposure to 1 working level month (WLM) was calculated. Second, the model utilized measured cycling rates of basal nuclei in normal bronchial epithelium, to calculate the dividing population as a function of time post exposure. The basal nuclei cycling rates, from preliminary data, decreased with age with a half life of about 15 y. The shape of the model, as a function of time since exposure was compared with underground miner risk data, and the agreement was good.