A retrospective look at Rn-induced lung cancer mortality from the viewpoint of a relative risk model

The potential contribution to U.S. lung cancer deaths from 1930 to 1987 from indoor 222Rn exposures is investigated from the standpoint of a constant relative risk model. Based on this model, which assumes a Rn risk proportional to the baseline lung cancer risk from other causes, the rate of Rn-induced lung cancer mortality has been increasing sharply since 1930. However, the estimated proportion of lung cancer deaths attributable to Rn has remained fairly constant. Applying the range of coefficients the U.S. Environmental Protection Agency employs in assessing the risk from indoor Rn, it is estimated that 8-25% of all current lung cancer deaths are "attributable to" past Rn exposures. The major sources of uncertainty in the estimates are discussed.