cancer risk: risk increased as exposure rate decreased. Two models were described, one describing the exposure-rate effect by variables for the duration of exposure and the other by variables for exposure rate.

Early in its deliberations, the committee critically assessed the various possible approaches to risk estimation from exposure to low levels of radon. The possible methodologies for generating such risk estimates are summarized in Figure 1-3, and are discussed in chapter 3. In addition to the previously used dosimetric and epidemiologic approaches, statistical models can also be applied that are based on a biologic construct of the effect of radon.

The dosimetric approach focuses on computing the doses deposited in lung target cells by alpha particles emitted from radon progeny deposited in various compartments of the lung. The approach relies on applying risk estimates from

FIGURE 1-3 Possible methodologies for generating risk estimates for low exposures to radon.