Abstract
We briefly review the evidence that the carcinogenic risk posed by inhaled fibers depends principally on the lung burden of long fibers. We use a deposition clearance model to generate time-dependent lung burdens in rats of a dozen long fibers for various exposure concentrations. Together with a previously estimated potency factor for long fibers, we use the generated lung burdens to estimate risks of lung cancer associated with inhaled fibers in rats. Over a broad range of exposure concentrations, excess risk is a linear function of exposure concentration. Excess risk of lung cancer is also a linear function of weighted half-life for fibers for which the weighted half-life is short compared to the life span of the rat. We propose an approach to estimating human lung cancer risk associated with inhaled fibers from animal studies.