Assessment of environmental carcinogen risks in terms of life shortening.

An approach is presented to the assessment of carcinogen risks in which the dominant effect of carcinogen exposure is life shortening and the impact falls both on those individuals who would have gotten cancer without the carcinogen exposure as well as the new cancer cases. This analysis is based on the interaction of age-specific tumor incidence rates and population survival in terms of age-specific mortality rates without the induced risk from carcinogen exposure. The analysis yields estimates for lifetime probability of developing cancer, average lifespan lost by the entire population, the average age of cancer occurrence, and the average lifespan loss of cancer cases. The approach utilizes the animal response data to assign, to the existing human cancer occurrence, and equivalent dose of the same carcinogen which is under consideration in terms of risk evaluation. The approach has the advantages of keying the estimates of carcinogen risks to those which already exist in the environment, advoiding large extrapolations from animal data, and encompassing the variability in susceptibility and carcinogen exposure in humans.