Application of Estimated Excess Lifetime Cancer Risk in Field Situations

Abstract

The term “excess lifetime cancer risk” connotes the risk of death of cancer in excess of the “natural” background risk, resulting from a lifetime exposure to carcinogens. In practice, exposure is not for a lifetime, competing causes are prominent, the exposure usually comprises more than one carcinogen, and the risk of cancer death may be substantially reduced by therapy. Therefore, the following points and questions and questions may be considered. (1) The estimated excess unconditional risk based on animal bioassays overestimates the risk for humans. A conditional risk, however, would require life-table techniques, for which age-specific mortality rates are essential but difficult to obtain. (2) For a shorter-than-lifetime exposure, the Weibull time model appears to be inadequate because it does not accommodate for the probable significant reduction of additionally accrued incremental risk after cessation of exposure. (3) Should the level of risk used for initiating public health activities be the same as that for initiating remedial actions? (4) When populations are exposed to multiple chemicals, should decisions concerning public health be based on the sum of the risk estimates for all of the chemicals or on the highest risk estimate for one chemical? (5) When small populations are exposed, should the predicted actual excess number of cancer deaths rather than a predicted risk level be the sole basis for decisions on public health and remedial action?