EsEr GUEST EDITORIAL

Cancer risk assessment: Evolution in a fishbowl

Both the science and the practice of risk assessment are evolving. This lack of maturity presents a problem both for regulatory programs and for regulated industries. The problem arises from two public perceptions. The first is the perception of cancer as a dread disease, a consequence of medical and political salesmanship. The second is the perception of risk assessment as a process, a result of attempts to display the science and uncertainties inherent in risk assessment for all to see. Although I could emphasize the positive attributes of this public perception, I have chosen to call it a prob- lem here because this perception goes hand in hand with a realization that cancer risk assessment is not as precise as it should be for optimal use in regulatory decision making.

No one will dispute that it was and continues to be important to identify potential human carcinogens with animal tests. However, the usefulness of obtaining that information with a few exposure levels at or near the maximum tolerable for a lifetime remains problematic. Although reliance on the practice of risk assessment in recent environmental laws has moved us away from the zero-risk concept of Delaney, we have come only as far as describing the quantitative nature of cancer risk in terms of a plausible upper bound. There is currently little scientific consensus on how to provide a maxi- mum likelihood or best estimate of risk in other than purely statistical terms; that is, in terms supported by our understanding of both the biology and the biochem- istry of the human disease.

This issue comes to the fore when more is made of the risk assessment than is appropriate. For example, when the qualitative identification of cancer hazard is interpreted as “at any dose” rather than “at some dose” or when the plausible upper bound becomes an absolute prediction of risk, the user of the assessment has strayed beyond the bounds of the science. This is not to say that, as risk assessors, we will never be able

to provide the desired tools. In science, however, pro- gress comes slowly. Assessments based on model com- pounds and scientific inference are offered reluctantly for use in chemical-specific situations. Validating new methodologies and flagging data gaps means additional data collection. In the meantime, risk managers, legis- lators, and the public grow impatient.

As we evolve, the solution is not to move away from risk assessment but to proceed cautiously, case-by-case, and to incorporate more scientific judgment into the process rather than legislate it out. The reward for this approach will be an incentive for generating data, the development of better approaches for estimating hazard and risk at environmentally relevant levels, and a scien- tifically sound contribution to the solution for risk man- agement problems. The punishment for misapplication will be a lack of confidence in risk-based approaches for regulatory decision making, a poor application of limited resources in solving environmental problems, and, ultimately, the removal of the input of health and environmental scientists from the decision-making process.

Kd William H. Farland, ucriny direcror uf rhr Ofice of Heulrh urid Environniorrul Assessmenr, Office of Resmrch nnrl Developmmr , Environmenrol Prorwtio,~ Ayency in Wushinjiron, D . C. , w m formerly dirrcror $rhe ujienc? :s Curcinoyen A.s.se.ssmem Group und is n charm mrmhrw ofrhr EPA’s Risk Assessmm Forum

4 Environ. Sci. Technol.. Vol. 22. NO. 1 . 1988 This arlicle not subject to U.S. Copyright. Published 1987 American Chemical Society