IMPROVING THE REGULATION OF CARCINOGENS BY EXPEDITING CANCER POTENCY ESTIMATION

The statutory language of the Safe Drinking Water and Toxic Enforcemen t Act of 1986 (Proposition 65; California Health and Safety Code 25249 .5 et seq.) encourages rapid adoption of ''no significant risk levels' ' (NSRLs), intakes associated with estimated cancer risks of no more t han 1 in 100,000. Derivation of an NSRL for a carcinogen listed under Proposition 65 requires the development of a cancer potency value. Thi s paper discusses the methodology for the derivation of cancer potenci es using an expedited procedure, and provides potency estimates for a number of agents listed as carcinogens under Proposition 65. To derive expedited potency values, default risk assessment methods are applied to data sets selected from an extensive tabulation of animal cancer b ioassays according to criteria used by regulatory agencies. A subset o f these expedited values is compared to values previously developed by regulatory agencies using conventional quantitative risk assessment a nd found to be in good agreement. Specific regulatory activities which could be facilitated by adopting similar expedited procedures are ide ntified.