EXPEDITED CANCER POTENCY VALUE AND NO SIGNIFICANT RISK LEVEL (NSRL) FOR THE PROPOSITION 65 CARCINOGEN FUMONISIN B1 October 2009 Reproductive and Cancer Hazard Assessment Branch Office of Environmental Health Hazard Assessment (OEHHA) California Environmental Protection Agency SUMMARY OF FINDINGS

The cancer potency was estimated for fumonisin B1 using an expedited method. The dose-response data used in the analysis was generated by the National Toxicology Program ([NTP], 2001a; b) and summarized by Gold and colleagues (Gold & Zeiger, 1997; Gold, 2007) in the Carcinogenic Potency Database (CPDB). The expedited method represents the first level of a three-tiered risk assessment procedure currently in place for development of cancer potencies and Proposition 65 “No Significant Risk Levels” (NSRLs) and has been shown to produce reliable potency values (OEHHA, 1992; Hoover et al., 1995). Values generated using the expedited method may be reevaluated if scientific considerations indicate that more detailed analysis associated with a conventional risk assessment is warranted. Under the expedited method, the upper 95 percent confidence bound on the linear term of the multistage model fit to cancer dose response data is taken as the cancer potency estimate. The derivation takes into account species differences and length of the bioassay. The Proposition 65 NSRL is defined in regulation as the daily level posing a 10 lifetime risk of cancer. The cancer potency estimate and the corresponding NSRL for fumonisin B1 are given in Table 1.