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The following HTML text is provided to enhance online readability. Many aspects of typography translate only awkwardly to HTML. Please use the page image as the authoritative form to ensure accuracy. CancerThere are inadequate data to characterize the carcinogenic risk from exposure to zinc borate, zinc oxide, or boric acid from any route of exposure. RECOMMENDATIONS FROM OTHER ORGANIZATIONSThe U.S. Environmental Protection Agency (EPA), as detailed in the Integrated Risk Information System (IRIS), has established an oral RfD for boron of 0.09 mg/kg-d (EPA 1999). The risk assessment for boron has not been updated since 1989. However, that RfD is currently under review and a revised RfD is expected in the yr 2000 (Fed. Regist. 63 (December 10, 1998):68353–68364). The International Programme on Chemical Safety (IPCS) has an Environmental Health Criteria document (IPCS 1998) on boron in which a tolerable intake for boron is set at 0.4 mg boron/kg-d based on recent reproductive and developmental data. The Agency for Toxic Substances and Disease Registry (ATSDR) has published toxicological profiles for zinc and boron. An oral minimal risk level (MRL) of 0.3 mg Zn/kg-d for zinc was based on hematological effects (ATSDR 1994). ATSDR lists an oral MRL for boron of 0.01 mg boron/kg-d based on developmental effects (ATSDR 1992). The National Research Council (NRC) has established a recommended dietary allowance (RDA) for zinc of 12–15 mg/d (0.17–0.21 mg/kg-d of zinc for a 70-kg person (NRC 1980). The Occupational Safety and Health Administration (OSHA) and the American Conference of Government Industrial Hygienists (ACGIH) considered the toxicity from zinc borate and its components in the workplace to be due to “Particulate Not Otherwise Classified” or “Nuisance Dust.” Therefore, the OSHA permissible exposure level is 15 mg/m3 for total dust and 5 mg/m3 for respirable dust, and the ACGIH Threshold Limit Value for zinc oxide dust is 10 mg/m3 (ACGIH 1999). DATA GAPS AND RESEARCH NEEDSThere are little toxicity data available for zinc borate. Once in the body, zinc borate readily breaks down to zinc oxide and boric acid. There are no chronic studies investigating the carcinogenicity of zinc oxide and boric acid. There are
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