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CANCER RISK ASSESSMENT FOR CHLOROFORM
Citation:
Chiu, N., O. Zavaleta, A. Chiu, C. Chen, AND J. Blancato. CANCER RISK ASSESSMENT FOR CHLOROFORM. The Toxicologist 30(1pt2):587, (1996).
Description:
Chloroform is a common chlorination by-product in drinking water. EPA has regulated chloroform as a probable human carcinogen under the Safe Drinking Water Act. The cancer risk estimate via ingestion was based on the 1985 Jorgenson study identifying kidney tumors in male Osborne Mendel rats. This assessment researched the correlation between certain direct(e.g.necrosis)and indirect(e.g.cell proliferation)parameters of cytotoxicity and tumorigenicity reported by available studies. Variables such as species,sex,strain,target tissue,dose level,dose vehicle, and exposure duration are specified. There is a good correlation between certain cytotoxic effects of chloroform and the occurrence of liver tumor in female B6C3F1 mice(via DW and corn oil gavage). It appears that there is little or no correlation between certain cytotoxic effects and tumorigenicity in:1) liver of male Fischer-344 rats(DW),2)liver&kidney of Fischer-344 male rats(inhalation),3)kidney of male B6C3F1 mice (corn oil gavage), and 4)kidney of male Osborne-Mendel rat(DW and corn oil gavage). Cancer risk in the kidney was compared using the data from male rats administered with chloroform by corn oil gavage(NC1,1976)or by drinking water (Jorgenson et.al.1985)using LMS model. Because of concern over the possible effects of unequal survival rates in animals in different dose groups, the data for these studies were also modeled using time-to-tumor method. There are no significant differences in kidney cancer risks using data of rats exposed to chloroform by corn oil gavage or by drinking water.