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.1!,. • - - • _ my ; y=h <br /> ::rth the health effects rnforrnation o-velnpGO Unger the'R11CL process Thus <br /> primary I1CLs are not nece_sarily a reliatfle indicator of protection of an <br /> ambient water resource and should not be relied upon as water quality goals in <br /> cleanup situations. <br /> Drsrussion <br /> Chloroform is a potential human carcinogen. The International Agency for <br /> Research on Cancer (IARC) evaluates the strength of the evidence for <br /> carcinogenicity of substances and publishes those evaluations in their <br /> "monographs". The IARC defines chloroform as a chemical "for which there is <br /> sufficient evidence of carcinogenicity in experimental animals." 2 For <br /> comparison, the IARC does not find that such "sufficient evidence" exists for <br /> trichloroethylene (TCE). In a 1980 IARC publication, TCE was categorized as a <br /> chemical "with very strong evidence for carcinogenicity in one species and no <br /> evidence in a second species." 3 The same publication categorized chloroform <br /> as a chemical "with very strong evidence (to an unusual degree and/or in <br /> multiple experiments) for carcinogenicity in two animal species." 3 It is clear <br /> that the cancer risk data for chloroform is more reliable as an indicator of <br /> potential human carcinogenicity than that for TCE. <br /> In 1980, the U.S. EPA published a document entitled Ambient Water Quality <br /> Criteria for Chloroform 1, in which the following criteria for human health <br /> protection were provided: <br /> "For the maximum protection of human health from the potential <br /> carcinogenic effects due to exposure of chloroform through ingestion of <br /> contaminated water and contaminated aquatic organisms, the ambient <br /> water concentrations should be zero based on the non-threshold <br /> assumption for this chemical. However, zero level may not be <br /> attainable at the present time. Therefore, the levels which may result <br /> in incremental increase of cancer risk over the lifetime are estimated <br /> at 10-5, 10-6, and 10-7. The corresponding recommended criteria are <br /> 1.90 pg/l, 0.19 pg/l, and 0.019 pg/l, respectively." <br /> EPA has also established a 10-6 cancer risk level for TCE of 4.5 pg/14 DHS <br /> endorsed this value by promulgating their "action level" for TCE at 5 ug/1 5, <br /> and is using this value in ground water cleanup cases. EPA more recently <br /> establish a drinking water RMCL of "zero" for TCE (federal statutes mandate <br />