Spec. Issue 2006 - Article Summary

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Cancerous contradictions: The mis-regulation of human carcinogens based on animal data

Andrew Knight1, Jarrod Bailey2 and Jonathan Balcombe3
1Animal Consultants International, London, UK; 2Faculty of Medical Sciences, University of Newcastle upon Tyne, UK; 3Physicians Committee for Responsible Medicine, Washington DC, USA
The regulation of human exposures to potential carcinogens constitutes society’s most important use of animal carcinogenicity data. However, for environmental contaminants of greatest U.S. concern, we found that in most cases (58.1%; 93/160) the U.S. Environmental Protection Agency (EPA) considered the animal data inadequate to support a classification of probable human carcinogen or non-carcinogen. The World Health Organisation’s International Agency for Research on Cancer (IARC) is a leading international authority on carcinogenicity assessments. For chemicals lacking human exposure data (the great majority), IARC classifications of identical chemicals were significantly more conservative than EPA classifications (p<0.0001), indicating that: (i) the EPA is over-reliant on animal carcinogenicity data, (ii) as a result, it tends to over-predict carcinogenic risk, and (iii) the true predictivity for human carcinogenicity of animal data is even poorer than indicated by EPA figures alone. EPA policy erroneously assuming that tumours in animals are indicative of human carcinogenicity is implicated as the greatest source of these errors.

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