Knight A, Bailey J, Balcombe J. Animal carcinogenicity studies: 1 poor human predictivity. Alternatives to Laboratory Animals 2006; 34(1):19-27. Download (123 kb).

 

ABSTRACT
The regulation of human exposure to potentially carcinogenic chemicals constitutes society’s most important use of animal carcinogenicity data. Environmental contaminants of greatest concern within the USA are listed in the Environmental Protection Agency’s (EPA’s) Integrated Risk Information System (IRIS) chemicals database. However, of the 160 IRIS chemicals lacking even limited human exposure data but possessing animal data that had received a human carcinogenicity assessment by 1 January 2004, we found that in most cases (58.1%; 93/160), the EPA considered animal carcinogenicity data inadequate to support a classification of probable human carcinogen or non-carcinogen. For the 128 chemicals with human or animal data also assessed by the World Health Organisation’s International Agency for Research on Cancer (IARC), human carcinogenicity classifications were compatible with EPA classifications only for those 17 having at least limited human data (p = 0.5896). For those 111 primarily reliant on animal data, the EPA was much more likely than the IARC to assign carcinogenicity classifications indicative of greater human risk (p < 0.0001). The IARC is a leading international authority on carcinogenicity assessments, and its significantly different human carcinogenicity classifications of identical chemicals indicate that: 1) in the absence of significant human data, the EPA is over-reliant on animal carcinogenicity data; 2) as a result, the EPA tends to over-predict carcinogenic risk; and 3) the true predictivity for human carcinogenicity of animal data is even poorer than is indicated by EPA figures alone. The EPA policy of erroneously assuming that tumours in animals are indicative of human carcinogenicity is implicated as a primary cause of these errors.          

 

Veterinarian Andrew Knight BSc., BVMS, CertAW, MRCVS, is the Founder, Director and web designer of Animal Consultants International. He is an expert on humane alternatives to harmful animal use in education, animal experimentation, and vegetarian companion animal diets. An active animal advocate since 1995, he has extensive public speaking, media, research and writing experience.

 

Biologist Jonathan Balcombe, Ph.D. (Ethology), author of The Use of Animals in Higher Education, a forthcoming book on animal pleasure, and many scientific articles on humane education and animal behavior, promotes alternatives to animal use in research and education. Formerly an Associate Director with The Humane Society of the United States, he is currently a Research Consultant with the Physicians Committee for Responsible Medicine.