National Toxicology Program, carcinogen risk

Finally, a recently published draft report of a National Toxicology Program study found DOP (or DEHP as it is referred to in toxicology studies) to be carcinogenic to certain strains of mice and rats when fed at very high levels in the diet for the lifetime of the test animals. It may be a number of years before the mechanism of the induced carcinogenic effects can be understood, and a realistic assessment of any risk to man can be made. The final version of the draft report is expected to issue in February, 1981. 

Bucher JR, Portier C. Human carcinogenic risk evaluation. Part V The National Toxicology Program vision of assessing the human carcinogenic hazard of chemicals. Toxicol Sci 2004 82 363-6. 

The US Environmental Protection Agency has classified isophorone as a possible human carcinogen. The National Toxicology Program tested isophorone for evidence of carcinogenicity and found the following male rat - some evidence female rat - no evidence male mice - equivocal evidence female mice - no evidence. European Risk Phrases suggest there is possible risk of irreversible effects upon repeated overexposure. 

The second common type of design is the original National Toxicology Program (NTP) bioassay. The announced objective of these studies was detection of moderate to strong carcinogens, although the results have also been used in attempts at risk assessment. 

It is particularly true with respect to the assessment of carcinogenic risks that we have had to place virtually complete reliance upon extrapolation from animal tests. This has resulted in the restriction of use or removal from the marketplace of several chemical substances including pesticides - such as DDT, Aldrin, Dieldrin, Chlordane and Heptachlor. Other pesticides and chemicals already in use have also been found to be carcinogenic to one or more animal species in the National Cancer Institute testing program - now part of the National Toxicology Program. 

For NTP carcinogens, see US Department of Flealth and Fluman Services, Public Flealth Service, National Toxicology Program. 2005. Report on Carcinogens, Eleventh Edition (http //ntp.niehs.nih.gov/ntp/roc/toc11. html—accessed February 12,2007). For reproductive/developmental toxicants see the NTP Center for the Evaluation of Risks to Fluman Reproduction (http //cerhr.niehs.nih.gov/). 

In order to provide additional information for the risk assessment, the Committee performed benchmark dose (BMD) modelling using the carcinogenicity data on ochratoxin A from the rat bioassay performed by the NTP (National Toxicology Program, 1989). The occurrence of combined adenomas and carcinomas in the kidneys of the male rats (Table 2), as the most sensitive sex and species for kidney carcinogenicity of ochratoxin A, was considered the most appropriate data for modelling. 

NTP (National Toxicology Program). 1982. Carcinogenesis bioassay of di-(2-ethylhexyl) phthalate (CAS No. 117-81-7) in F344rats and B6C3F, mice (feed study). NTP Tech. Rep. Ser. TRNo. 217, 1982. Some industrial Chemicals, lARC monographs on the Evaluation of Carcinogenic risks to humans, Vol 77, February 2000, p 15-22. 

Health risks associated with PFASs are not yet well established however the assessment of potential risks is the subject of numerous studies [151—153]. Knovm or suspected risks include chronic toxicity, carcinogenic activity, endocrine effects, and bioaccumulation—biomagnification. PFASs are included in the National Health and Nutrition Examination Survey (NHANES) conducted by the Centers for Disease Control and Prevention (CDC) [154], and the National Toxicology Program has included various PFASs in their assessment of toxicity, carcinogenicity, and persistence in human blood [155]. 

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