National Toxicology Program

DEPARTMENT OF HEALTH AND HUMAN SERVICES
Public Health Service

National Toxicology Program (NTP); Availability of Technical Report on Toxicology and Carcinogenesis Studies of Diethylphthalate with Dermal Initiation/Promotion Study of Diethylphthalate and Dimethylphthalate

The HHS' National Toxicology Program announces the availability of the NTP Technical Report on the toxicology and carcinogenesis studies of Diethylphthalate. Diethylphthalate and Dimethylphthalate are used as phthalte plasticizers in an extensive array of products.

Toxicology and carcinogenicity studies were conducted by dermal administration of diethylphthalate to groups of 60 F344/N rats of each sex at doses of 0, 100, or 300 µL and to groups of 60 B6C3F1 mice of each sex at doses of 0, 7.5, 15, or 30 µL. Neat chemical was applied to rats for 5 days per week for 103 weeks and up to 10 animals per group were evaluated after 15 months. Mice received doses in 100 µL of acetone for 5 days per week for 103 weeks with a 1 week recovery period, and up to 10 animals per group were evaluated after 15 months.

An additional group of 50 male Swiss (CD-1®) mice were dosed dermally with diethylphthalate or dimethylphthalate to study their effect as initiators and promoters. They were tested as initiators with and without 12-O-tetradecanoylphorbol and they were tested as promoters with and without the known skin tumor initiator 7,12-dimethylbenzanthrancene.

Under the conditions of these 2-year dermal studies, there was no evidence of carcinogenic activity* of diethylphthalate in male or female F344/N rats receiving 100 or 300 µL. There was equivocal evidence of carcinogenic activity of diethylphthalate in male and female B6C3F1 mice based on increased incidences of hepatocellular neoplasms, primarily adenomas.

In the initiation/promotion model, there was no evidence of initiating or promoting activity of diethylphthalate or dimethylphthalate in male Swiss (CD-1®) mice.

Questions or comments about the Technical Report should be directed to Central Data Management at P.O. Box 12233, Research Triangle Park, NC 27709 or telephone (919) 541-3419.

Copies of Toxicology and Carcinogenesis Studies of Diethylphthalate/Dimethylphthalate (CAS Nos. 84-66-2 and 131-11-3) (TR-429) are available without charge from Central Data Management, NIEHS, MD E1-02, P.O. Box 12233, Research Triangle Park, NC 27709; telephone (919) 541-3419 or send e-mail to CDM@niehs.nih.gov.

Dated: March 27, 1996

 
________________________________
Kenneth Olden, Ph.D.
Director
National Toxicology Program

[Billing Code 4140-01]

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*The NTP uses five categories of evidence of carcinogenic activity observed in each animal study: two categories for positive results ("clear evidence" and "some evidence"), one category for uncertain findings ("equivocal evidence"), one category for no observable effect ("no evidence"), and one category for studies that cannot be evaluated because of major flaws ("inadequate study").