[Federal Register Volume 60, Number 130 (Friday, July 7, 1995)]
[Notices]
[Page 35411]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-16676]



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DEPARTMENT OF HEALTH AND HUMAN SERVICES

National Toxicology Program; Availability of Technical Report on 
Toxicology and Carcinogenesis Studies of Tricresyl Phosphate

    The HHS' National Toxicology Program announces the availability of 
the NTP Technical Report on the toxicology and carcinogenesis studies 
of tricresyl phosphate which is an organophosphate plasticizer 
primarily used as a vinyl plasticizer in the manufacture of vinyl 
plastics for automotive interiors and as a fire-retardant and anti-wear 
additive to industrial lubricants such as hydraulic fluids, extreme 
pressure fluids, cutting oils, machine oils, automotive transmission 
fluids, and certain cooling lubricants.
    Toxicology and carcinogenicity studies were conducted by 
administering tricresyl phosphate in feed to groups of 95 F344/N rats 
of each sex at doses 0, 75, 150, or 300 ppm for 2 years. An additional 
group of 95 F344/N rats of each sex were given a dose of 600 ppm for 22 
weeks and then received only control feed. After 3, 9, and 15 months of 
chemical exposure, up to 15 F344/N rats of each sex per group were 
evaluated for forelimb and hindlimb grip strength, then necropsied and 
evaluated for histopathologic lesions. Groups of 95 B6C3F2 mice of 
each sex were fed diets at doses 0, 60, 125, or 250 ppm for 2 years. 
After 3, 9, and 15 months of chemical exposure, up to 15 of each sex 
per group were evaluated for forelimb and hindlimb grip strength, then 
necropsied and evaluated for histopathologic lesions. An additional 
group of 10 F344/N rats and B6C3F1 mice of each sex received 
tricresyl phosphate in corn oil by gavage at doses of 0, 360, 730, 
1,450, 2,900, or 5,800 mg/kg body weight for 16 days. Groups of 10 
F344/N rats and B6C3F1 mice of each sex received tricresyl 
phosphate in corn oil by gavage at doses of 0, 50, 100, 200, 400, or 
800 mg/kg body weight for 13 weeks.
    Under the conditions of these 2-year feed studies, there was no 
evidence of carcinogenic activity 1 of tricresyl phosphate in male 
or female F344/N rats that received 75, 150, or 300 ppm. There was no 
evidence of carcinogenic activity of tricresyl phosphate in male or 
female B6C3F1 mice that received 60, 125, or 250 ppm.

    \1\ 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'').
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    Nonneoplastic lesions associated with exposure to tricresyl 
phosphate included cytoplasmic vacuolization of the adrenal cortex and 
ovarian interstitial cell hyperplasia in female rats, increased 
incidences of clear cell focus, fatty change, and ceroid pigmentation 
of the liver in male mice, and increased severity of ceroid 
pigmentation of the adrenal cortex in female mice.
    Questions or comments about the Technical Report should be directed 
to Central Data Management at PO Box 12233, Research Triangle Park, NC 
27709 or telephone (919) 541-3419.
    Copies of Toxicology and Carcinogenesis Studies of Tricresyl 
Phosphate (CAS No. 1330-78-5) (TR-433) are available without charge 
from Central Data Management, NIEHS, MD A0-01, PO Box 12233, Research 
Triangle Park, NC 27709; telephone (919) 541-3419.

    Dated: June 14, 1995.
Kenneth Olden,
Director, National Toxicology Program.
[FR Doc. 95-16676 Filed 7-6-95; 8:45 am]
BILLING CODE 4140-01-P