[Federal Register Volume 60, Number 130 (Friday, July 7, 1995)]
[Notices]
[Pages 35411-35412]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-16675]



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DEPARTMENT OF HEALTH AND HUMAN SERVICES

National Toxicology Program; Availability of Technical Report on 
Toxicology and Carcinogenesis Studies of 4,4'-Thiobis (6-t-Butyl-m-
Cresol)

    The HHS' National Toxicology Program announces the availability of 
the NTP Technical Report on the toxicology and carcinogenesis studies 
of 4,4'-thiobis (6-t-butyl-m-cresol), which is used in the rubber and 
plastics industries as an antioxidant for polyolefins, polyethylenes, 
polypropylenes, natural rubber and latex. It is approved by FDA as a 
constituent of high-pressure polyethylene packaging for foodstuffs, 
excluding fats, and as a component of polyolefin film packaging in 
contact with meat or meat food products.
    Toxicology and carcinogenicity studies were conducted by 
administering 4,4'-thiobis (6-t-butyl-m-cresol) in feed to groups of 
115 male and 75 female F344/N rats at doses of 0, 500, 1,000, or 2,500 
ppm and to groups of 80 B6C3F1 mice of each sex at doses of 0, 
250, 500, or 1,000 ppm for 2 years.
    Under the conditions of these 2-year feed studies, there was no 
evidence of carcinogenic activity 1 of 4,4'-thiobis (6-t-butyl-m-
cresol) in male or female F344/N rats administered 500, 1,000, or 2,500 
ppm or in male or female B6C3F1 mice administered 250, 500, or 
1,000 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 TBBC included: 
Kupffer cell 

[[Page 35412]]
hypertrophy, cytoplasmic vacuolization, and mixed cell foci in the 
liver of male and female rats, fatty change in the liver of female 
rats, and an increase in the severity of nephropathy in the kidney of 
female rats. In addition, decreased incidences of fibroadenoma, 
adenoma, or carcinoma (combined) were observed in the mammary gland of 
female rats. Decreases also occurred in the incidences of fatty change, 
clear cell foci, and adenoma or carcinoma (combined) in the liver of 
male 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 4,4'-Thiobis (6-
t-Butyl-m-Cresol) (CAS No. 96-69-5) (TR-435) are available without 
charge from Central Data Management, NIEHS, MD A0-01, P.O. Box 12233, 
Research Triangle Park, NC 27709; telephone (919) 541-3419.

    Dated: May 30, 1995.
Kenneth Olden,
Director, National Toxicology Program.
[FR Doc. 95-16675 Filed 7-6-95; 8:45 am]
BILLING CODE 4140-01-P