[Federal Register Volume 62, Number 112 (Wednesday, June 11, 1997)]
[Notices]
[Page 31837]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-15298]


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DEPARTMENT OF HEALTH AND HUMAN SERVICES

Public Health Service


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

    The HHS' National Toxicology Program announces the availability of 
the NTP Technical Report on the toxicology and carcinogenesis studies 
of phenolphthalein which is used as a laboratory reagent and acid-base 
indicator and in over-the-counter laxative preparations. The results of 
these studies were previously released in draft form prior to a public 
peer review in December, 1995.
    Toxicology and carcinogenicity studies were conducted by 
administrating phenolphthalein to groups of 50 F344/N rats for 2 years 
and to B6C3F1 mice at exposures of 0, 3000, 6000 or 12,000 
ppm in the feed for 2 years (equivalent to average daily doses of 
approximately 300, 600 or 1200 mg phenolphthalein/kg body weight to 
males and 400, 800 or 1000 mg/kg to females).
    Under the conditions of these 2-year feed studies, there was clear 
evidence of carcinogenic activity \1\ of phenolphthalein in male F344/N 
rats based on markedly increased incidences of benign pheochromocytomas 
of the adrenal medulla and of renal tubule adenomas and adenomas or 
carcinomas (combined). There was some evidence of carcinogenic activity 
of phenolphthalein in female F344/N rats based on the increased 
incidences of benign pheochromocytomas of the adrenal medulla in the 
12,000 ppm group and of benign or malignant pheochromocytomas 
(combined) in the 12,000 and 25,000 ppm groups. There was clear 
evidence of carinogenic activity of phenolphthalein in male 
B6C3F1 mice based on increased incidences of histiocytic 
sarcomas and of malignant lymphomas of thymic origin. there was clear 
evidence of carcinogenic activity of phenolphthalein in female 
B6C3F1 mice based on increased incidences of histiocytic 
sarcomas, malignant lymphomas of all types, lymphomas of thymic origin, 
and benign sex-cord stromal tumors of the ovary.
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    \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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    Exposure of rats to phenophthalein in feed for 2 years resulted in 
increased incidences of focal hyperplasia of the adrenal medulla in 
males and in increased incidences and/or severity of nephropathy of the 
kidney in males and females. Exposure of mice to phenolphthalein in 
feed for 2 years resulted in increased incidences of atypical 
hyperplasia of the thymus in males and females, degeneration of the 
germinal epithelium of the testis in males, and ovarian hyperplasia in 
females.
    Exposure of mice to phenolphthalein in feed for 2 years resulted in 
decreased incidences of hepatocellular neoplasms and nonneoplastic 
lesions in males and females.
    Questions or comments about the Technical Report should be directed 
to Central Data Management at P.O. Box 12233, Research Triangle Park, 
NC 27709-2233.
    Copies of Toxicology and Carcinogenesis Studies of Phenolphthalein 
(CAS No. 77-09-8) (TR-465) are available from Central Data Management, 
NIEHS, MD E1-02, P.O. Box 12233, Research Triangle Park, NC 27709-2233; 
telephone (919) 541-3419.

    Dated: May 28, 1997.
Kenneth Olden,
Director, National Toxicology Program.
[FR Doc. 97-15298 Filed 6-10-97; 8:45 am]
BILLING CODE 4140-01-M