[Federal Register Volume 62, Number 171 (Thursday, September 4, 1997)]
[Notices]
[Page 46751]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-23381]


-----------------------------------------------------------------------

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Public Health Service


National Toxicology Program; Availability of Technical Report on 
Toxicology and Carcinogenesis Studies of 1-Trans-Delta<SUP>9</SUP>-
Tetrahydrocannabinol

    The HHS' National Toxicology Program announces the availability of 
the NTP Technical Report on the toxicology and carcinogenesis studies 
of 1-trans-delta<SUP>9</SUP>-tetrahydrocannabinol which is a major 
psychoactive component of marijuana and a widely used Schedule I 
substance.
    Toxicology and carcinogenicity studies were conducted by 
administering 1-trans-delta<SUP>9</SUP>-tetrahydrocannabinol (THC) in 
corn oil to groups of 62 vehicle control male rats, 60 low-dose male 
rats, 70 mid- and high-dose male rats, and 60 female rats at doses of 
0, 12.5, 25, or 50 mg THC/kg body weight by gavage for 104 to 105 
weeks. Groups of 62 vehicle control male mice, 60 low-dose male mice, 
61 mid-dose male mice, and 60 high-dose male mice and 60 female mice 
were administered 0, 125, 250, or 500 mg THC/kg body weight in corn oil 
by gavage for 104 to 105 weeks (males) or 105 to 106 weeks (females).
    Under the conditions of these 2-year gavage studies, there was no 
evidence of carcinogenic activity \1\ of 1-trans-delta<SUP>9</SUP>-
tetrahydrocannabinol in male or female F344/N rats administered 12.5, 
25, or 50 mg/kg. There was equivocal evidence of carcinogenic activity 
of THC in male and female B6C3F1 mice based on the increased incidences 
of thyroid gland follicular cell adenomas in 125 mg/kg groups.
---------------------------------------------------------------------------

    \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'').
---------------------------------------------------------------------------

    Increased incidences of thyroid gland follicular cell hyperplasia 
occurred in male and female mice, and increased incidences of 
hyperplasia and ulcers of the forestomach were observed in male mice.
    The incidences of mammary gland fibroadenomas and uterine stromal 
polyps were decreased in dosed groups of female rats, as were the 
incidences of pancreatic adenomas, pituitary gland adenomas, and 
interstitial cell adenomas of the testis in dosed male rats and liver 
neoplasms in dosed mice. These decreases were likely related to lower 
body weights in dosed animals.
    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 1-Trans-
Delta<SUP>9</SUP>-Tetrahydrocannabinol (CAS No. 1972-08-3) (TR-446) are 
available from Central Data Management, NIEHS, MD E1-02, PO Box 12233, 
Research Triangle Park, NC 27709; telephone (919) 541-3419.

    Dated: August 14, 1997.
Samuel H. Wilson,
NIEHS Deputy Director.
[FR Doc. 97-23381 Filed 9-3-97; 8:45 am]
BILLING CODE 4140-01-M