[Federal Register Volume 60, Number 130 (Friday, July 7, 1995)]
[Notices]
[Page 35412]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-16674]



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DEPARTMENT OF HEALTH AND HUMAN SERVICES

National Toxicology Program; Availability of Technical Report on 
Toxicology and Carcinogenesis Studies of Ozone and Ozone/NNK

    The HHS' National Toxicology Program announces the availability of 
the NTP Technical Report on the toxicology and carcinogenesis studies 
of ozone, the major oxidizing component in the type of air pollution 
known as a photochemical smog formed naturally in the stratosphere by 
photodissociation of oxygen. Ozone has also been used commercially as 
an effective disinfectant in the treatment of wastewater, as an odor 
control compound for waste odors and around sewage-treatment plants, 
and as a disinfectant in swimming pools. It is also used to bleach 
paper pulp and cotton fibers.
    Toxicology and carcinogenicity studies were conducted by 
administering ozone by inhalation to groups of 50 male and female F344/
N rats at doses 0, 0.12, 0.5, or 1.0 ppm for 6 hours per day, 5 days 
per week, for 105 weeks and 50 male and 50 female B6C3F1 mice at 
doses 0, 0.12, 0.5, or 1.0 ppm for 6 hours per day, 5 days per week, 
for 105 weeks. In addition, groups of male and female F344/N rats and 
B6C3F1 mice were exposed to 0, 0.5, or 1.0 ppm ozone for up to 125 
weeks, and groups of male F344/N rats were exposed to 0.5 ppm ozone 
along with a lung carcinogen, NNK, to determine if ozone had any 
promoting or cocarcinogenic effects.
    Under the conditions of these 2-year and lifetime inhalation 
studies, there was no evidence of carcinogenic activity 1 of ozone 
in male or female F344/N rats exposed to 0.12, 0.5, or 1.0 ppm. There 
was equivocal evidence of carcinogenic activity of ozone in male 
B6C3F1 mice based on increased incidences of alveolar/bronchiolar 
adenoma or carcinoma. There was some evidence of carcinogenic activity 
of ozone in female B6C3F1 mice based on increased incidences of 
alveolar/bronchiolar adenoma or carcinoma.

    \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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    There was no evidence that exposure to 0.5 ppm ozone enhanced the 
incidence of NNK-induced pulmonary neoplasms in male rats.
    Exposure of male and female rats to ozone for 2 years or 125 weeks 
was associated with goblet cell hyperplasia and squamous metaplasia in 
the nose, squamous metaplasia in the larynx, and metaplasia (extension 
of bronchial epithelium into the centriacinar alveolar ducts) and 
interstitial fibrosis in the lung. Exposure of male and female mice to 
ozone for 2 years or 130 weeks was associated with hyperplasia and 
squamous metaplasia in the nose and inflammation (histiocytic 
infiltration) and metaplasia (extension of bronchial epithelium into 
the centriacinar alveolar ducts) of the lung.
    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 Ozone (CAS No. 
10028-15-6) and Ozone /NNK (CAS No. 10028-15-6/64091-91-4) (TR-440) 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. 95-16674 Filed 7-6-95; 8:45 am]
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