[Federal Register Volume 59, Number 137 (Tuesday, July 19, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-17450]


[[Page Unknown]]

[Federal Register: July 19, 1994]


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DEPARTMENT OF HEALTH AND HUMAN SERVICES
 

National Toxicology Program; Availability of Technical Report on 
Toxicology and Carcinogenesis Studies of Manganese (II) Sulfate 
Monohydrate

    The HHS' National Toxicology Program announces the availability of 
the NTP Technical Report on the toxicology and carcinogenesis studies 
of manganese sulfate monohydrate. Manganese is the 12th most abundant 
element in the earth's crust. The base metal does not occur naturally, 
but is a component of more than 100 minerals, including sulfides, 
oxides, carbonates, silicates, phosphates, and borates. In addition to 
occurring in foods and drinking water, manganese occurs in the 
atmosphere from dust, volcanic activity, forest fires, and industrial 
emissions. Manganese (II) sulfate monohydrate was chosen for study 
because of its stability, solubility, and availability.
    Toxicology and carcinogenicity studies were conducted by 
administering manganese (II) sulfate monohydrate (97% pure) in feed to 
groups of 70 male and 70 female F344/N rats and B6C31 mice at 
doses of 1, 1,500, 5,000, or 15,000 ppm for up to 2 years.
    Under the conditions of these 2-year feed studies, there was no 
evidence of carcinogenic activity* of manganese (II) sulfate 
monohydrate in male or female F344/N rats receiving 1,500, 5,000, or 
15,000 ppm. There was equivocal evidence of carcinogenic activity of 
manganese (II) sulfate monohydrate in male and female B6C3F1 mice, 
based on the marginally increased incidences of thyroid gland 
follicular cell adenoma and the significantly increased incidences of 
follicular cell hyperplasia.
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    *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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    The ingestion of diets containing manganese (II) sulfate 
monohydrate was associated with an increased severity of nephropathy in 
male rats, focal squamous hyperplasia of the forestomach in male and 
female mice, and ulcers and inflammation of the forestomach in male 
mice. These studies were not designed to assess any neurotoxicity that 
might have been expected with chronic exposure to sufficiently high 
doses of manganese.
    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 Manganese (II) 
Sulfate Monohydrate (CAS No. 10034-96-5) in F344/N Rats and B6C3F1 
Mice (Feed Studies) (TR-428) 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: July 13, 1994.
Kenneth Olden,
Director, National Toxicology Program.
[FR Doc. 94-17450 Filed 7-18-94; 8:45 am]
BILLING CODE 4140-01-M