Note: This document is superseded by DHHS (NIOSH) Publication No. 80-142, OSHA/NIOSH Health Hazard Alert2-Nitropropane (2-NP) |
This Bulletin provides the results of this animal study along with other pertinent data, their implications for occupational healthy and precautions for handling 2-nitropropane in the workplace.
Synonyms for 2-nitropropane include dimethylnitromethane, isonitropropane, nitroisopropane, and 2-NP. Trade names under which 2-nitropropane is marketed include NiPar S-20TM (commercial grade 2-nitropropane) and NiPar S-30TM (mixtures of 1- and 2-nitropropane). 2-Nitropropane (in concentrations ranging from approximately 5 to 25 percent) is used in a number of solvent systems to contribute desirable properties such as improved drying time, more complete solvent release, better flow and film integrity, retardation of blushing, greater wetting ability, improved electrostatic spraying, and increased pigment dispersion.
The sole known domestic producer of 2-nitropropane has been Commercial Solvents Corporation (recently acquired by International Minerals and Chemical Corporation, IMC). 2-Nitropropane has been manufactured at their Sterlington, Louisiana plant since 1955, and in a pilot plant in Peoria, Illinois from 1940 to 1955. Of the estimated thirty million pounds of Z-nitropropane produced annually, twelve million pounds per year are sold domestically; the remainder is either used internally at IMC or exported.
Although certain shortcomings do exist in the conduct of this study,* the experiment is sufficient to merit the concern of the occupational health community. NIOSH has been advised that further investigation of the toxicity of 2-nitropropane has recently begun (April, 1977) under the sponsorship of the IMC Chemical Group, Inc.
The effects of 2-nitropropane inhalation in laboratory animals have also been studied by Treon and Dutra (Arch. Ind. Hyg. and Occ. Med., 5:52, 1952). Five species of laboratory animals (2 animals of each species per exposure level) were exposed to various concentrations of 2-nitropropane. Acute exposures ranged up to 9000 ppm for short time periods (as low as one hour), while chronic exposure levels ranged down to 83 ppm 2-nitropropane for as long as 26 weeks. Treon and Dutra reported no histologic changes in the monkeys, rabbits, guinea pigs and rats exposed to 328 ppm or less regardless of exposure time.** However, both cats died within 17 days of exposure to 328 ppm and had severe liver damage and slight to moderate damage to the kidney and heart.
There are a number of published reports concerning acute health effects of occupational exposure to 2-nitropropane. One report of two workers attributes the death of one and liver damage in both workers to high level exposure to 2-nitropropane while painting the inside of a tank (Gaultier, M., et al., Arch. d. Mal. Prof. 25:425, 1964). Another paper relates that continual exposure to concentrations of 20 to 45 ppm 2-nitropropane caused workers in one plant to experience nausea, vomiting diarrhea anorexia, and severe headaches (Skinner, J.B., Ind. Med. 16:441, 1947). A third report indicates that workers exposed to from 165 to 445 ppm mixed 1-and 2- nitropropane also experienced nausea, dizziness, headaches and diarrhea (Documentation of Threshold Limit Values, American Conference of Governmental Industrial Hygienists, 1971). In addition Williams, et. al., (New Eng. J. of Med., 291:1256, 1974) reported an excess of toxic hepatitis among construction workers applying epoxy resins to the walls of a nuclear power plant. Although the hepatitis in this case was attributed to exposure to a known hepatotoxin, p,p'-methylenedianiline 4,4'-diaminodiphenylmethane), these men were also observed to have used 2-nitropropane to remove the hardened resin from their skin.
The current Occupational Safety and Health Administration (OSHA) standard for occupational exposure to 2-nitropropane is 25 ppm. However, in light of the new information generated by the Huntingdon study, and while the carcinogenic potential of 2-nitropropane is being further evaluated NIOSH believes that it would be prudent to handle 2-nitropropane in the workplace as if it were a human carcinogen. The attached interim recommended industrial hygiene practices were developed by NIOSH to help reduce occupational exposure to 2-nitropropane.
[signature] John F. Finklea, M.D. Director |
b. Wherever possible the operations utilizing 2-nitropropane should be enclosed (with appropriate ventilation) to reduce exposures to the operators and others in the area.
B. Medical Monitoring. employees with a potential exposure to 2-nitropropane should be placed under a medical monitoring program including history and medical examinations with specific emphasis on liver function tests.
C. Substitution. substitution of a solvent that does not contain 2-nitropropane is another possible control measure. Caution should be exercised in selecting a substitute for 2-nitropropane, giving full consideration to the possible toxic effects of the substitute.
**On subsequent examination by a NIOSH pathologist in March 1977, liver sections from two rats in this study which were exposed to about 300 ppm 2-nitropropane for seventeen exposures (7 hours each) showed clear cell foci. These and similar lesions are frequently seen prior to the development of hepatocellular carcinoma in rats exposed to known hepatic carcinogens. The lesions observed in the Treon and Dutra study are similar to those found in the liver sections of the rats in the Huntingdon study which were sacrificed after three months exposure to 207 ppm 2-nitropropane. [return to text]
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