On September 17, 1976, the National Institute for Occupational Safety and Health (NIOSH) was informed by the National Science Foundation (NSF) that Dr. David H. Fine (Thermo Electron Corporation, Waltham, Massachusetts), one of its grantees, confirmed the presence of a nitrosamine, diethanolnitrosamine, in commercial cutting fluids produced by four randomly selected companies.
Historically, nitrosamines have been regarded as one of the most potent families of animal carcinogens. Although nitrosamines are suspected to be human carcinogens, their carcinogenic potential in man has not been proven.
In the past year, two developments have drawn attention to the issue of nitrosamines as an occupational health hazard. The first is the introduction of a new analytical method, thermal energy analysis (TEA), with a sensitivity for nitrosamines in the part per billion (ppb) range. The other development is the recognition of the potential for formation of nitrosamines in air and other non-acidic media by reaction of secondary and tertiary amines with nitrites or other oxides of nitrogen.
The formation of diethanolnitrosamine in cutting fluids was first postulated and reported by Zingmark and Rappe in Sweden (AMBIO, Vol, 5 No. 2, 80-81, 1976). They measured diethanolnitrosamine in a specifically formulated "grinding fluid" containing nitrite and triethanolazine. They concluded that the potential hazard of working with these types of products should not be underestimated. Dr. Fine's results of September 17, 1976, underscore the concern raised by Zingmark and Rappe. Dr. Fine initially reported finding from 400 to over 1,000 ppm diethanolnitrosamine in eight commercial cutting fluids produced by four different manufacturers. He has also provided NIOSH with results which indicate up to 3% diethanolnitrosamine in certain cutting fluids. In addition, Dr. Fine has reported a study conducted during an actual machining operation showing the presence of 1000 ppm diethanolnitrosamine. In the diluted cutting fluid prior to use, and 384 ppm after use. This finding strongly suggests that machine operators may be continuously exposed to nitrosamines.
Occupational exposure to cutting fluids, primarily among machine operators, has been studied for possible health effects. A recent published account by Decoufle (Ann. N.Y. Acad. Sci., 271:94-101, 1976) relates that a slight excess mortality (not statistically significant) from respiratory and digestive cancers was observed among male workers exposed to cutting fluids in metal machining jobs.
Nomenclature for cutting fluid is not standardized. The term generally applies to substances used in drilling, gear cutting, grinding, lathing, milling, and other machining operations, for the purpose of cooling, lubricating, and removing metal or plastic chips, filings, and cuttings from the contact area. These substances are variously referred to as cutting, cooling, grinding, industrial, lubricating, and synthetic oils or fluids.
Commercial cutting fluids can be divided into four categories:
Synthetic cutting fluids, semi-synthetic cutting oils, and soluble cutting oils may contain nitrosamines, as found by Dr. Fine, either as contaminants in amines, or as products from the reaction of amines (e.g., triethanolamine) with nitrite. Straight oils do not contain nitrites or amines but may contain polynuclear aromatic compounds (recognized as having carcinogenic potential).
Since many of the proprietary ingredients of cutting fluids have not undergone complete toxicological evaluation, NIOSH would caution any user contemplating changing from one cutting fluid formulation to another to give full consideration to the potential hazards of the substitute.
Enclosed are some industrial hygiene practices which can help minimize dermal and respiratory exposures to cutting fluids.
The potential for nitrosamine exposure during the use of cutting fluids will be further assessed as part of a proposed NIOSH project to determine the levels of nitrosamines in a number of factory environments. Follow-up epidemiologic studies are also anticipated. Studies of cancer induction in laboratory animals exposed to cutting fluids or cutting fluid components are also planned. In addition, a Criteria for a Recommended Standard which will address the problem of cutting fluids is scheduled to be completed in 1977.
[signature] John F. Finklea, M.D. Director |
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