Persistence of N-nitrosodiethanolamine contamination in American metal-working lubricants

The potent carcinogen N-nitrosodiethanolamine (NDELA) was discovered as a contaminant of commercial metal-working lubricants over a decade ago. To determine whether or not improvements in industrial practice suggested in the meantime have eliminated this contamination from United States products, a selection of cutting fluids obtained from the current marketplace was analysed for NDELA content. All six semi-synthetic fluids examined contained NDELA at levels ranging from 0.5 to 4.3 ppm. Three of six petroleum-based lubricants and five of six synthetics also contained significant NDELA (when analysed at a detection limit of 0.03 ppm), at levels of up to 0.16 and 55 ppm, respectively. The mean concentrations were 1.5 ppm for the semi-synthetics, 0.07 ppm for the petroleum-based products, and 11.4 ppm for the synthetic metal-working fluids. While these levels are far below the values of 1-2% by weight (10,000-20,000 ppm) found in some contaminated products 13 years ago, they may nevertheless pose a continuing health risk for the machinists who work with them.