Updated epidemiology of workers exposed to metalworking fluids provides sufficient evidence for carcinogenicity.

The 1998 National Institute for Occupational Safety and Health (NIOSH) criteria document for metalworking fluids (MWF) is the most recent authoritative review of mortality studies of workers with these exposures. NIOSH concluded that substantial evidence exists for increased risk of cancer at several sites (larynx, rectum, pancreas, skin, scrotum, and bladder) among workers exposed to MWF before the mid-1970s, and that evidence is equivocal for cancer at several other sites, including stomach, esophagus, lung, prostate, brain, colon, and hematopoietic system. The UAW believes that systematic analysis of that body of data makes a much stronger case for stomach cancer related to MWF exposure. Since the Criteria document, the mortality experience of three of the cohorts reviewed has been either updated or reanalyzed. These updates strengthen the evidence for increased mortality from stomach and liver cancer, and non-malignant respiratory disease associated with exposure to water-based metalworking fluids. Additional toxicological data providing clear evidence for carcinogenicity of diethanolamine, a widely used ingredient, also increases the biological plausibility of these findings. Despite changes in composition of MWFs with time, and reduced exposure levels, these data contradict the notion that cancer risks have been eliminated.