MORTALITY STUDIES OF MACHINING FLUID EXPOSURE IN THE AUTOMOBILE-INDUSTRY .3. A CASE-CONTROL STUDY OF LARYNX CANCER

A case-control study of larynx cancer was conducted within a cohort of automobile workers exposed to metal working fluids, commonly referred to as machining fluids (MF). Results are based on 108 cases of larynx cancer and 5:1 matched controls. Risks associated with specific types of MF, as well as specific components of the fluids were evaluated. B ased on a retrospective exposure assessment, lifetime exposures to str aight and soluble fluids, grinding particulate, biocides, selected met als, sulfur, and chlorine were examined. Exposure to asbestos and acid mists at two of the three study sites was also characterized. Results suggest that straight mineral oils are associated with almost a two-f old excess in larynx cancer risk. There was also evidence of an associ ation with elemental sulfur, commonly added to straight MF to improve the integrity of the materials under extreme pressure and heat. It is not clear whether sulfur is causally related to an excess relative ris k of larynx cancer or whether the observed association is the result o f unmeasured confounding by another contaminant or process feature. Fo r example, the high stress operations that require MF enriched with su lfur are also more likely to produce polycyclic aromatic hydrocarbons (PAHs) during the process. Thus, the observed association with sulfur may be due to an association with PAH. The finding of excess risk of l aryngeal cancer associated with MF is consistent with several previous reports in the literature. This is the first study, however, to disti nguish straight mineral oils from other types of MF. Based on these fi ndings, a general reduction in concentrations of straight mineral oil particulate in occupational environments would be prudent. (C) 1994 Wi ley-Liss, Inc.