Distinguishing the Common Components of Oil- and Water-Based Metalworking Fluids for Assessment of Cancer Incidence Risk in Autoworkers

Background Metalworking fluids (MWF)-straight, soluble, and synthetic-have overlapping components. We derived constituent-based metrics of polycyclic aromatic hydrocarbons (PAHs), water-based MWF, biocides, and nitrosamines to account for this overlap and examined their relations with cancer incidence. Methods An autoworkers cohort of 30,000 was followed for cancer incidence. Hazard ratios were estimated for each cancer and cumulative exposure (lagged) to each new metric; soluble MWF contributed variably to several metrics with weight k = 0-1. Results For most cancer sites, the constituent-based metrics resulted in stronger exposure-disease associations than the MWF classes alone. Laryngeal and bladder cancer were most strongly associated with PAH (k = 0). Protective effects for stomach and lung cancer were observed with biocide, a component that may be a surrogate for endotoxin. Conclusions Our findings provide support and clarification of possible etiologies for previous positive associations and provide support for distinguishing exposure from oil-and water-based MWF in epidemiologic studies. Am. J. Ind. Med. 54: 450-460, 2011. (C) 2011 Wiley-Liss, Inc.