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.
Copyright © 2011 Wiley-Liss, Inc.