Background: Occupational exposure to mineral oil-based metalworking fluids has been consistently linked with skin conditions such as contact dermatitis and squamous cell skin cancer, especially of the scrotum. We examined the incidence of malignant melanoma in a study of autoworkers.
Methods: We followed a cohort of autoworkers from 1985 through 2004 for cancer incidence. Hazard ratios (HRs) were estimated in Cox models for cumulative exposure to total particulate of straight fluid (neat oil), soluble fluid (oil emulsified in water), and synthetic fluid (no oil). Exposure was partitioned into time windows by latency and by calendar periods defined by changes in the content of polycyclic aromatic hydrocarbon in the refined oils. The population was restricted to workers born after 1935. We examined the date-of-birth restriction in a sensitivity analysis.
Results: On the basis of 76 incident cases of malignant melanoma in the cohort of 14,139 white males, the HR was 1.99 (95% confidence interval = 1.00-3.96) for the highest category of straight fluid. Risk was greatest in the most recent time window. Penalized splines suggested a linear exposure-response over the full range of exposure. The change in HR for malignant melanoma per mg/m3-year of straight fluid increased monotonically from 1.01 to 1.04, when the date-of-birth restriction increased from 1925 to 1945 in 5-year intervals. Results for soluble fluid were more modest. There was no association with synthetic fluid.
Conclusions: Results provide evidence, based on quantitative measures of metalworking fluid, that oil-based fluid, particularly straight mineral oils, are associated with the incidence of malignant melanoma.