Search

Background: Exposure to metalworking fluids has been previously associated with prostate cancer mortality in a cohort of autoworkers. Our objective was to further explore this finding in a study of prostate cancer incidence in the same cohort, with reduced misclassification of outcome., Methods: We conducted a nested case-control study in the General Motors cohort of autoworkers. Incident cases of prostate cancer (n = 872) were identified via the Michigan Cancer Registry from 1985 through 2000. Controls were selected using incidence-density sampling with 5:1 ratio. Using cumulative exposure (mg/m-years) as the dose metric, we first examined varying lengths of lags (0-25 years). Then, we evaluated consecutive windows of exposure: 25 or more years before risk age, and fewer than 25 years. We used penalized splines to model the relative risk as a smooth function of exposure, and adjusted for race and calendar year of diagnosis in a Cox model., Results: Risk of prostate cancer increased with exposure to soluble and straight fluids 25 years or more before risk age but not with exposure in the last 25 years. The relationship with soluble fluids was piecewise linear, with a small increase in risk at lower exposures followed by a steeper rise. By contrast, the relationship with straight fluids was linear, with a relative risk of 1.12 per 10mg/m-years of exposure (95% confidence interval = 1.04-1.20)., Conclusions: Exposure to oil-based fluids, soluble and straight, is modestly associated with prostate cancer risk among autoworkers, with a latency period of at least 25 years.

Objective: Results are presented for a registry-based study of hepatobiliary cancer (liver and biliary tract) nested in a cohort of workers from three automobile manufacturing plants with potential exposure to metalworking fluids., Methods: Altogether 63 cases of hepatobiliary cancer were identified from the cohort by the Michigan cancer registries. Each case was matched to 10 controls. Odds ratios (OR) were estimated in conditional logistic regression models for lifetime exposure to straight, soluble, and synthetic metalworking fluid and fluid components., Results: Overall, hepatobiliary cancer was not associated with exposure to metalworking fluids. However, when the cases were stratified into liver cancer (N = 39) and biliary tract cancer (N = 24) the risk was nonhomogeneous across the two categories. While liver cancer was not associated with exposure to metalworking fluids, the results suggested a possible excess risk of biliary tract cancer with more than 1.0 mg/m3-years of exposure to straight metalworking fluids [OR 2.7, 95% confidence interval (95% CI) 0.9-7.6], as well as any exposure to chlorinated paraffins (OR 3.9, 95% CI 0.9-17). When exposures to straight metalworking fluids were separated into 10-year exposure periods, the odds ratio increased to 6.24 (95% CI 1.62-24.16) for exposures occurring > 20 years prior to the risk date., Conclusions: There is limited evidence that exposure to straight metalworking fluids is associated with biliary tract cancer. The small numbers of cases of these rare cancers were reflected in the wide confidence intervals, and these findings need to be examined further in other exposed populations.

Background: Results are reported from a nested case-control study of 60 esophageal cancer deaths among 46,384 automobile manufacturing workers potentially exposed to metalworking fluids (MWF) in machining and grinding operations., Methods: By using incidence-density sampling, controls were selected with a sampling ratio of 20:1 from among co-workers who remained at risk by the age of death of the case, matched on race, gender, plant, and year of birth. Conditional logistic regression was used to evaluate the risk associated with cumulative exposure (mg/m3-years) to each of three types of metalworking fluid (straight, soluble, and synthetic MWF), as well as with years of exposure to selected components of MWF, including nitrosamines, sulfur, biocides, and several metals., Results: Esophageal cancer was found to be significantly associated with exposure to both soluble and synthetic MWF in grinding operations. The odds ratios (ORs) for grinding with soluble MWF were elevated at 2.5 or greater in all categories of cumulative exposure, although the exposure-response trend was statistically significant only when exposure was measured as duration. Those with 12 or more years exposure to soluble MWF in grinding operations experienced a 9.3-fold relative risk of esophageal cancer mortality (95% CI = 2.1-42.1). The OR for ever grinding with synthetic MWF was 4.1 (95% CI = 1.1-15.0). Elevated risk was also associated with two agents found in both synthetic and soluble fluids, nitrosamines, and biocides. For exposure to nitrosamines, the OR was 5.4 (95% CI = 1.5-19.9); for biocides the OR was 3.8 (95% CI = 0.8-18.9). However, because the same workers were exposed to grinding with synthetics, nitrosamines and biocides, it was not possible to separate the specific risks associated with these components.

A total of 1,811 automobile workers at three General Motors facilities were evaluated by questionnaire for possible respiratory effects resulting from airborne exposures to metal-working fluids (MWF): 1,042 currently worked as machinists and were exposed to one of three types of MWF aerosols (straight mineral oils, soluble oil emulsions, or water-based synthetic fluids that contained no oils); 769 assembly workers, without direct exposure, served as an internal reference group (of these, 239 had never worked as machinists). Symptoms of usual cough, usual phlegm, wheezing, chest tightness, and breathlessness, as well as physician-diagnosed asthma, and chronic bronchitis were the primary outcomes examined. Machinists as a whole had higher prevalence of cough, phlegm, wheezing, and breathlessness than that of assembly workers. Adjusting for confounding, phlegm and wheeze were associated with increasing levels of current exposure to straight oils; cough, phlegm, wheeze, chest tightness, and chronic bronchitis were associated with increasing levels of current exposure to synthetics. In models that included both past and current exposure, only current exposures to straight and synthetic fluids were associated with current symptoms.