Prostate cancer incidence in relation to time windows of exposure to metalworking fluids in the auto industry.
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.
Agalliu
Ilir
I
Department of Work Environment, University of Massachusetts, Lowell, MA, USA.
Kriebel
David
D
Quinn
Margaret M
MM
Wegman
David H
DH
Eisen
Ellen A
EA
D000328:Adult; D001336:Automobiles; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D015986:Confounding Factors, Epidemiologic; D006801:Humans; D015994:Incidence; D007219:Industrial Oils / Q000633:toxicity*; D007221:Industry; D016015:Logistic Models; D008297:Male; D008669:Metallurgy; D008824:Michigan / Q000453:epidemiology; D009784:Occupational Diseases / Q000453:epidemiology*; D016273:Occupational Exposure / Q000009:adverse effects*; D016016:Proportional Hazards Models; D011471:Prostatic Neoplasms / Q000453:epidemiology*; D012042:Registries; D012307:Risk Factors; D013997:Time Factors