MORTALITY STUDIES OF METALWORKING FLUID EXPOSURE IN THE AUTOMOBILE-INDUSTRY - VI - A CASE-CONTROL STUDY OF ESOPHAGEAL CANCER

Background Results are reported from a nested case-control study of 60 esophageal cancer deaths among 46,384 automobile manufacturing worker s potentially exposed to metalworking fluids (MWF) in machining and gr inding operations. Methods By using incidence-density sampling, contro ls were selected with a sampling ratio of 20:1 from among co-workers w ho remained at risk by the age of death of the case, matched on race, gender plant, and year of birth. Conditional logistic regression was u sed to evaluate the risk associated with cumulative exposure (mg/m(3)- years) to each of thr ee types of metalworking fluid (straight, solubl e, and synthetic MWF), as well as with years of exposure to selected c omponents of MWF, including nitrosamines, sulfur, biocides, and severa l metals. Results Esophageal cancer was found to be significantly asso ciated with exposure to both soluble and synthetic MWF in grinding ope rations. The odds ratios (ORs) for grinding with soluble MWF were elev ated at 2.5 or greater in all categories of cumulative exposure, altho ugh the exposure-response trend was statistically significant only whe n exposure was measured as duration. Those with 12 or more years expos ure to soluble MWF in grinding operations experienced a 9.3-fold relat ive 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 nitrosamin es, 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 gri nding with synthetics, nitrosamines and biocides, it was nor possible to separate the specific risks associated with these components. (C) 1 998 Wiley-Liss, Inc.