and hand cleaning in some areas during 1955-1968. The investigators determined that 32% had “frequent” exposures to peak concentrations (one or two daily peaks of about 15 minutes to trichloroethylene at 200-600 parts per million [ppm]) during vapor degreasing. Work areas were located in very large buildings with few internal partitions, which aided dispersion of trichloroethylene. (This is different from the Henschler et al.  and Vamvakas et al.  studies, which generally had small enclosed work areas.) However, only a small number of subjects with “high” exposure had long-duration exposures, no more than 16%. Additionally, few workers were exposed only to trichloroethylene; most had mixed exposures to other chlorinated and nonchlorinated solvents. Nonetheless, these modest exposures were associated with some findings suggestive of increases in liver and biliary cancer, multiple myeloma, and non-Hodgkin’s lymphoma that were consistent with studies in animals.
A strong exposure assessment was performed, but precision in the exposure assignments was limited by the company’s vague personnel data. The cohort had a modest number of highly exposed (about100 ppm) subjects, but overall most were exposed to low concentrations (about 10 ppm) of trichloroethylene.
This study reported on the overall mortality of a cohort of workers in the aircraft manufacturing industry in southern California. The only exposure metric was years of work. An estimated 37% of the cohort was estimated to be potentially exposed to trichloroethylene, but no information was presented on how they were exposed. Given the enormous misclassification on exposure, the effect of exposure would have to be very large to be detected as an overall risk for the population. Negative findings are to be expected.
The exposure assignments were insufficient to define exposures of the cohort and the frequency of exposures was likely low. Therefore, this study was not useful for determining whether trichloroethylene is related to increased disease risk.
This study evaluated a cohort of 20,508 aircraft manufacturing workers in Arizona. The company conducted a limited semiquantitative assessment