Case-control study on renal cell cancer and occupational exposure to trichloroethylene. Part I: Exposure assessment.

A method for a semi-quantitative retrospective assessment of exposure to trichloroethylene (TCE) was implemented for a case-control study conducted in the Arve valley (France), an area with a widely developed screw-cutting industry, where teams of occupational physicians have collected a large quantity of well-documented measurements. A task-exposure matrix was developed to link the main working circumstances in a screw-cutting workshop to corresponding TCE-exposure levels: a 'basic level' was assigned to each task, standing for usual working procedures; exposure circumstances, such as duration or distance from the TCE source, were introduced as corrective factors. In parallel, a detailed occupational questionnaire was designed, setting subjects' descriptions of their successive jobs and working circumstances against levels assessed in the matrix. Possible exposure to TCE, plus some other occupational compounds (other solvents, oils, some metals, asbestos, welding fumes and ionizing radiations), were assessed for any job in all job histories. An average level of exposure to TCE, related to an 8 h usual working day, was attributed to each job period in turn, which was then categorized into six classes: 0; 1-35; 35-50; 50-75; 75-100; and >100 p.p.m. A total of 402 study subjects described their occupational life (average 3.7 jobs/subject, from 1924 to 2003). About 19% of the 1486 job periods described were assessed as being exposed to TCE; of these, 72.2% involved levels<35 p.p.m., 13.2% involved levels>50 p.p.m. and 5.4% above the French occupational exposure limit of 75 p.p.m. (TWA 8 h). A total of 41 job periods included exposure with peaks. Compared with levels encountered in other studies, the more severely exposed part of our study population seemed more exposed than most other populations previously studied, owing to vapor degreasing practices.