Mortality and cancer experience of Quebec aluminum reduction plant workers. Part I: The reduction plants and coal tar pitch volatile (CTPV) exposure assessment

Objectives: This paper presents the exposure assessment and job-exposure matrix (JEM) used to estimate coal tar pitch volatile (CTPV) exposure for a study of mortality and cancer incidence in aluminum smelter workers in Quebec, Canada. Methods: Historical CTPV exposure was assessed by estimating benzene-soluble material (BSM) and benzo[ a]pyrene (B[ a]P) levels for combinations of job and time period. Estimates were derived by using several procedures including averaging measurement data, a deterministic mathematical model using process-related correction factors, and expert-based extrapolation. Results: The JEM comprised 28,910 jobs, covering 7 facilities from 1916 to 1999. Estimated exposures ranged from 0.01 mu g/m(3) to 68.08 mu g/m(3) (B[a] P) and 0.01 mg/m(3) to 3.64 mg/m(3) (BSW) and were lowest before 1940 and after 1980. Conclusion: This methodology constitutes an improvement compared with methods used for previous studies of the Quebec cohort.