COHORT MORTALITY STUDY OF PULP AND PAPER-MILL WORKERS IN BRITISH-COLUMBIA, CANADA

The authors studied a cohort of 30,157 male pulp and paper workers in British Columbia, Canada. Of these, 20,373 worked in kraft mills only, 5,249 in sulfite mills only, and 4,535 in both kraft and sulfite mill s. All workers with at least 1 year of employment on January 1, 1950, or thereafter until December 31, 1992, were studied. Standardized mort ality ratios (SMRs) were used to compare the mortality rates of the co hort with those of the Canadian male population. Ninety percent confid ence intervals (Cls) for the SMRs were obtained. Cancer risks signific antly associated with work duration and time from first employment of 15 years or more were observed: I)total cohort: pleura (SMR = 3.61, 90 % CI 1.42-7.58); kidney (SMR = 1.69, 90% CI 1.13-2.43); brain (SMR = 1 .51, 90% CI 1.05-2.16); 2) workers in kraft mills only: kidney (SMR 1. 92, 90% CI 1.04-3.26); 3) workers in sulfite mills only: Hodgkin's dis ease (SMR = 4.79, 90% CI 1.29-12.37); 4) workers ever employed in both kraft and sulfite mills: esophagus (SMR = 1.91,90% CI 1.00-3.33). The se malignancies have been associated with the following known or suspe cted carcinogens to which pulp and paper workers may have been exposed : asbestos (pleural, biocides (kidney), formaldehyde (kidney, brain, H odgkin's disease), hypochlorite (esophagus). A nested case-control stu dy with detailed exposure assessment is under way to help determine wh ether excess risks for specific cancers reflect exposure among subsets of workers.