Cohort mortality study of Swedish pulp and paper mill workers—nonmalignant diseases

Abstract

The aim of this study was to determine mortality among pulp and paper mill workers according to the main mill pulping process, department, and gender, particular reference being given to diseases of the circulatory and respiratory systems. The cohort of 18 163 men and 2 291 women employed between 1939 and 1999 and with >1 year of employment was followed for mortality from 1952 to 2001 (acute myocardial infarction from 1969). Standardized mortality ratios (SMR) with 95% confidence intervals (95% CI) were estimated by comparing the observed number of deaths with the expected number for the entire Swedish population. Exposure was assessed from personnel files in the mills. Data from an exposure measurement database are also presented. There were 5898 deaths in the cohort. Total mortality had an SMR of 1.02 (95% CI 0.98-1.06) for the men in the sulfate mills and an SMR of 0.93 (95% CI 0.90-0.97) for the men in the sulfite mills. Mortality from acute myocardial infarction was increased among the men in both the sulfate and sulfite mills [SMR 1.22 (95% CI 1.12-1.32) and SMR 1.11 (95% CI 1.02-1.21), respectively] and by department in sulfate pulping (SMR 1.29, 95% CI 1.07-1.54), paper production (SMR 1.26, 95% CI 1.06-1.49), and maintenance (SMR 1.16, 95% CI 1.02-1.30). Mortality from cerebrovascular disease, diabetes mellitus, and nonmalignant respiratory diseases was not increased. Death from acute myocardial infarction, but not cerebrovascular diseases, was increased in this cohort and was probably related to a combination of different occupational exposures (eg, dust, sulfur compounds, shift work, and noise).