OCCUPATIONAL DUST EXPOSURE AND CHRONIC OBSTRUCTIVE PULMONARY-DISEASE - A SYSTEMATIC OVERVIEW OF THE EVIDENCE

The object of this study was to assess the relationship between occupa tional dust exposure and chronic obstructive pulmonary disease (COPD). Studies were identified using MEDLINE (January 1966 to July 1991), SC ISEARCH, manual review of reference lists, and personal contact with m ore than 30 international experts. Studies of COPD, lung function, emp hysema, chronic bronchitis, or mortality in workers exposed to nonorga nic dust were retrieved. Studies were included if dust exposure was me asured quantitatively, and a quantitative relationship between dust ex posure and one of the outcomes of interest was calculated while contro lling at least for smoking and age. Methodological rigor was assessed, and data regarding the study populations, prognostic factors, and out comes were extracted independently by two reviewers. Thirteen reports derived from four cohorts of workers met our inclusion criteria. Three of the cohorts were of coal miners and one was of gold miners. All of the studies found a statistically significant association between los s of lung function and cumulative respirable dust exposure. It was est imated that 80 (95% Cl, 34 to 137) of 1,000 nonsmoking coal miners wit h a cumulative respirable dust exposure of 122.5 gh/m3 (considered equ ivalent to 35 years of work with a mean respirable dust level of 2 mg/ m3) could be expected to develop a clinically important (> 20%) loss o f FEV1 attributable to dust. Among 1,000 smoking miners the comparable estimate was 66 (95% Cl, 49 to 84). The risk of a clinically importan t loss of lung function attributable to dust among nonsmoking gold min ers was estimated to be three times as large as for coal miners at les s than one fifth of the cumulative respirable dust exposure (21.3 gh/m 3), the maximal exposure observed among the cohort of gold miners. We conclude that occupational dust is an important cause of COPD, and the risk appears to be greater for gold miners than for coal miners. One possible explanation of the greater risk among gold miners is the high er silica content in gold mine dust.