RESPIRATORY HEALTH OF WORKERS EXPOSED TO METAL DUSTS AND FOUNDRY FUMES IN A COPPER REFINERY

Objectives-To assess airflow limitation in workers exposed long term t o metal dust, the prevalence of pleural plaques in those workers expos ed in the past to asbestos, the influence of pleural plaques on lung f unction, and the possible association with airway disease caused by as bestos. Methods-A cross sectional and longitudinal (seven year) survey of 494 long term (mean (SEM) 21(1) years) workers in a copper refiner y was carried out from medical questionnaires, chest radiographs, and forced spirometry. Results-The prevalence of lifetime nonsmokers was 1 9%, current smokers 39%, and ex-smokers 42%. The prevalence of chronic obstructive pulmonary diseases (COPD) (forced expiratory volume in on e second (FEV(1)) < 80% predicted) was 5%, small airway dysfunction (S AD) (maximal mid-expiratory flow (MMEF) < 60% predicted) was 7%, and t his did not differ from the control population. The COPD and SAD were associated with cumulative smoking index but not with the cumulative w ork years at the plant or with any type of work at the plant. The mean (SEM) reduction of FEV, was 20(7) ml in non-smokers, 26(4) ml in smok ers, and 26(5) ml in ex-smokers (P > 0.05). In the smokers and ex-smok ers with COPD, the loss of FEV(1) was 53(10) (P < 0.02). The prevalenc e of pleural plaques was 11% (P < 0.0001); pleural plaques were found in older workers with known exposure to asbestos. The pleural plaques were circumscribed and associated with a non-significant 196 ml reduct ion in forced vital capacity (FVC) and non-significant reduction of FV C over time. The pleural plaques were not associated with COPD or SAD. The cumulative smoking index obtained by a technician did not differ from that by a chest physician. Conclusions-Despite exposures to asbes tos that produced pleural plaques and exposures to metal dusts and fou ndry fumes the long term workers of this plant did not have excessive prevalence of COPD or SAD. The data suggest that low level long term e xposure to metal dusts, gases, and foundry fumes do not necessarily ca use respiratory dysfunction, circumscribed pleural plaques with low gr ades of width and extent do not reduce FVC significantly, and exposure to asbestos dust that produced pleural plaques does not necessarily p roduce airway dysfunction.