Abstract

OBJECTIVES: To study individual effects on pulmonary function of exposure to hard metal including cobalt. METHODS: All of the workers in a hard metal company (583 men and 120 women) were examined for smoking, respiratory symptoms, ventilatory function, occupational history of exposure to hard metal, and present exposure to airborne cobalt. The ventilatory function indices (forced vital capacity (FVC), forced expiratory volume in one second (FEV1), forced expiratory volume in one second per cent (FEV1%), peak expiratory flow (PEF), mid-maximal flow (MMF), forced expiratory flow at 50% vital capacity (V50), forced expiratory flow at 25% vital capacity (V25)) were standardised for height and age and expressed as a percentage of predicted values. RESULTS: Two way analysis of variance of indices of ventilatory function showed that an interaction of hard metal exposure and smoking decreased %V50 for both men and women. Among the currently exposed men, those with asthmatic symptoms (defined as reversible dispnoea with wheeze) had significantly lower %FVC, %FEV1%, %PEF, %MMF, %V50, and %V25 than did workers without asthma. The ventilatory disfunction did not differ between exposed and non-exposed workers with asthmatic symptoms. Even among the men without asthmatic symptoms, %V50 was significantly lowered by the interaction of hard metal exposure and smoking. The multilinear regression analysis of indices of ventilatory function for all of the subjects on sex, smoking (Brinkman index), exposure to hard metal, and asthmatic symptoms showed that asthmatic symptoms and smoking had significant effects on all variables and that the decrease in %V25 was associated with hard metal exposure. In the currently exposed and non-exposed workers, multilinear regression analysis applying indices for cobalt exposure (mean cobalt concentration, duration of exposure, and cumulative dose) showed that not only asthmatic symptoms or smoking but also duration of exposure had significant decreasing effects on %FVC, %MMF, and %V25. CONCLUSIONS: Occupational exposure to hard metal probably causes impairment of ventilatory function in a dose dependent manner.