DECREASED VENTILATORY FUNCTION IN HARD METAL WORKERS

Objectives-To study individual effects on pulmonary function of exposu re to hard metal including cobalt. Methods-All of the workers in a har d metal company (583 men and 120 women) were examined for smoking, res piratory symptoms, ventilatory function, occupational history of expos ure to hard metal, and present exposure to airborne cobalt. The ventil atory function indices (forced vital capacity (FVC), forced expiratory volume in one second (FEV(1)), forced expiratory volume in one second per cent (FEV(1)%), peak expiratory flow (PEF), mid-maximal flow (MMF ), forced expiratory flow at 50% vital capacity (V-50), forced expirat ory flow at 25% vital capacity (V-25)) were standardised for height an d age and expressed as a percentage of predicted values. Results-Two w ay analysis of variance of indices of ventilatory function showed that an interaction of hard metal exposure and smoking decreased %V-50 for both men and women. Among the currently exposed men, those with asthm atic symptoms (defined as reversible dispnoea with wheeze) had signifi cantly lower %FVC, %FEV(1)%, %PEF, %MMF, %V-50, and %V-25 than did wor kers without asthma. The ventilatory disfunction did not differ betwee n exposed and nonexposed workers with asthmatic symptoms. Even among t he men without asthmatic symptoms, %V-50 was significantly lowered by the interaction of hard metal exposure and smoking. The multilinear re gression analysis of indices of ventilatory function for all of the su bjects on sex, smoking (Brinkman index), exposure to hard metal, and a sthmatic symptoms showed that asthmatic symptoms and smoking had signi ficant effects on all variables and that the decrease in %V-25 was ass ociated with hard metal exposure. In the currently exposed and non-exp osed workers, multilinear regression analysis applying indices for cob alt exposure (mean cobalt concentration, duration of exposure, and cum ulative dose) showed that not only asthmatic symptoms or smoking but a lso duration of exposure had significant decreasing effects on %FVC, % MMF, and %V-25. Conclusions-Occupational exposure to hard metal probab ly causes impairment of ventilatory function in a dose dependent manne r.