EPIDEMIOLOGIC-STUDY OF HARD METAL ASTHMA

Objectives-To elucidate factors contributing to hard metal asthma, the entire workforce of a corporation producing hard metal tools (n = 703 ) was examined. Methods-The variables evaluated were the atopy reflect ed by immunoglobulin E (IgE) antibody against mite allergen, history o f exposure to hard metal, smoking, concentration of airborne cobalt, s pecific IgE antibody reaction against cobalt, and the respiratory symp tom of attacks of reversible dyspnoea with wheeze (asthmatic symptoms) . Results-Univariate analysis showed that the prevalence of the asthma tic symptoms was significantly higher in formerly and currently expose d male workers than in non-exposed male workers. Positive IgE reaction against cobalt was found in seven men (2.0%), all of whom had asthmat ic symptoms. Furthermore, it was found that atopy, positive IgE antibo dy against cobalt, and age of 40 or older were significantly correlate d with asthmatic symptoms. Multilogistic analysis on the same factors and smoking in all of the workers showed that the age, experience of h ard metal exposure, and atopy were significant risk factors associated with the asthmatic symptoms. Multilogistic analysis of data for curre ntly exposed and nonexposed workers also showed that age and atopy wer e risk factors, and that the exposure to cobalt at the low concentrati on (at or below 50 mu g/m(3)) but not at the higher concentration was a significant risk factor. Exposure to mist of coolants containing ion ic cobalt, used during grinding, was not found to be any more hazardou s in terms of onset of asthmatic symptoms than exposure to hard metal dust containing metallic cobalt. Conclusions-Accordingly, it is conclu ded that both environmental factors and individual susceptibility shou ld be taken into consideration in efforts to reduce the prevalence of hard metal asthma.