EFFECTS OF IMPROVEMENTS IN WORKING CONDITIONS ON OCCUPATIONAL ASTHMA

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  • 作業環境の改善が職業性喘息に及ぼす影響について

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Hoya (sea-squirt)-asthma is an occupational disease observed among oyster-raisers. Over a period of 21 years(1963-1984), many devices were introduced in an attempt to protect the workers at the oyster-shucking plant in Hatsukaichi, Hiroshima Pref. These devices included a joint workshop, an oyster-washer, an irrigation-pool for oyster-shells, an improvement in the mallets used for shucking whereby scattering is reduced, a half facepiece for workers to prevent facial exposure and hyposensitization for workers already suffering from Hoya-asthma. A study was conduced to evaluate the effects of these devices on the prevalence rate of Hoya-asthma. 1) The prevalenc rates of Hoya-asthma in 1963, 1968, 1976 and 1984 were 36.0%, 18.7% 15.8% and 7.4%, respectively, showing a marked decrease over the years. 2) The percentage of severe cases among the Hoya-asthma patients were 28.8%(1963), 2.7%(1968), 2.7%(1976), 0%(1984), also showing a marked decrease. This was accompanied by an increase of mild cases(34.8%, 78.4%, 75.7%, 88.2%, respectively for the same years as above). 3) The specific IgE level in sera of the Hoya-asthma patients went down during the off-season when there's less chance of exposure to antigens, compared with the level during the oyster season. The specific IgE level in the sera of 4 cases without asthma-attack even after the cessation of hyposensitization, showed a year-by-year lowering tendency. 4) On the other hand, on an island where workers receive insufficient workplace protection, the prevalence rate of Hoya-asthma in 1984 was as high as 37.9%. We conclude that an improvement in environmental working conditions produces favorable effects on occupational asthma, such as a decrease in the prevalence rate, a reduction of severity and a lowering of specific IgE levels in sera.

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