Exposure to mushroom spores may cause many respiratory allergic diseases, however, there has been no serial study in a mushroom factory to address this problem. The aim of this study was to investigate the serial changes in respiratory allergy and the incidence of hypersensitivity pneumonitis (HP) in mushroom workers. A 3-year follow-up study, beginning in June 1996, was conducted in a newly operating mushroom factory in which one kind of mushroom is produced: Hypsizigus marmoreus (Bunashimeji). Allergic symptoms, chest roentgenogram, serum precipitins to the spores and soluble adhesion molecules in sera were evaluated once a year in 60 workers and 20 controls. Three out of the 60 subjects were diagnosed as having HP caused by inhalation of the mushroom spore and they were therefore excluded from this study, and the 57 non-HP subjects were evaluated. In this study 24 workers quit because of intolerable cough, runny nose, wheezing, sputum, fever elevation and/or shortness of breath at their place of work. During each year of this study as many as 70-80% of employees suffered some of the above symptoms, cough being the most frequent, and positive rate of serum precipitins to the spore revealed 30% in 1996, 93% in 1997 and 94% in 1998. From the June 1996 examination until the following May, serum soluble intercellular adhesion molecule-1 levels of the 15 workers who quit during that period were significantly higher than those in the 42 workers still employed in 1997 (P < 0 .05). Workers in Bunashimeji mushroom factories might be at critical risk of developing respiratory allergy. In our 3-year study, over 90% workers were sensitized to the spore, 40% quit because of the symptoms and 5% developed HP. It was suggested that workers should be counselled about the risk of mushroom allergy and precautionary measures should be taken to prevent its occurrence.
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