[The effect of grain dust on non-specific bronchial hyperreactivity]

246 grain elevator or mill workers were divided into heavy-exposure group and light-exposure group and methacholine provocation tests, were carried out. After provocation test, FEV1, FVC, MMEF, PEF, V50 and V25 significantly decreased in heavy exposure than those in light exposures. (P less than 0.01). 18.9% of heavy-exposure was associated with bronchial hyperreactivity, which was significantly higher than that of light-exposure (4.4%). The incidence of more than 10% declines in FVC or FEV1 and 25% in PEF or V25 during one day or one week work-shift was significantly higher in workers with bronchial hyperreactivity than in those without bronchial hyperreactivity (P less than 0.01). The findings indicated that exposure to heavy concentration of grain dust for long period can impair pulmonary function and cause nonspecific bronchial hyperreactivity.