Increased bronchial reactivity to inhaled histamine in nonsmoking grain workers with normal lung function

We measured nonspecific bronchial reactivity to inhaled histamine in 26 lifetime nonsmoking grain handlers and 29 lifetime nonsmoking unexposed control subjects matched for age, sex and specific conductance. Routine lung function tests revealed a total lung capacity that was higher in control subjects than in workers (P less than 0.05) with no difference in other subdivisions of lung volume, or expiratory flow rates between the two groups. An index of allergy was significantly greater in the control subjects than in the grain workers (P less than 0.01). None of the grain handlers was sensitive to grain dust by history or by skin tests. Respiratory symptoms (cough, sputum, dyspnea, or wheezing) were more prevalent in the grain workers than in controls (P less than 0.05). The mean concentration of histamine required to reduce the specific conductance by 35 percent was 4.5 +/- 2.0 mg/ml in grain workers and 5.9 +/- 3.0 mg/ml in controls (P less than 0.05). Chronic exposure to grain dust in nonallergic individuals appears to be associated with both increased prevalence of respiratory symptoms and increased nonspecific bronchial reactivity when compared to nonexposed control subjects.