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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.

Twenty-eight men with the Pi MZ phenotype who have been employed in the Saskatchewan country grain elevators and thus regularly exposed to high levels of grain dust, were case matched for age, years of employment, employment status, smoking status, and smoking history with grainworkers of type Pi M. Individuals answered a questionnaire, had a chest roentgenogram, skin tests, and performed a battery of pulmonary function tests. There were no differences between the two groups in prevalence of symptoms or atopy. Although not statistically significant, the MZ group had three times as many individuals with abnormal roentgenograms suggestive of COPD as the M group. The Pi MZ grainworkers had consistently poorer mean results for the pulmonary function tests with significantly lower mean values for FEV1, FEV1/FVC, MMFR, and Vmax50, leading us to suggest that Pi MZ individuals may be at higher risk of COPD than Pi M individuals, but only in the presence of other risk factors such as grain dust exposure.

To determine whether clinical symptoms and pulmonary function abnormalities were more common in lifetime nonsmoking grain elevator workers exposed to grain dust than in lifetime nonsmoking community control subjects who were not occupationally exposed to dust, we obtained an occupational health questionnaire, spirometric variables, and flow-volume curves on 90 lifetime nonsmoking grain workers and 90 lifetime nonsmoking community control subjects. For these groups we calculated the prevalence of chronic bronchitis, defined as daily production of phlegm for 3 months/yr for at least 2 yr. The prevalence of chronic bronchitis was higher in nonsmoking workers (23.1%) than in nonsmoking control subjects (3.3%) (p less than 0.01). Nonsmoking grain workers had lower mean values than did nonsmoking control subjects for maximal mid-expiratory flow rate (p less than 0.01) and for maximal expiratory flow at 50% of vital capacity (p less than 0.01). We conclude that exposure to grain dust inlifetime nonsmoking grain workers is associated with an increased prevalence of chronic bronchitis and evidence of airflow obstruction.

We studied two groups of young male cereal grain elevator workers: 82 lifetime nonsmoking grain workers (2.5 +/- 1.2 yr of dust exposure) who were 22.7 +/- 3.5 yr of age, and 82 smoking grain workers (6.1 +/- 4.1 pack-years of smoking) individually matched to the nonsmoking grain workers for age (22.7 +/- 3.3 yr) and years of work in the grain industry (2.6 +/- 1.3 yr). We also studied the following groups of community control subjects: 82 nonsmoking community control subjects individually matched to the nonsmoking grain workers for age (22.8 +/- 3.7 yr), and 82 smoking community control subjects individually matched to the smoking grain workers for age (22.7 +/0 3.6 yr) and smoking history (6.0 +/- 4.0 pack-years). We measured forced expiratory volume in one second (FEV1), forced vital capacity (FVC), FEV1/FVC %, the maximal mid-expiratory flow rate (FEF25-75), the flow at 50% (Vmax50) and 25% (Vmax25) of a maximal expiratory flow-volume maneuver, the percent increase in the maximal expiratory flow at 50% FVC breathing a mixture of 80% helium-20% oxygen as compared with air (delta Vmax50), and the slope of Phase III of the single breath nitrogen test (delta N2/L). We also assessed the prevalence of respiratory symptoms from responses to a standardized questionnaire. Smoking was associated with an increased prevalence of cough, wheezing, and dyspnea, and a mildly decreased FEV1/FVC %. Two variables were used as indexes of small airway dysfunction, a lower delta Vmax50 and a higher delta N2/L. Only the group of workers who both smoked and were occupationally exposed to grain dust had evidence of small airway dysfunction. The differences in delta N2/L and delta Vmax50 were greater than was expected from an additive model, suggesting that the combined effects of occupational exposure to grain dust and inhalation of cigarette smoke may have a synergistic effect leading to small airway dysfunction in young cereal grain workers.

In four groups of individually-matched subjects (nonsmoking grain workers, smoking grain workers, nonsmoking community controls, and smoking community controls) we measured pulmonary function variables from the spirogram, from the maximal expiratory flow-volume curve breathing air and helium, and from the single breath nitrogen test as well as symptom prevalences from a questionnaire in order to assess the relative effects of smoking and occupational exposure to grain dust in Saskatchewan country grain elevators. There were similar increased prevalences of respiratory symptoms and reductions in pulmonary function associated with either grain dust exposure or smoking, but the effects of smoking were slightly more pronounced. The combined effects of grain dust and smoking on lung function appeared to be additive except in the least exposed workers (five years or less) where a synergistic effect was observed in tests of peripheral airways dysfunction.