We investigated whether vital capacity (VC) and forced expiratory volumes in 1 and 3 seconds (FEV1, FEV3) were lower and whether respiratory symptoms were more common in chicken farmers exposed to occupational dusts than in community control subjects and whether smoking had a synergistic influence on the effects of the inhalation of occupational dusts by chicken farmers. Methods: Data were obtained retrospectively from spirometry and questionnaire records of 200 subjects randomly selected from approximately 10,000 persons' records. The 200 subjects were 50 smoking farmers, 50 nonsmoking farmers, 50 smoking controls, and 50 nonsmoking controls. For one part of the study we divided the subjects into two groups of 100 on the basis of occupation only, in order to study the effect of chicken farming independent of the effect of smoking. In another aspect of the study, we made comparisons among the four groups of 50. Results: The 100 farmers as a group had significantly lower FEV than did the 100 controls, but VC and FEV3 were not significantly different. The farmers had a significantly higher incidence of cough, shortness of breath, and chronic bronchitis, but the incidence of wheezing was not significantly different. The 100 smokers as a group had significntly lower VC, FEV1, and FEV3 and a significantly higher incidence of all symptoms. When the four groups of 50 were compared, their pulmonary function values ranked, from best to worst, in the following order: (1) nonsmoking controls, (2) nonsmoking farmers, (3) smoking controls, (4) smoking farmers. Comparison of symptoms among the four groups showed that the incidence of all symptoms was significantly higher in nonsmoking farmers than in nonsmoking controls, significantly higher in smoking controls than in nonsmoking farmers, significantly higher in smoking farmers than in nonsmoking controls, and significantly higher in smoking controls than in nonsmoking controls. The incidence of cough, shortness of breath, and chronic bronchitis (but not wheezing) was significantly higher in smoking farmers than in nonsmoking farmers. There was no significant difference in the incidence of symptoms or in VC, FEV1, or FEV3 between smoking farmers and smoking controls. Conclusions: Our study indicated that when compared to nonsmoking controls, nonsmoking chicken farmers had a higher incidence of respiratory symptoms but not significantly lower pulmonary function; that, in general, smoking farmers and smoking controls had a higher incidence of symptoms and lower pulmonary function values than did nonsmoking farmers and nonsmoking controls; but that in terms of incidence of symptoms and pulmonary function values, smoking farmers were not significantly worse off than smoking controls. However, a synergistic effect of cigarette smoke and the inhalation of farm dusts may take place in the small airways and thus remain undetected by "standard" pulmonary function tests . (Respir Care 1985;30:1042-1048.)
Stewart et al. (Sun,) studied this question.