Respiratory symptoms and pulmonary function in farmers

A questionnaire was given to 1,824 farmers and 556 control subjects in Saskatchewan to assess respiratory health and pulmonary function tests. With data corrected for age and smoking, farmers were found to have increased prevalences of the respiratory symptoms of phlegm, wheeze, shortness of breath, and the condition of chronic bronchitis. In addition, farmers had significantly lower values for the pulmonary function test variables forced vital capacity (FVC), forced expired volume in one second (FEV1) and maximum midexpiratory flow rate. However, the FEV1/FVC ratio was slightly but significantly greater in farmers than in control subjects. These findings suggest an increase in respiratory symptoms in farmers compared with rural control subjects who are not farmers and a decrease in lung volume and expired flow rates. The slightly high FEV1/FVC ratio may indicate a mixed obstructive and restrictive picture.

Pulmonary function and respiratory symptoms in potash workers

Over 94% of the workers in each of four Saskatchewan potash mines participated in a respiratory health surveillance program that included a questionnaire and pulmonary function tests. Compared with a nonexposed control group, potash workers had higher prevalences of cough, dyspnea, and chronic bronchitis but better pulmonary function. Prevalences of symptoms and pulmonary function abnormalities were similar among workers at the four mines tested and at the various job locations. Potash dust, diesel fumes, and other air contaminants may have an irritant effect that leads to the increased prevalences of cough and chronic bronchitis. Although we found no adverse effects of the potash mine environment on pulmonary function, these findings reflect a healthy worker effect or some selection process that makes the potash workers appear healthier in a cross-sectional study.

Effects of grain dust exposure and smoking on respiratory symptoms and lung function

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.

Effects of smoking and occupational exposure on peripheral airway function in young cereal grain workers

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.

Sensitivity and specificity of early diagnostic tests of lung function in smokers

What are the relative sensitivities and specificities of the "early" tests of lung dysfunction? We describe the findings from a study of virtually the entire population of a rural pollution-free community. Using abnormal spirometry as a marker of obstructive disease, we evaluated the two tests obtained from the single-breath nitrogen curve, closing volume (CV/VC) and the slope of the alveolar plateau (delta N2/L), as well as combinations of the two tests. While CV/VC is highly specific (92.3 percent in male and 94.0 percent in female subjects), it lacks sensitivity (36.8 percent in male and 13.3 percent in female subjects) and is abnormal in only 10.0 and 6.5 percent of male and female smokers, respectively, a percentage not dissimilar from the percentage with abnormal spirometry. However, delta N2/L, abnormal in 24.1 percent of male smokers and 28.8 percent of female smokers, rates reasonably well with regard to both sensitivity (63.2 percent in male and 66.7 percent in female subjects) and specificity (79.3 percent in male and 74.0 percent in female subjects). The group of smokers with abnormal delta N2/L did include fair numbers with abnormal spirometry (20.7 percent in male and 16.1 percent in female subjects). A combination of the two tests (abnormal in either delta N2/L and/or CV/VC) has good sensitivity (68.4 and 80.0 percent for male and female subjects, respectively) and specificity (74.3 and 69.0 percent for male and female subjects, respectively).

Chronic bronchitis and decreased forced expiratory flow rates in lifetime nonsmoking grain workers

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.