Effects of smoking on pulmonary function and symptomatology in occupationally exposed groups.

Records of 3006 employees of nine companies in southeast Texas screened by a local lung association during the years 1974-1975 were examined to assess the effect of smoking, age, and occupational and residential ambient air pollution exposure. The effects of smoking and occupational exposure were strong when tested against a respiratory morbidity response questionnaire considered to be diagnostic for early-stage bronchitis. Occupational exposure lost statistical significance after place of residence was controlled in the analysis. Smoking and age variables exhibited significant effects when the response variable was pulmonary function test results. The differences between questionnaire and pulmonary function test results may indicate early-stage vs. later-stage respiratory morbidity ascertainment. Agreement in classifying "abnormal" subjects with these two methods decreased with increasing levels of smoking.