The prevalence of acute and chronic respiratory symptoms and diseases as well as ventilatory capacity were studied in 806 workers without occupational exposure to air pollutants. The established prevalence of chronic respiratory symptoms was similar to that found in the general pollution. It was also higher in smokers than in non-smokers. Relatively a very small number of workers (only smokers) complained of acute symptoms during work shift. The measured ventilatory capacity values were not significantly different from the predicted values. There was a significant increase in all ventilatory capacity values during work shift (FVC, FEV1, FEF50, FEF25) which varied from +1.9 to 9.8% of the preshift values. In older workers (>40 years of age) as well as in those with longer exposure (<40 years) and those with shorter employment (<10 years). Smoking habit appears to be the major factor responsible for the development of lung impairment in workers not exposed to atmospheric pollution.