Air pollution and cytological changes in sputum.

The increase in sputum cellularity due to inflammatory and bronchial epithelial cells was compared in two groups of 308 and 399 subjects drawn from populations exposed to air-pollution levels common in industrialised countries. Single morning sputum specimens were examined and the differences in increased sputum cellularity between the two groups, stratified by age, sex, and tobacco consumption was assessed by the summary X2 test of Mantel-Haenszel. The group exposed to heavier air pollution had more increases in alveolar phagocytes, neutrophils, and lymphocytes, but not in eosinophils and bronchial epithelial cells. Subjects were also asked to answer a questionnaire on the symptoms of chronic bronchitis; the study showed that the inflammatory response preceded the appearance of symptoms.