Marked increase in sputum alveolar macrophages in residents of Calcutta: Possible exposure effect of se- vere air pollution

Air pollution is a major problem in Calcutta. In this study, exfoliated sputum cytology of the exposed population was done in order to get an insight into the response of the lungs to air pollutants at the individual level. 468 residents from Calcutta and 60 from Sunderban islands, where ambient air pollution is negligible, were studied. Results showed remarkable increase in alveolar macrophage (AM) number in the sputum of the urban group (22.7/hpf) than that of rural controls (2.8/hpf, P < 0.001). Inflammatory cells like neutrophils and eosinophils were also found in increased numbers in the sputum of city dwellers. In the urban group, AM count was highest among residents of north Calcutta where the pollution level was maximum and lowest in the relatively less polluted south Calcutta. Similarly, pollution level and AM count were maximum during the winter, minimum during the monsoon and intermediate in summer. Thus, a close parallelism was observed between the magnitude of air pollution and the AM count in sputum of the exposed persons. Since AM count is simple, nonintrusive and relatively inexpensive the results envisage usefulness of sputum AM count as an indicator of exposure to ambient air pollution especially in large populationbased studies in developing countries.