Marked increase in sputum alveolar macrophages in residents of Calcutta: Possible exposure effect of severe air pollution

Air pollution is a major problem in Calcutta, In this study, exfoliated spu tum 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. 4 68 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/h pf) than that of rural controls (2.8/hpf, P < 0.001). Inflammatory cells li ke neutrophils and eosinophils were also found in increased numbers in the sputum of city dwellers. In the urban group, AM count was highest among res idents of north Calcutta where the pollution level was maximum and lowest i n the relatively less polluted south Calcutta, Similarly, pollution level a nd 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 person s. Since AM count is simple, non-intrusive and relatively inexpensive the r esults envisage usefulness of sputum AM count as an indicator of exposure t o ambient air pollution especially in large population-based studies in dev eloping countries.