Sequential health effect study in relation to air pollution in Bombay, India.

A health study done for 4 years in 4129 subjects from 3 urban (high, medium and low according to SO2 levels) and a rural community showed a higher morbidity with raised levels. Initially in the respective 4 areas standardised prevalences (in percent) were: for dyspnoea 7.3, 6, 3.2 and 5.5; for chronic cough 5.1, 2.7, 1.7 and 3.3; for intermittent cough 15.6, 5.8, 0.4 and 3.7 and frequent colds 18.0, 20.8, 12.1 and 11 percent. The diagnosis of chronic bronchitis was done in 4.5, 4.5, 2.3 and 5.0 percent and cardiac disorders 6.8, 4.3, 8.2 and 2.7 percent in respective 4 areas. After 3 years, 55-60% of urban and 44% of rural subjects were reassessed. Several minor symptoms, besides above ones were related closely to the urban air pollutant profile. Increased greenery protected only at lower levels of pollution. Initial lung functions were best in "urban low" area but in all urban areas, yearly declines were larger than in rural subjects. A cross sectional study for effect of slums in 4 areas on 22272 subjects revealed generally higher morbidity in slum residents, particularly in "urban medium" area for frequent colds, cough and dyspnoea. Daily health diaries maintained in 2232 subjects revealed high morbidity in 2 more polluted areas; monthly trends correlated to SO2 and S.P.M. and daily fluctuations with SO2 revealed a threshold between 50 to 100 micrograms/CM/day. There were greater mortality (S.M.R.) in cardiorespiratory and malignant diseases related to pollution. The major factors affecting morbidity were pollution, nutrition, occupation, smoking and age.