Outdoor air pollution and emergency room visits at a hospital in Delhi

Several reports from large metropolitan cities have indicated significant association between acute morbidity and mortality from cardio-respiratory disorders and daily levels of major pollutants in the ambient air. Despite the wide-spread public concern about the adverse health effects of air pollution, there is substantial uncertainty regarding the effects of these pollutants at a concentration typical of Delhi, which is one of the ten most polluted cities in the world and the most polluted city in India. This study was undertaken to correlate the daily levels of various pollutants with the number of patients visiting the All India Institute of Medical Sciences (AIIMS, New Delhi) casualty for aggravation of certain defined cardiorespiratory disorders. Daily counts of patients visiting the emergency room of the AIIMS for acute asthma, acute exacerbation of chronic obstructive airway disease (COAD) and acute coronary event was obtained in prospective manner from January 1997 to December 1998. Daily mean levels of ambient CO, NOx and SO2 were monitored along with temperature and humidity. Data was analysed using one day time lag for events of interest. Time series analysis was undertaken using Poisson regression and population averaged general estimation equation, correcting for auto-correlation, days of the weak and season. The ambient levels of pollutants exceeded the national air quality standards on most of the days, over the two year period. Further, emergency room visits for asthma, COAD and acute coronary events increased by 21.30%, 24.90% and 24.30% respectively on account of higher than acceptable levels of pollutants. It is concluded that there is considerable burden of cardiorespiratory diseases in Delhi due to high levels of ambient air pollution.