Abstract
Mitigating the impact on human health worldwide is important to mitigate the morbidity and mortality arising from its exposure. The level and type of pollutants vary in different urban and rural settings. Here, we explored the extent of air pollution and its impacts on human health in megacity Delhi (India) through the review of published literature. The study aims at describing the extent of air pollution in Delhi, the magnitude of health problems due to air pollution and risk relationship between air pollution and associated health effects. We found 234 published articles in the PubMed search. The search showed that the extent of air pollution in Delhi was described by various researchers from about 1986 onwards. We synthesised the findings and discussed at length with respect to reported values, their possible interpretations and any limitations of the methodology. The chemical composition of ambient air pollution is also discussed. Further, we discussed the magnitude of health problem with respect to Chronic Obstructive Pulmonary Diseases (COPD), bronchial asthma, and other illnesses. The results of the literature search showed that data has been collected in last 28 years on ambient air quality in Delhi, though it lacks a scientific continuity, consistency of locations and variations in parameters chosen for reporting. As a result, it is difficult to construct a spatiotemporal picture of air pollution status in Delhi over time. The number of sites from where data have been collected varied widely across studies and methods used for data collection is also non-uniform. Even the parameters studied are varying, as some studies focused on PM10 and PM2.5, some of the suspended particulate matter (SPM) and respirable suspended particulate matter (RSPM). Similarly, the locations of data collection have been widely varied. Some of the sites were at busy traffic intersections, some on the terrace of offices and residential houses and others in university campus or airports. As a result, the key question of the extent of pollution and its distribution across various parts of the city cannot be inferred. None of the studies or a combination of it could present a complete picture of the burden of diseases like COPD, bronchial asthma and other allergic condition attributable to pollution in Delhi. Neither it could be established that what fraction of the burden of above diseases is attributable to ambient air pollution, given that other factors like tobacco smoke and indoor air pollution are also contributors to the causation of such diseases. In our discussion, we highlighted the knowledge gaps and in the conclusion, we suggested what research can be undertaken to fill the existing knowledge gaps.