Health risk associated with potential source regions of PM_2.5 in Indian cities

This paper estimates the regional contribution of high PM_2.5 concentration and associated mortality using HYSPLIT back trajectory analysis in eight Indian cities during 2015–2016. Health risk and mortality estimation were carried out using the Integrated Exposure Response function (IER) which was verified using our previous time series study in Delhi. Risk estimates from IER were observed to be slightly over-predicted (2.14%) when compared to health risk from time series study in Delhi. Health risk in the eight cities across the four seasons indicated higher chronic obstructive pulmonary disease (COPD), lung cancer (LC), ischemic heart disease (IHD), and stroke in the northern (COPD = 1.35, LC = 1.50, IHD = 1.39, Stroke = 2.06) and eastern cities (COPD = 1.27, LC = 1.38, IHD = 1.35, Stroke = 1.93) as compared to in southern or western cities. Risk of stroke was observed to be the highest: North = 1.37–1.52, South = 1.20–1.31, East = 1.40–1.52, and West = 1.24–1.35 times to that of other diseases. Uttar Pradesh was observed to be a major contributor to premature mortality in Delhi, Lucknow, and Patna accounting for 30, 71, and 42% of total premature death due to high PM_2.5 concentration during winter. Similarly, high PM_2.5 concentration from West Bengal and Bangladesh was responsible for 52% of total premature mortality in Kolkata while the Indian Ocean was a major contributor to premature mortality in western and southern cities during winter. Reduction of both local and regional pollution is required to yield a significant reduction in pollution of all cities except Delhi and Lucknow where regional and local sources respectively are dominant.