Daily mortality associated with short-term PM2.5 exposures in Delhi, India

Abstract

Daily mortality associated with short-term PM2.5 exposures in Delhi, IndiaINTRODUCTION: Ambient PM2.5 levels in Delhi routinely exceed World Health Organization (WHO) guidelines and Indian National Ambient Air Quality Standards (NAAQS) for safe levels of daily exposure (1). While a number of studies are currently underway to examine the association of chronic exposures to respiratory and cardiovascular outcomes (2-4), only two have examined the short-term effects of exposure to high levels of PM on mortality in Delhi, and none with PM2.5 as the exposure of interest (5,6).AIM: We aimed to analyse the association between short-term PM2.5 exposures and all-cause mortality in Delhi, India.METHODS: Using generalized additive poisson regression models, we examined the association between 2-day moving average PM2.5 exposures against all-cause mortality data in the period between June 2010 and December 2016. Daily exposures to PM2.5 are estimated using an ensemble averaging technique developed by our research group, and mortality data were obtained from the Municipal Corporations of Delhi (North, East and South), and the New Delhi Municipal Council, altogether comprising 97-99% of all deaths recorded in Delhi each year during that time period.RESULTS: Median 2-day moving average exposure to PM2.5 were 91.2 µg/m3 (IQR: 70.4, 127.8), with minimum and maximum exposures of 27.3 µg/m3 and 637 µg/m3 respectively. 948,440 deaths were recorded in Delhi during the stated time period. Each 25 µg/m3 increment in exposure was associated with a 0.3% (95% CI: 0.03, 0.7%) increase in all-cause mortality. The dose-response relationship was non-linear in nature, with relative risk tapering off above 500 µg/m3.CONCLUSION: This study adds to the growing body of local evidence on air pollution and health, with implications for short-term and long-term policy to mitigate exposures in a megacity that is home to over 18 million.