Air Pollution and Health in Delhi, India: Health Effects of Short-Term Exposures and Policy Implications

Abstract

Air pollution exposure is recognized as an important contributor to premature mortality and morbidity globally. Exposure to ambient particulate matter smaller than 2.5 microns in aerodynamic diameter (PM2.5) has been associated with all-cause and non-accidental mortality, cardiovascular and respiratory diseases, premature births and birth defects, and neurocognitive deficits, among other conditions. India is home to some of the most polluted cities on the planet, the chief among them being Delhi. Ambient air pollution (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, contributing to a large and preventable burden of diseases. While air quality has worsened in Delhi over the last two decades, action to reduce emissions from polluting sources has been scarce at best. This lack of action has been teamed with pushback against most epidemiological evidence published in the last few years showcasing the harmful effects of air pollution in Delhi and in India.

To address the dual gaps in locally generated evidence, and level of trust in this evidence among various key stakeholders, this project aimed to: • Generate local evidence on the short-term impacts of PM2.5 exposures on non-accidental mortality • Translate that evidence for a diverse set of stakeholders including policymakers, the media, and the general public

Utilising mortality data obtained from the municipal government of Delhi for the period June 2010-December 2016, I conducted epidemiological analyses to understand these associations. I found that each 25 µg/m3 increment in daily PM2.5 exposure was associated with a 0.8% (95% CI: 0.3, 1.3%) increase in daily non-accidental mortality in the study population and a 1.5% (95% CI: 0.8, 2.2%) increase in mortality among those aged 60 or over. The exposure-response relationship was non-linear in nature, with relative risk rising rapidly before tapering off above 125 µg/m3. Meeting WHO guidelines for safe levels of exposure over the study period would have averted 17,526 (95% CI: 6837, 25589) premature deaths, with older and male populations disproportionately affected.

The findings of this study are highly relevant for policy as Delhi and India move forward to reform environmental regulations governing air quality. Over the course of the project, I have also formulated a translation and dissemination strategy that will aid in simplifying the complex epidemiological findings of this study for key stakeholders, in addition to building trust in the process of evidence generation among decision-makers. By engaging through the entire paradigm of research to policy, I hope to better inform otherwise antagonistic or agnostic policymakers, raise awareness among those most affected by air pollution exposure in Delhi, and aid citizens to more effectively advocate for their right to clean air in one of the most polluted cities on the planet.