Long-term exposure to fine particulate matter (PM2.5) is a global public health concern linked to increased mortality and morbidity. The Global Burden of Diseases (GBD) 2019 study attributed 0.98 million deaths in India to ambient air pollution. However, the exposure-response functions used in such assessments are often derived from countries with much lower air pollution levels, potentially misrepresenting the risks in India.
India experiences some of the highest levels of air pollution globally, with a population-weighted mean PM2.5 exposure of 57.3 µg/m³ from 2000 to 2019, far exceeding the revised annual mean guideline of not >5 µg/m³ recommended by the World Health Organization (WHO). Despite these high levels, there is limited evidence linking long-term PM2.5 exposure to mortality in India, and most existing studies rely on exposure-response functions from lower-exposure countries. The inadequacy of these models for the Indian context highlights the need for locally-derived data to better shape the development of public health policies. Previous studies from India have focused on cause-specific and premature mortality or on non-causal methods, which may not fully capture the health risks associated with PM2.5.
A recent study published in the “Lancet” aimed to provide robust, India-specific evidence on the association between long-term PM2.5 exposure and all-cause mortality using a causal inference method, specifically a difference-in-differences approach. Using a quasi-experimental design, this study showed an increased mortality risk from long-term exposure to PM2.5, highlighting the need to frame tighter regulatory frame work to decrease the emissions and reduce the mortality across India and protect the public health (see the Graphic).
(Source: Jaganathan S, Stafoggia M, Rajiva A, Mandal S, Dixit S, de Bont J, Wellenius GA, Lane KJ, Nori-Sarma A, Kloog I, Prabhakaran D. Estimating the effect of annual PM2· 5 exposure on mortality in India: A difference-in-differences approach. The Lancet Planetary Health. 2024; 8(12):e987-96. Doi: 10.1016/S2542-5196(24)00248-1)