Substantially underestimated health burden of Indian road transportation air pollution

Road transportation is a major contributor to multiple health-harming air pollutants in India, but exclusive focus on fine particulate matter (PM2.5) pollution and premature mortality along with reliance on global emission inventories that lack detailed national information has undermined contribution of this sector. Here, we examine the influence of Indian road transportation on air pollution and public health using the global Community Emissions Data System (CEDS) emissions inventory and the recently developed national Air Quality, Emission Inventory and Modelling (AEIM) inventory for 2019. The AEIM inventory uses high-resolution activity data and technology-specific emission factors to accurately represent the realistic magnitude and spatial heterogeneity in road transportation emissions across India. Both inventories are used to drive the state-of-art atmospheric chemistry model GEOS-Chem at high spatial resolution (~30 km), and AEIM outperforms CEDS when compared to the quality-controlled ground-based observations from India’s extensive air quality monitoring network. We find that CEDS road transportation emissions are linked to population-weighted mean concentrations (or exposures) of 3.3 µg m-3 of PM2.5, 1.4 ppb of nitrogen dioxide (NO2), and 3.5 ppb of maximum daily 8-hour running-mean ozone (MDA8 O3), the metric associated with health risk. Exposures using the robust AEIM inventory are 66-223% higher: 10.6 µg m-3 of PM2.5, 4.0 ppb of NO2, and 5.8 ppb of MDA8 O3. While road transportation PM2.5 is highest in the Indo-Gangetic Plain, we find that contribution of road transportation to other health-harming pollutants is not necessarily co-located. NO2 hotspots are over major cities and transportation corridors and those for MDA8 O3 are in central and south India, indicating additional health burdens in these regions. Using the AEIM-driven model output and considering diverse pollutants and health impacts, we estimate 10.8 million disability adjusted life years (DALYs) from road transportation-related air pollution in India, five times that associated with previously estimated CEDS-driven road transportation PM2.5 mortality and exceeding that attributed to cigarette smoking in India by 27%. Uttar Pradesh in the Indo-Gangetic Plain has the greatest health burden across all adverse outcomes but the rankings for other states vary by pollutants and health outcomes. Our assessment not only quantifies the magnitude of underestimation but also highlights states that emerge as key contributors to the health burden, providing actionable insights for evidence-based mitigation strategies.Funded by the UKRI-NSF Clean Energy and Equitable Transportation Solutions (CLEETS) project.