Contrasting Patterns in Ambient PM_2.5 Exposure Disparity Across Population Subgroups in Urban and Rural India

Ambient PM_2.5 exposure poses the greatest environmental risk to public health in India. While several studies have quantified the changing patterns of exposure, the extent of inequality in exposure among population subgroups at the sub-national scale remains unknown. In this study, we examined the disparity in ambient PM_2.5 exposure across various population subgroups in urban and rural India and analyzed its changes in recent years by integrating satellite-derived PM_2.5 concentrations (1-km × 1-km) with sociodemographic information from the 4th (2015-2016) and 5th (2019-2021) rounds of the National Family Health Survey. We found a larger absolute disparity (60-90 µgm^-3) in high socio-demographic index (SDI) states compared to middle and lower SDI states. Moreover, we discovered that ambient PM_2.5 exposure was higher (indicated by relative disparities in terms of Z _score) among the top and bottom quantiles of wealth index and the other backward caste subgroup (Z _score > ±0.02, p < 0.1) than among their demographic counterparts in middle and high SDI states. From 2015-2016 to 2019-2021, the disparity in ambient PM_2.5 exposure across subgroups increased in urban areas, while it either remained static or decreased in rural areas. India's urban-centric approach to addressing air pollution may further exacerbate disparities among diverse demographics. Therefore, we recommend the formulation of targeted policies aimed at reducing ambient PM_2.5 exposure and alleviating disparities by prioritizing actions for the vulnerable subgroups.