PM2.5 exposure in highly polluted cities: A case study from New Delhi, India.

Personal exposure (PE) to air pollutants is driven by a combination of pollutant concentrations in indoor and outdoor environments, and time-activity pattern of individuals. The objectives of this study were to estimate personal exposure to PM2.5 and black carbon (BC), and assess the representability of ambient air quality monitoring stations to serve as surrogates for PE in New Delhi. Personal exposure to air pollutants (PM2.5-PE and BCPE) was measured using portable, battery-operated instruments (PM2.5- pDR1500 and BC- microAethalometer AE51) in a small cohort of healthy adults (n=12 in summer, n=6 in winter) with no occupational exposure. Average PM2.5-PE and BCPE (µg/m3) were 53.9±136 and 3.71±4.29 respectively, in summer and 489.2±209.2 and 23.3±14.9 respectively, in winter. Activities associated with highest exposure levels were cooking and indoor cleaning for PM2.5, and commuting for BC. Within transport microenvironments, autorickshaws were found to be the most polluted, and lowest BC exposure was registered in public buses. Comparison of fixed-site ambient monitoring data showed a higher correlation with personal exposure dataset in winter compared to summer (r2 of 0.51 (winter) and 0.21 (summer); 51% (winter) and 20% (summer)). This study highlights the need for detailed assessment of PE to air pollutants in Indian cities, and calls for a denser network of monitoring stations for better exposure assessment.