Spatiotemporal variation of particulate matter & risk of exposure in the indoor-outdoor residential environment: a case study from urban city Delhi, India

Humans spend close to 90% of their time within the indoor environment. Deteriorating indoor air quality, especially high PM10, PM2.5 and PM1 is slowly becoming a major concern. A study was carried out, for two years, to characterize the spatiotemporal variation of PM in the indoor-outdoor environment across different residential setups (R1, R2, R3, and MC) in the Delhi region. The study established correlation between monthly variations of Indoor/Outdoor (I/O) ratios and meteorological factors. The results showed Spatio-temporal variation in the average mass concentrations of PM10 recorded peak values during the winter season (avg. 514± 72.15 µg/m3) and minimum concentration was observed during monsoon (avg. 91.41± 22.64 µg/m3) months. Among all the sites, the mixed cluster (MC), a residential cum commercial zone reported the highest particulate matter concentration (avg. 308.10 ±37.23 µg/m3) and while R2 reported the least concentration (avg. 244.9± 27.65 µg/m3) within the indoor environment. The I/O ratios of particulate matter were observed to be highest in January (I/O ratio1.6) and lowest in June month (I/O ratio 0.8). PM10, PM2.5, and PM1 dynamics were found to be critically influenced by meteorological factors, regular household activities, and diverse building designs. The short- or long-term exposure of particulate pollutants (beyond the permissible limits) can increase the probability of acute health effects, so there is an utmost requirement to collect better and systematic information about actual exposure levels experienced in different urban residential environments.