Examining the spatial and temporal variations in the indoor gaseous, PM_2.5, BC concentrations in urban homes in India

Given that people spend the majority of their time indoors, accurate measurement of pollutants in indoor environment settings is critical especially when the levels of air pollution often surpass those of outdoor environments. While extensive studies have been focussed on outdoor air quality, limited studies have examined indoor air quality in a residential setting. We measured gaseous and particulate pollutants using portable real-time monitors for similar to 24 h in indoor living spaces in dwellings, in urban slums in three metropolitan cities of India: Mumbai, Bangalore, and Delhi, and captured the pollutant levels from the domestic activities, which varied according to magnitudes and durations. The mean (+/- SD) of indoor total volatile organic compounds (TVOCs) and carbon monoxide (CO) were 720.1 (+/- 86.5) mu g/m(3) and 1.2 (+/- 0.3) ppm, respectively, for Mumbai; 626.1 (+/- 169.9) and 0.9 (+/- 0.5), respectively, for Bangalore; and 682.6 (+/- 251.8) and 1.7 (+/- 0.8), respectively, for Delhi. Particulate matter (PM2.5) and black carbon (BC) levels were 62.6 (+/- 16.9) and 3.2 (+/- 3.6), respectively, for Bangalore, and 187.7 (+/- 72.1) mu g/m(3) and 10.5 (+/- 3.3) mu g/m(3), respectively, for Delhi. Corresponding PM2.5 level in Mumbai were 111.2 (+/- 20.1) mu g/m(3). While high indoor levels of CO were associated with cooking, the use of incense and candles elevated CO and BC, cleaning activities increased TVOC and sweeping activities increased PM2.5. These levels are further affected by factors such as chimneys in homes (Mumbai-similar to 0.03%, Bangalore-similar to 15% and Delhi-similar to 37%), operating exhaust fans (Mumbai-similar to 35%, Bangalore-similar to 40% and Delhi-similar to 78%) and cross-ventilation characteristics (Mumbai-similar to 65%, Bangalore similar to 62% and Delhi-similar to 75%). Indoor concentrations excluding indoor activities, and outdoor concentration of CO (PM2.5) were found to be significantly correlated, similar to 0.51(0.40), 0.43(0.46) and 0.74 (0.68) for three cities respectively, which implies that outdoor air pollution is an important variable to consider when studying indoor air quality, especially during winter season where higher levels are observed in ambient environment.