Assessment of Indoor and Outdoor PM2.5 in Slums of Mumbai, India

Abstract

Background/Aim: Mumbai slums, which house more than 50% of the city’s population could be at a higher risk of air pollution due to its proximity to major outdoor air pollution sources, poor ventilation and presence of indoor emission sources. The aim of this study is to measure and model the indoor air pollution exposures of Mumbai slum population vis-a-vis the outdoor levels. Methods: Household questionnaire survey having demographic, indoor source activity, ventilation and respiratory health symptoms was conducted in 500 randomly selected homes of seven slums in Mumbai to identify possible sources and factors affecting indoor air pollutants’ exposures. In two of the slums, inside 10 homes each, 24-hour indoor gravimetric PM2.5 monitoring was also conducted. Results: Significant number of homes are poorly ventilated (~90% homes with no cross ventilation) and experience overcrowding (~30% homes with ≥ 4 person/room). >50% kitchens have no separation from the living rooms. Mean PM2.5 concentrations are 39 ± 17 µg/m3 indoors and 23 ± 4 µg/m3 outdoors. The in/out PM2.5 ratio ranged from 0.9 to 3.7, higher than the values observed in non-slum homes. Frequent brief excursions are observed in indoor PM2.5 and BC, which are 2-3 times higher than the median concentrations, during cooking activities. Multivariate linear regression analysis shows proximity to the major traffic roads and separation of the kitchen from adjacent living rooms as the most dominant determinants of the indoor PM2.5 exposures. Additional indoor PM2.5 monitoring in ~80 homes in these slums is currently underway which will be used for developing models for predicting indoor PM2.5 exposures. Conclusions: Indoor PM2.5 exposures in poorly ventilated homes in slums of Mumbai seem to be driven largely by outdoor road traffic emissions as well as indoor activities such as cooking.