Assessment of Household Air Pollution

Concentrations of air pollution from cooking fuels, secondhand tobacco smoke (SHS), and other pollution sources were measured in all participating households using structured questionnaires and objective measures of PM_2.5.

All questionnaires were translated into Marathi to ensure that subjective questions would be asked in a standardized way, with response options that were clear to the participants, and to ensure that they were true to their intention. Questionnaires were first translated into Marathi and then back-translated into English. Discrepancies were identified, and further edits were made by study team consensus. Questionnaires assessing factors both in the home and outside the home that may affect household PM_2.5 concentrations were administered to each participant at the baseline visit. Participants were asked about the types of fuel used in the home and typical use of these fuels over the past 7 days. After 24 hours, study staff returned to the home and information was collected on concentration determinants over the previous 24 hours. Information on ventilation was collected by asking participants whether they opened doors or windows when cooking. Additional collected information included trash burning near the home, proximity to neighbors using wood for cooking, exposure to SHS, and/or regular preparation of Mishri (a smokeless tobacco product prepared by burning). Questions regarding neighbors using wood for cooking and the preparation of Mishri were added after data collection began, and thus data exists for only a subsample of participants. Participants also reported the use of mosquito coils, incense, and candles or kerosene for lighting. Details of the housing construction and ventilation were recorded by observation. This included information on household characteristics such as construction materials of the walls, roof, and floor, the presence of a gap between the ceiling and the roof, the presence of a separate kitchen, and the size of the cooking space.

Real-time household PM_2.5 concentration was assessed using the Thermo Environmental Instruments pDR-1000 (Thermo Fisher Scientific, Waltham, MA) fitted with a cyclone inlet (BGI, Waltham, MA) and paired with portable constant-flow pumps (SKC Inc, PA). Pumps were pre- and post-calibrated at 4 L/min using a Bios DryCal primary flow calibrator (MesaLabs, Lakewood CO). A pre-weighed Teflon filter was placed downstream in pre-loaded cassettes for gravimetric measurements. The monitoring set-up was placed approximately 1 × 1 meter away from the primary cook stove in each home. In addition to the integrated 24-hr gravimetric filterbased measurement, the pDR-1000 recorded nephelometric-based measurements of PM_2.5 concentration every minute for the 24-hour period. Filters were post-weighed to assess a 24-hr time-weighted-average (TWA) concentration over the sampling period. The ratio of the TWA nephelometric and the corresponding gravimetric-based TWA concentrations was used as a calibration factor to conver real-time pDR-derived concentrations to gravimetric-equivalent concentrations(21). Blank filters were included for quality control purposes at 10% of the home visits.