China is conducting a large-scale replacement of high-polluting, traditional heating stoves in rural areas with electricity- and natural gas-powered clean heating systems due to the contribution of residential coal combustion to air pollution. We conducted a feasibility study among 300 households in three districts in the Beijing Municipality Region to collect baseline information on heating technologies and usage patterns, housing characteristics, and indoor air pollution. In each district, one treatment village (coal restricted and access to heat pump replacement program) and a similar non-treatment village (not coal-restricted and no access to heat pump replacement program) were selected. We measured 24-h indoor concentrations of fine particulate matter (PM2.5, 5-min resolution) in a subset of homes in each village (n = 4-6 homes per village) using a laser photometer (DustTrak 8520, TSI Inc, measurements corrected for known light-scattering bias). Hourly outdoor PM2.5 concentrations were obtained from the nearest environmental air quality monitoring stations in each district, and used to calculate hourly ratios of indoor-to-outdoor (I/O) PM2.5, as a means to initially investigate the influence of outdoor and indoor sources of PM. Our preliminary results suggested that the subsidized clean heating technologies replaced coal in 2 of the 3 treated villages and were associated with lower indoor PM2.5 concentrations. In the 2 treated villages that stopped using coal, geometric mean (95% CIs) 24-h indoor concentrations of PM2.5 were non-significantly lower compared with untreated homes in the same district [geometric mean [treated: 162 (85,307) u.g/m3 vs. un-treated: 222 (141,351) μg/m3]. We also found that the average hourly I/O PM2.5 ratios were lower in treated homes compared with untreated homes in the same district [treated: 2.7 (1.4, 5.0) vs. un-treated: 3.9 (2.7, 5.5)], suggesting that indoor sources may contribute less to measured indoor PM2.5 in these homes.
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