Indoor PM2.5 in an urban zone with heavy wood smoke pollution: The case of Temuco, Chile

Abstract

Temuco is a mid-size city representative of severe wood smoke pollution in southern Chile; however,little is known about the indoor air quality in this region. A field measurement campaign at 63 householdsin the Temuco urban area was conducted in winter 2014 and is reported here. In this study, indoorand outdoor (24-hr) PM2.5 and its elemental composition were measured and compared. Infiltrationparameters and outdoor/indoor contributions to indoor PM2.5 were also determined. A statistical evaluationof how various air quality interventions and household features influence indoor PM2.5 was alsoperformed.This study determined median indoor and outdoor PM2.5 concentrations of 44.4 and 41.8 mg/m3,respectively. An average infiltration factor (0.62 ± 0.06) was estimated using sulfur as a tracer species.Using a simple mass balance approach, median indoor and outdoor contributions to indoor PM2.5 concentrationswere then estimated as 12.5 and 26.5 mg/m3, respectively; therefore, 68% of indoor PM2.5comes from outdoor infiltration. This high percentage is due to high outdoor pollution and relatively highhousehold air exchange rates (median: 1.06 h1).This study found that S, Br and Rb were dominated by outdoor contributions, while Si, Ca, Ti, Fe and Asoriginated from indoor sources. Using continuous indoor and outdoor PM2.5 measurements, a medianindoor source strength of 75 mg PM2.5/min was estimated for the diurnal period, similar to literatureresults. For the evening period, the median estimate rose to 135 mg PM2.5/min, reflecting a more intensewood burning associated to cooking and space heating at night.Statistical test results (at the 90% confidence level) support the ongoing woodstove replacementprogram (reducing emissions) and household weatherization subsidies (reducing heating demand) forimproving indoor air quality in southern Chile, and suggest that a cookstove improvement programmight be helpful as well.