Fine Particle (PM2.5) Composition of Indoor and Outdoor Air Samples Collected in Xuanwei County, China

Abstract

Indoor air pollution is a cause of many adverse health outcomes especially in developing countries where high levels of pollutants are generated by burning solid fuels for cooking and heating purposes. In China, the lung cancer rates are highest in Xuanwei County and the burning of coal in the home is thought to be a primary cause -- especially among women who are generally responsible for domestic cooking activities and have low smoking rates. Fine particulate matter (PM2.5) samples were collected in Xuanwei County during the launch of an epidemiological study investigating the relationship between birth outcomes and PM2.5 exposure in collaboration with Kunming Medical University. PM2.5 was measured in nine households across three villages for three consecutive days. At each home, two 12-hr samples (approximating daytime and nighttime periods) were collected indoor concurrently with a 24-hr outdoor measurement. Continuous fine particle sampling was also conducted indoors using a low-cost particle sensor. Samples were analyzed for total PM2.5 mass concentration and selected components (levoglucosan, 1-nitropyrene, and benzo[a] pyrene) indicative of source and potential carcinogenicity. Concentration of PM2.5 mass and selected components varied considerably between time periods sampled indoors (daytime range 25.2 – 4371 µg/m3; nighttime range 21.7 – 156 µg/m3) and between indoor and outdoor compartments (indoor range 23.4 – 2264 µg/m3; outdoor range 16.4 – 41.1 µg/m3). Continuous PM2.5 particle monitoring confirmed the episodic nature of the fine particle generation with peaks observed mainly during typical hours of cooking activities. None of the outdoor samples were above Chinese regulatory standards for ambient air quality. Several indoor concentrations of PM2.5 were well above recommended WHO guidelines and benzo[a]pyrene (BaP) concentrations were above Chinese National Criteria standards. Future studies may benefit from longitudinal sampling to assess temporal variations that may exist within households, particularly those that have choices in cooking and heating fuels.