The oxidative potential of PM_(2.5) exposures from indoor and outdoor sources in rural China

摘要

Background: Airborne paniculate matter (PM) is a widespread environmental exposure and leading health risk factor. The health effects of PM may be mediated by its oxidative potential; however, the combustion and non-combustion sources and components of PM responsible for its oxidative potential are poorly understood, particularly in low- and middle-income rural settings where coal and biomass burning for cooking and heating contribute to PM exposure. Methods: We measured 24-h personal exposures to fine paniculate matter (PM_(2.5)) of 20 rural women in northern (Inner Mongolia) and southern (Sichuan) Chinese provinces who used solid fuels (i.e., coal, biomass). PM_(2.5) exposures were characterized for mass, black carbon, water-soluble organic carbon, major water-soluble ions, and 47 elements. The oxidative potential of PM_(2.5) exposures was measured using acellular (dithiothreitol-based) and cellular (macrophage-based) assays. We performed factor and correlation analyses using the chemical components of PM_(2.5) to identify sources of exposure to PM_(2.5) and their chemical markers. Associations between oxidative potential and chemical markers for major sources of PM_(2.5) exposure were assessed using linear regression models. Results: Women's geometric mean PM_(2.5) exposures were 249 ug m~3 (range: 53.9-767) and 83.9 ug m~3 (range: 73.1-95.5) in Inner Mongolia and Sichuan, respectively. Dust, biomass combustion, and coal combustion were identified as the major sources of exposure to PM_(2.5). Markers for dust (iron, aluminum) were significantly associated with intrinsic oxidative potential [e,g., one interquartile range increase in iron (ppm) was associated with an 85.5% (95% Cl: 21.5,149) increase in cellular oxidative potential (ug Zymosan mg~(-1))], whereas markers for coal (arsenic non-sulfate sulfur) and biomass (black carbon, cadmium) combustion were not associated with oxidative potential. Conclusions: Dust was largely responsible for the intrinsic oxidative potential of PM_(2.5) exposures of rural Chinese women, whereas biomass and coal combustion were not significantly associated with intrinsic oxidative potential.