Characteristics of indoor and personal exposure to particulate organic compounds emitted from domestic solid fuel combustion in rural areas of northwest China

Household solid fuel combustion for heating in winter is a substantial source of air pollution in rural areas of northwest China. The present study investigated the concentration characteristics and health risks of particulate matter (PM) and its organic compounds, including polycyclic aromatic hydrocarbons (PAHs), oxygenated PAHs (OPAHs), and phthalate esters (PAEs). Indoor air and housewives' personal exposure (PE) samples were collected in Guanzhong Basin, among rural households relying on various solid fuels for heating in winter. Indoor PM primarily comprised fine PM (PM₂.₅, 76%), and its organic compounds were identified in particular abundance in households that used coal as the only domestic fuel (Group C, 96% in PM₂.₅). The mean concentration of PE to PM₂.₅ was 307 ± 120 μg·m⁻³, which was 2.4-times higher than the indoor concentration (130 ± 103 μg·m⁻³) because of the housewives' short-term exposure to high-concentration pollution emitted by solid fuel combustion. Organic compounds exhibited the same pattern, with PE samples having a 44% higher concentration than indoor samples. The correlation of PM₂.₅-bound organics between indoor and PE samples in Group C (R² = 0.9) was higher than that in the group using coal and biomass (Group M, R² = 0.6), indicating the stronger correlation of single-fuel heating method. The PE/indoor ratio of high molecular weight (HMW) PAHs in Group C (2.5) was higher than that of the other organic compounds (1.3) because HMW PAHs emitted through coal combustion had a larger effect on PE. This further led to higher incremental lifetime cancer risks (ICLRs) via inhalation pathway among housewives in Group C (2.4- and 1.2-times higher risk for PAHs and PAEs, respectively) than among those in Group M. However, inhalational ILCR values of Group M were still 2.1–340-times higher than the international safety standard (10⁻⁶). Therefore, the upgradation of domestic fuels and heating ways is urgently needed in rural area of northwest China to reduce indoor air pollution and health risks.