Long-term atmosphere surveillance (2017-2022) of PM2.5‑bound polycyclic aromatic hydrocarbons and health risk assessment in a typical city in northern China.
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OBJECTIVE: By analyzing the pollution characteristics of polycyclic aromatic hydrocarbons (PAHs) in PM2.5 in the atmosphere of Hohhot City, we can assess their main sources and evaluate their health hazards. METHODS: From 2017 to 2022, atmospheric PM2.5 sampling was conducted in Hohhot City. The content of PAHs in the PM2.5 samples was determined using high-performance liquid chromatography. To analyze the sources of PAHs, molecular diagnostic ratios and positive matrix factorization were initially employed to quantify potential PAH sources. Subsequently, the Potential Source Contribution Function was used to analyze the potential emission source areas of PAHs. The recommended health risk assessment model by the United States Environmental Protection Agency was utilized to calculate the lifetime excess cancer risk associated with exposure to PAHs. RESULT: From 2017 to 2022, the levels of PM2.5 and PAHs showed a decreasing trend year by year, decreasing from 40 μg/m3 to 20 μg/m3 and from 6.92 ng/m3 to 3.60 ng/m3, respectively. The rate of PM2.5 exceeding the Chinese Grade I standard (35 μg/m3) decreased from 65.77% to 24%, and the rate of benzo[a]pyrene concentration exceeding the standard limit (2.5 ng/m3) was 23.88%. Through molecular diagnostic ratios and positive matrix factorization analysis, it was found that biomass/coal combustion (cumulative contribution rate of 56.77%) and traffic emissions (cumulative contribution rate of 36.94%) were the main sources of pollution. The potential pollution source areas in Hohhot City were mainly distributed in Mongolia, western Inner Mongolia, and neighboring provinces and cities. The median incremental cancer risks for children and adults with long-term exposure to PAHs were 5.14 × 10-7 and 1.68 × 10-7, respectively. CONCLUSION: The overall pollution situation of PM2.5 and PAHs in Hohhot City can be considered acceptable, but it is important to pay attention to pollution sources such as combustion and traffic emissions. The potential pollution source areas are relatively widespread, but the cancer risk remains within an acceptable level.