Objective To reveal the spatiotemporal distribution patterns, source apportionment, and health risks of polycyclic aromatic hydrocarbons (PAHs) in fine particulate matter (PM_2.5) in Baotou city, and to provide data support for precise regional air pollution control.

Methods From 2020 to 2024, continuous sampling and monitoring were conducted. High-performance liquid chromatography, diagnostic ratio analysis, and positive matrix factorization were employed to systematically analyze the spatiotemporal distribution patterns, pollution sources, and human health risks of PAHs.

Results During the monitoring period, the concentrations of PAHs decreased significantly, with an average annual decrease of 8.6% (P < 0.05). The concentrations of 4-6 ring PAHs in the heating season (first and fourth quarters) were still 3-5 times those in the non-heating season (P < 0.001). Positive matrix factorization-based source apportionment indicated that coal combustion and biomass burning were the main sources (57.7%), followed by vehicle exhaust (31.3%) and petroleum evaporation (11.0%). Health risks showed significant seasonal differences, with higher risk entropy in winter and spring than in summer and autumn. The carcinogenic risk of benzoapyrene, a key carcinogen, decreased significantly by 54.2% from 2.4×10^-6 to 1.1×10^-6, but it was still the only component exceeding the acceptable level of 1×10^-6, and its carcinogenic risk should not be ignored.

Conclusion The PAHs pollution in Baotou exhibits typical characteristics of the energy consumption structure, marked by significantly elevated PAHs concentrations during the heating season with the four to six ring homologues dominating the profile.