Distribution, sources, and health risks of PM_2.5 and PM₁-bound polycyclic aromatic hydrocarbons in the Pearl River Delta

Polycyclic aromatic hydrocarbons (PAHs) can be adsorbed onto particulate matter (PM) in the atmosphere. However, few studies have profiled and compared the distribution, sources, and health risks of PAHs associated with smaller particle sizes (i.e., PM₁ and PM_2.5). To address this gap, we collected ambient PM_2.5 and PM₁ samples from 89 schools across six cities in the Pearl River Delta region of Guangdong province, China, during April to June and October to December 2018. We characterized 18 PM-bound PAHs by means of gas chromatography-mass spectrometry. Diagnostic ratios and positive matrix factorization (PMF) were employed to identify source apportionment. We assessed the health risks of PAHs via incremental lifetime cancer risk (ILCR), carcinogenic loss of life expectancy (LLE), and non-carcinogenic hazard index (HI). Results showed that, in monitoring cities, the average concentration of 18 PM_2.5-bound PAHs was 6.75 (range: 1.26–24.8) ng/m³ in winter and 3.59 (range: 0.6–16.3) ng/m³ in summer, while PM₁-bound PAH concentration in winter was 5.39 (range: 1.05–21.9) ng/m³. High-molecular-weight PAHs predominated, with elevated levels observed in winter and in the central and western regions, particularly in PM₁ samples. The primary source of PM-bound PAHs was petroleum combustion, mainly attributed to vehicle exhausts. Health risk assessment indicated that carcinogenic toxicity did not show significant differences between PM_2.5 and PM₁-bound PAHs. Finally, our study expands the existing knowledge of PM_2.5 and PM₁-bound PAH contamination in the atmospheric environment.