Molecular characterization, source apportionment, and health risk assessment of particulate-bound polyaromatic hydrocarbons (PAHs) and their nitro and oxy-derivatives in Agra, India.
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Despite the recognized carcinogenic and mutagenic potency of nitrated (NPAHs) and oxygenated (OPAHs) PAH derivatives, their ambient occurrence remains underexplored compared to parent PAHs (pPAHs). This is the first study to present a comprehensive evaluation of particulate-bound polycyclic aromatic compounds (PACs)-16 pPAHs, 13 NPAHs, and 9 OPAHs-in Agra, focusing on seasonal variability, emission sources, and associated carcinogenic risks. The particulate samples collected from November 2023 to June 2024 were analyzed using gas chromatography-mass spectrometry (GC-MS). Mean concentrations of ∑16pPAHs, ∑13NPAHs, and ∑9OPAHs were 66.1 ± 16.2, 96.5 ± 29.2, and 154.2 ± 90.4 ng m-3, respectively, with OPAHs exhibiting the highest abundances. Seasonal variations revealed winter peaks for pPAHs and NPAHs, whereas OPAHs exhibited a pronounced summer peak driven by secondary formation. The NPAH profile was dominated by 3-Nitrofluoranthene (3-NFla), 1-Nitropyrene (1-NP), 9-Nitroanthracene (9-NAnth), and 2-Nitronapthalene (2-NNaP), whereas OPAHs demonstrated compound-specific behaviour, with 9-Fluorenone (9-FluO) enriched in winter and 9,10-Phenanthraquinone (9,10-PQN) markedly elevated in summer, reflecting photochemical oxidation processes. Source apportionment identified fossil fuel combustion (41.3 %), vehicular emissions (34.5 %), oil combustion (14.9 %), and secondary formation (9.3 %) as major contributors. Incremental lifetime cancer risk (ILCRtotal) values exceeded the United States Environmental Protection Agency (USEPA) threshold for children (0-3 yrs) and adults (18-45 yrs), indicating potential carcinogenic risk. Total Benzo(a)Pyrene Equivalents (TEQBaP) values for Benzo(a)Pyrene (BaP), Dibenz(a,h)anthracene (DbA), and 1-NP surpassed World Health Organisation (WHO) guidelines, emphasizing the toxicological relevance of PAH derivatives and the need for their inclusion in routine monitoring and health risk assessments in rapidly urbanizing regions.