Assessment of priority polycyclic aromatic hydrocarbons exposure to urban birds of Ahmedabad, India: Accumulation patterns, toxicological implications, source, and HPLC method validation

Polycyclic aromatic hydrocarbons (PAHs) are recognized as environmental threats because of their carcinogenic and mutagenic nature, widespread distribution, and potential for bioaccumulation in both aquatic and terrestrial ecosystems. Despite their relevance, limited data exist on PAH contamination in terrestrial birds, particularly in urban environments of developing countries like India. This study aimed to optimize and validate a high-performance liquid chromatography (HPLC) method for quantifying 15 priority PAHs listed by the US EPA and apply it to assess PAH residues in the tissues of six bird species from Ahmedabad, a densely populated and industrialized city in western India. The method demonstrated high precision, recovery, and sensitivity with LOQ ranged from 0.30 to 1.0 ng/g. Tissues (liver, kidney, muscle) from 37 individual birds representing six species were analysed. All birds studied had at least one PAH; however, the six-ring compounds indeno[1,2,3-cd]pyrene and benzo[g,h,i]perylene were not detected in any sample. Naphthalene (100%), phenanthrene (93%), and fluoranthene (46%) were the most frequently detected PAHs. Overall, distribution pattern indicates a dominance of low molecular weight PAHs in bird tissues. Source diagnostic ratios (PHE/ANT = 3.46; FLA/PYR = 6.46; FLA/(FLA + PYR) = 0.86) tentatively suggested a predominance of pyrogenic inputs associated with urban combustion sources; however, further studies are required to confirm source attribution, as these ratios were originally developed for abiotic matrices. Among the species examined, the Blue Rock Pigeon Columba livia showed among the higher total PAH burdens and, given its abundance in urban environments, close association with human activity, and ease of sampling, may serve as a practical bioindicator for PAH contamination. While the concentrations observed were below known toxicity thresholds, their consistent presence in multiple species suggests chronic exposure. These findings highlight the need for continued biomonitoring and targeted environmental management strategies to assess and mitigate long-term ecological risks associated with PAHs in urban Indian landscapes.