Seasonal variability and source diagnostics of ambient PAHs in Agra, India, using the CBPF and their health risk...

This study addresses the critical issue of polycyclic aromatic hydrocarbons (PAHs) bound to total suspended particulate (TSP) in urban-industrial environments, focusing on an understudied residential area in Agra, India-a city within the heavily polluted Indo-Gangetic Plain (IGP). The research aimed to investigate seasonal variations in PAH concentrations, identify their emission sources, and assess the associated health risks. TSP samples were collected during cold weather months (CWM; January and February 2023) and hot weather months (HWM; March-May 2023) and analysed for 16 priority PAHs. The results showed notably higher TSP (349.4 ± 56.2 µg m^-3) and PAH (1857.3 ng m^-3) levels in CWM compared to HWM (266.5 ± 33.1 µg m^-3 and 721.7 ng m^-3), with high-molecular-weight PAHs dominating in CWM and 3-ring PAHs prevailing in HWM. Source apportionment using diagnostic ratios and Positive Matrix Factorization (PMF) indicated vehicular emissions, fossil fuel combustion, and industrial activities as primary contributors. Conditional Bivariate Probability Function (CBPF) analysis revealed seasonal shifts in dominant source regions-southwest in HWM and northeast in CWM-correlating with local wind patterns. Health risk assessments based on benzo(a)pyrene toxicity equivalent (BaPeq-TEQ), benzo(a)pyrene mutagenic equivalent (BaPeq-MEQ), and Incremental Lifetime Cancer Risk (ILCR) highlighted carcinogenic and mutagenic risks from BaP, BbF, and DbA via dermal and ingestion pathways. These findings underscore the need for season-specific air pollution mitigation strategies, cleaner fuels, and stricter emissions controls. The study contributes to environmental chemistry by enhancing the understanding of TSP-bound PAH behaviour, exposure pathways, and health risks in urban residential zones, thereby supporting evidence-based policymaking aligned with Sustainable Development Goals 3 and 11.