Single-site source apportionment modeling of PM2.5-bound PAHs in the Tehran metropolitan area, Iran: Implications for source-specific multi-pathway cancer risk assessment

This study was designed to assess the occurrence, relationships, sources, spatiotemporal variations, and source-specific multi-pathway cancer risk of PM 2.5 -bound PAHs at three urban environments in Tehran, Iran during a one-year campaign (2018–2019). The mean concentrations of PM 2.5 -bound ∑16PAHs were 24.6, 26.7, and 38.9 ng m −3 in HFT, AZD, and SHR sites, respectively. High molecular weight (HMW) PAHs were the main PAHs in the fine particle phase (76–83.4%) compare to low molecular weight (LMW) PAHs (16.6–24%). Redundancy analysis (RDA) showed that relative humidity (RH) and temperature (T) along with O 3 , NO 2 , and PM 2.5 were critical driving factors affecting PAHs concentrations. Positive matrix factorization (PMF) extracted five PAHs emission sources: heavy-duty vehicles, light-duty vehicles, petrogenic, natural gas and coal/biomass combustion, industrial emissions, with different source contributions for each sampling site. The principal component analysis-multilinear regressions (PCA-MLR) and diagnostic ratios (DRs) methods indicated that the pyrogenic sources were the major sources of PM 2.5 -bound PAHs. The coefficient of divergence (COD) and Pearson correlation coefficient (R) of PAHs compounds and PMF derived source contributions (ng m −3 ) at paired sites indicated a relatively divergent spatiotemporal distribution. Based on incremental lifetime cancer risk (ILCR) levels of ∑PAHs source contributions, adults showed a more significant risk (1.33E-2.28E-05) than children (5.40E-9.22E-06). Source-specific-ILCR indicated that heavy-duty vehicles and natural gas-coal/biomass combustion emissions had the highest cancer risk contributions than the other apportioned sources. • PAHs were analyzed in PM 2.5 samples at three urban sites in Tehran, Iran for 1 year. • HMW PAHs indicated the main PAHs in PM 2.5 (76%–83.4%) compare to LMW PAHs. • PMF extracted 5 PAHs emission sources at each sampling site. • A significant potential cancer risk was observed for the adult group. • Heavy-duty vehicles, natural gas and coal/biomass combustion showed the higher cancer risk.