Biliary OH-PAH Profiles for Distinguishing Petrogenic and Pyrolytic Sources in Oil-Affected Tropical Estuaries

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants of concern due to their persistence, bioaccumulation potential, and toxic effects on aquatic organisms. In fish, PAHs are rapidly metabolized, making biliary hydroxylated PAH metabolites (OH-PAHs) useful biomarkers of recent exposure and biological availability. In oil-affected coastal areas, these metabolites may provide valuable information for assessing biological exposure to PAHs and supporting post-spill environmental monitoring. This study evaluated the spatial variability of six biliary OH-PAHs in estuarine catfish (Cathorops spixii and Sciades spp.) collected from eight tropical estuaries along the northeastern Brazilian coast historically affected by the 2019 Brazilian oil spill and subjected to different degrees of anthropogenic pressure. Bile samples were analyzed by high-performance liquid chromatography with fluorescence detection (HPLC-F) for 1-hydroxynaphthalene (1-OHNaph), 2-hydroxynaphthalene (2-OHNaph), 2-hydroxyfluorene (2-OHFlu), 9-hydroxyphenanthrene (9-OHPhen), 1-hydroxypyrene (1-OHPyr), and 3-hydroxybenzo[a]pyrene (3-OHBaP). Biliary OH-PAHs showed marked spatial variability among estuaries. The Cocó estuary exhibited the highest concentrations of 1-OHNaph and 9-OHPhen, indicating comparatively elevated biological exposure to PAHs at this site, whereas lower concentrations were generally observed in less urbanized systems. Naphthalene- and phenanthrene-related metabolites predominated across the investigated estuaries, revealing distinct spatial patterns of exposure to lower-molecular-weight PAHs. No significant sex-related differences were observed in biliary OH-PAH concentrations, suggesting that spatial variability was more pronounced than sex-related differences in the observed exposure profiles. The contrasting metabolite profiles among estuaries highlight the influence of different local contaminant inputs and demonstrate the potential of biliary OH-PAH profiles for characterizing PAH exposure in coastal areas with a history of oil contamination and multiple anthropogenic pressures. Overall, the results demonstrate the potential of biliary OH-PAH profiles as a biomonitoring tool for assessing biological exposure and PAH bioavailability in oil-affected tropical estuaries. By providing organism-based evidence of contaminant exposure, this approach can complement conventional environmental chemistry and contribute to post-spill monitoring, environmental impact assessment, and the prioritization of areas for remediation and coastal management.