Legacy contaminants and low occurrence of PAHs in Sotalia guianensis from a highly impacted coastal region, Santos Basin, Brazil

Abstract Guiana dolphins ( Sotalia guianensis ) are coastal top predators exposed to persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs). We evaluated PCBs, DDTs, and PAHs in liver tissues of 70 stranded individuals from the Santos Basin, southeastern Brazil. The maximum concentrations reached, in wet weight, 759 ng g⁻ 1 for total PCBs and 242 ng g⁻ 1 for total DDTs. Parent PAHs were quantified in 20 samples, predominantly as naphthalene, with concentrations up to 200 ng g⁻ 1 . This indicates a low hepatic occurrence of the measured parent PAHs but does not necessarily imply low environmental exposure. Descriptively, PCB and DDT concentrations tended to be higher in individuals stranded in Rio de Janeiro and São Paulo than in Paraná and Santa Catarina, although interpretation is limited by the unbalanced sampling design and unknown movement histories. Fetuses generally showed lower PCB concentrations, while calves, juveniles, and adults exhibited substantial variability and overlapping concentration ranges, a pattern consistent with possible age-related accumulation but potentially influenced by other biological and geographic factors. Detection in fetal liver demonstrated prenatal exposure but did not allow maternal transfer to be quantified. Concentrations varied substantially among years between 2017 and 2022, but no consistent temporal trend was evident; annual sample sizes were small and uneven. Despite these limitations, this dataset provides an important regional baseline for future assessments of contaminant exposure in Sotalia guianensis.