Spatial and temporal variability of organochlorine compounds in raft mussel in Galician Rías from 2012 to 2022. Human risk assessment.

This study investigates the spatial and temporal variability of ten polychlorinated biphenyls (PCBs) and seven organochlorine pesticides (OCPs) in raft cultured mussels (Mytilus galloprovincialis) from five Galician Rías (NW Spain) over the period 2012-2022. A total of 336 mussel samples from 27 sampling sites were analyzed by GC-MS/MS. Spatial variability was assessed using multifactorial analysis of variance (ANOVA) and principal component analysis (PCA), while temporal variability was evaluated using trend analysis. PCBs showed the greatest spatial variability, with significantly higher concentrations in the industrialized Rías de Vigo and Ares-Betanzos and lower levels in Muros-Noia and Arousa. PCB profiles were dominated by highly chlorinated congeners, particularly PCB153 and PCB138, indicating the persistence of aged and historical contamination. OCP concentrations were generally low and did not show significant differences among Rías. DDT metabolites, mainly p,p'-DDE and p,p'-DDD, predominated over parent DDT, consistent with historical inputs and environmental degradation. Principal component analysis confirmed that PCBs were the main contributors to geographical differentiation, with the first three components explaining 75.5% of the total variance. Temporal analysis revealed generally stable or decreasing concentrations of most organochlorine compounds, although localized increases were observed at some sampling sites, highlighting spatial heterogeneity in contaminant dynamics. Human health risk assessment showed that all estimated risk quotients were below one, indicating no expected health risk from mussel consumption under the assessed conditions.