Significant decrease in common dab (Limanda limanda) hepatic neoplasms revealed by long-term environmental monitoring

The prevalence of hepatic neoplasms (carcinogenesis) in the common dab (Limanda limanda) flatfish was investigated using data collected between 2004 and 2020 from five biogeographic UK marine regions including the Northern North Sea, Southern North Sea, Irish Sea, Eastern Channel, and Western Channel and Celtic Sea. Our assessment considered age-related confounding effects, providing an improved estimation of how hepatic neoplasm prevalence differs between regions and over time. The data indicated a significant decline in prevalence in both the Irish Sea and Southern North Sea regions, with a similar decreasing trend observed when all marine regions were analysed collectively. However, a higher prevalence was noted in dab from the Irish Sea compared to other regions, indicating additional environmental pressures. We explored potential correlations between hepatic neoplasms and concentrations of hazardous substances in biota and sediment including polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and metals. Concentrations of PCBs in biota were positively associated with hepatic neoplasm prevalence overall, although was primarily influenced by the Irish Sea region containing a disproportionately higher number of fishing locations compared to other regions. Cadmium, iron, manganese, and lead concentrations in sediments had a statistically significant effect on neoplasm prevalence, although this was believed to be correlation, not causation. The results are discussed within the context of monitoring the biological effects of contaminants and the associated challenges of long-term monitoring strategies.