New research has found that the levels of toxic industrial chemicals, which were banned over 40 years ago, are rising in otters in Wales.
The Cardiff University Otter Project, in collaboration with Natural Resources Wales analysed liver samples from Eurasian otters (Lutralutra) collected across Wales between 2010 and 2019. The team found Polychlorinated biphenyls (PCBs) in every otter they tested. Of the otters sampled, 16% exceeded a toxic threshold, which is known to impair reproduction.
PCBs were once widely used in electrical equipment, paints, and plastics due to their stability and heat resistance. Although banned in the 1980s, their environmental persistence means they continue to accumulate in wildlife, and can be found in high concentrations in top predators.
Dr Emily O'Rourke, lead author of the study from Cardiff University, said: "While PCB concentrations in water and fish are often too low to detect – and fall within current quality standards under the Water Framework Directive – our research adds to growing evidence that they are still accumulating to harmful levels in top predators through the food chain."
These results show that our current water quality standards may not fully protect wildlife at the top of the food web. Continued monitoring and stronger international action are urgently needed to manage legacy pollutants and protect the health of our rivers.
Earlier research by the Otter Project found PCB levels had declined between 1992 and 2009, but these new data show concentrations have been rising again since 2010. Higher concentrations were found in otters from coastal and low-lying areas, suggesting that PCBs stored in river and coastal sediments are being remobilised into the environment.
Dr O'Rourke added: "During their period of widespread use in the 1950s and 60s, PCBs accumulated in river and marine sediments, these sediments are now releasing the chemicals back into the environment. Climate change, through more frequent storm events, flooding, and erosion, is likely accelerating this process. Managing contaminated sediments and addressing the impacts of climate change are critical for protecting river ecosystems."
Dr Elizabeth Chadwick, Principal Investigator on the Otter Project, said: "Through the Otter Project's archive – holding samples from more than 4,500 otters found dead across Britain since 1992 – we can track long-term changes in pollution and identify emerging chemical threats before they cause lasting harm."
This new research underscores the importance of continued monitoring, and the need for better international efforts to manage these legacy pollutants.
The research, Increasing concentrations of polychlorinated biphenyls (PCBs) in Eurasian otters (Lutra lutra) from Wales suggest remobilisation from sediment sinks , was published in Environmental Pollution.
