‘Almost 20 percent of sexually mature females showed evidence of stillbirth, foetal death or recent abortion …’
FRISCO — Even though PCBs were banned in the UK more than 30 years ago, researchers are still finding moderately “moderately high” levels of the toxic chemicals in the tissue of harbor porpoises.
The marine mammals around parts of the British Isles are struggling to successfully reproduce as a result of chemical pollutants found in European waters, according to new research led by the Zoological Society of London.
The findings, published in PLOS ONE, found that polychlorinated biphenyls, once used in industrial equipment, such as electrical components and certain paints, accumulates in the fat tissue of whales, dolphins and porpoises – known collectively as cetaceans – and can remain there throughout their lifetime.
In 2010, researchers with the National Oceanic and Atmospheric Administration reported that they found the highest levels of PCBs ever reported in marine mammals when they studied dolphins off the coast of Georgia in August 2009. The research was conducted by NOAA’s Center for Oceans and Human Health at the Hollings Marine Lab.
Another study from the same lab found persistent and widespread pollution buildup in bottlenose dolphins living along the the U.S. East and Gulf of Mexico coasts and Bermuda. Another team looked at concentrations of perfluorinated compounds in beluga whales in Alaskan waters.
Exposure to PCBs can weaken cetacean immune systems and reduce breeding success, and the study reported a large number of cases of reproductive failure: Almost 20 percent of sexually mature females showed evidence of stillbirth, foetal death or recent abortion. A further 16.5 percent had infections or tumours of reproductive organs that could have contributed to breeding failure. The study also found lower pregnancy rates in UK harbour porpoises compared to those living in much less PCB-polluted regions.
Harbour porpoise calves inherit PCB contamination from their mothers through suckling, continuing the problem for future generations.
“Reproductive failure could have occurred in almost 40 percent of mature females sampled in this study,” said Dr Sinéad Murphy who led the study during her Marie Curie Research Fellowship at ZSL.
“PCBs may have reduced foetal or newborn survival, something which has also been observed in other mammals. UK harbour porpoises are part of a larger north-east Atlantic population and our research suggests a population-level risk from PCB exposure.”
“PCBs were banned in 1981 in the UK, but PCB concentrations only stopped declining in the blubber of UK harbour porpoises around 1998. PCB levels in many UK porpoises are still high, which could mean continued negative effects on health and breeding,” said Dr Paul Jepson, co-author of the study at ZSL and lead veterinarian on the UK Cetacean Strandings Investigation Programme.