Researchers recently became aware that bottlenose dolphins in the English Channel – the body of water that separates Southern England from northern France – are carrying a toxic concoction of chemicals in their flesh. A number of these chemicals have been barred for several decades, yet they continue to threaten the health of marine mammals.
Scientists found a mass build-up of industrial substances and mercury in the fatty tissue and skin of dolphins near the north-west coast of France. The French and Belgian scientists who made the discovery said that they detected amounts of pollutants much like those encountered in dolphins from the Mediterranean sea, the coast of the Guianas, the Everglades in Florida, and Guanabara Bay in Brazil.
If these chemicals were banned decades ago, how are they still present today?
A lot of the chemicals that were found, such as PCBs (polychlorinated biphenyls), have been prohibited as of the 1970s and 1980s, yet they still remain in the delicate ecosystem, where they can be passed through the food chain. The chemicals are capable of dissolving in oils, so they can gather in the marine mammals’ blubber. They can also be passed on through lactation during pregnancy.
“We suspect that elevated concentrations of PCBs can alter the reproduction of marine mammals, leading to a decrease of the number of newborns, affecting the renewal of the population,” stated Professor Krishna Das from the University of Liège, in Belgium, and co-author of the study.
PCBs, which used to be commonly found in lubricants and hydraulic fluids, can interfere with hormone receptors and the immune system, says Das.
An ornithologist at the University of Oldenburg, in Germany, Frank Mattig, says that this discovery supports what scientists have found in other species of marine life. According to Mattig, prime predators like dolphins and whales are especially susceptible to collecting toxins in their flesh.
The amount of chemicals that would be considered dangerous is unknown, however, other research has indicated that they are a health risk in high concentrations. “There’s good reason why they’re banned,” says Mattig.
The researchers say that there’s a clear need for better disposal of stocks and equipment, as well as better management of landfill leakage and dredging from rivers containing PCBs.