Harbor Porpoise Calves Exposed to Toxic Chemicals in Mothers’ Milk

(CN) – Harbor porpoise mothers rid themselves of human-made neurotoxic chemicals found in the ocean by transferring the dangerous mixture to their calves, according to research released Monday.

A dead harbor porpoise. (Science of the Total Environment)

In a study released in the journal Science of the Total Environment, biologists examined the level of polychlorinated biphenyl, a group of toxic chemicals, in harbor porpoises around the United Kingdom. PCBs were commonly used in paints, surface coatings and electrical equipment in the 1980s until they were banned due to their toxic effects on the health of both humans and wildlife.

Some 200 variants of PCBs have been found in marine mammals, some more dangerous than others. What research scientists discovered, however, is the more persistent toxins stay with the mother until they transfer to infants when feeding. The toxic chemicals are particularly dangerous to the young during their brain development.

Lead author Rosie Williams, doctoral researcher at the Zoological Society of London and Brunel University London, called it a “tragic irony that juvenile porpoises are being exposed to a toxic cocktail of chemicals during feeding – when all they’re supposed to be getting are the vital nutrients they need for the crucial developmental stage of their life.”

Agriculture giant Monsanto produced PCBs in the U.K. until the late 1970s. The U.K. government banned closed uses of PCBs in new electrical equipment in 1981. Although production of PCBs has decreased dramatically, they are still widely used.

Williams said the study shows scientists need to rethink how they monitor the toxic chemicals, which still affect marine mammals.

“Previously, scientists tended to monitor PCB concentrations by grouping them together and treating them as one chemical, but as we know, they’re a group of chemicals with different toxicity levels so it was a bit like trying to measure how much caffeine someone’s had – without knowing whether they drank three cans of Red Bull or three cups of tea,” Williams said.

She added that PCBs represent a danger to other marine mammals already threatened by human activities.

“Studying PCB exposure in more abundant species like porpoises, helps us to predict their effects in more vulnerable species already low in numbers; such as our native population of orcas in the U.K. that are facing extinction because of PCBs, with only eight remaining,” she said. “As top predators, killer whales are exposed to some of the highest levels of PCBs, because there is an accumulative effect of PCBs as you go up the food chain.”

The research team examined the world’s largest dataset of cetacean toxicology, with samples collected from 696 harbor porpoises stranded in the U.K. between 1992 and 2015. Williams said improved monitoring of the toxic chemicals can help to stop the ongoing effects.

“It’s obvious that marine mammals are still experiencing the lingering impacts of PCBs, so identifying the sources and pathways they’re entering our oceans is a vital next step to preventing further pollution,” she said.

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