Chemical pollution could wipe out half of the killer whale populations

(CNN) – Chemical pollutants banned more than 40 years ago still have a devastating effect on marine life and could kill half of the world's population of killer whales by the end of the century.

According to a new study published in the journal Science, it revealed that polychlorinated biphenyls (PCBs) were the most exposed to killer whales, or orcas, which were once widely used as coolants and in the production of carbonless carbonless paper. have been found to be highly toxic and carcinogenic.

PCB production was banned in the United States in 1979 and as part of an international treaty in 2001, but they are still used in many parts of the world and should not be completely phased out until 2025.

This has led to PCB infiltration into the oceans, where they pose a particular risk to marine mammals at the top of the food chain, such as orcas. Because chemicals do not break down easily, their concentration increases in the body of predators as they eat more and more fish contaminated with PCBs.

For mammals, PCB contamination is intergenerational, with mothers transmitting chemicals to their offspring through milk.

Orcas are the last link in a long food chain and are therefore among the most affected by this problem in their 50 to 80 year old lives.

Researchers have found that PCB levels reaching 1,300 milligrams per kilogram in the fat of some orcas, studies show that only 50 milligrams per kilogram can cause infertility and immune system problems.

"Absolutely tragic"

The researchers found that the effects of PCBs on fertility and immunity had devastated many populations, resulting in a rapid decline in the number of killer whales in 10 of the 19 populations studied.

"The results are surprising. We find that more than half of the killer whale populations studied around the world are seriously affected by PCBs, "said Jean-Pierre Desforges of the University of Aarhus in Denmark in a statement.

The situation is worse in Brazil, in the Strait of Gibraltar, in the north-east Pacific and around the British Isles, where the Ailsa Hall mammal research unit in Scotland said "we rarely see newborn killer whales ".

Desforges added that it was "scary to see that models predict a high risk of population collapse in these areas by 30 to 40 years".

Due to the long life of whales, the high levels of PCBs released into the environment decades ago still have an effect that will only increase as deadly pollutants continue to grow. be produced and used.

Under the Stockholm Convention, to which 152 countries around the world are signatories, all PCB use should be phased out by 2025 and efforts are under way to treat existing wastes in an environmentally sound manner.

But co-author of the study, Paul Jepson of the UK's Institute of Zoology, said the new study showed that current efforts "have not been effective enough to prevent PCB build up in the UK. … living species as long as the killer whale "

"There is therefore an urgent need for additional initiatives compared to those of the Stockholm Convention," said Jepson in a statement.

ORCA, a UK charity that studies and protects whales and other marine mammals in Europe, described the results as an "absolutely tragic state that requires immediate action".