Orcas continue to carry toxic substances banned decades ago

Nov. 7 () –

Killer whales off Atlantic Canada maintain high levels of toxic chemicals banned decades ago, which They expose them to high risk of immunological and reproductive problems.

A study, published in Science of the Total Environmentwas based on information obtained from skin samples collected from live whales and dolphins near the French territory of Saint Pierre and Miquelon, south of Newfoundland, downstream of the Gulf of Saint Lawrence. The researchers analyzed biopsies from 50 animals, representing six species of cetaceans (whales or dolphins).

The researchers discovered that The outlook was more encouraging in the case of other whales and dolphins studied; Their pollution levels were mostly below thresholds for serious health risks.

Overall, researchers found that levels of harmful chemicals such as polychlorinated biphenyls (PCBs) and organochlorine pesticides (such as DDT) have decreased since the 1980s and 1990s. In the past, they were used in industrial and agricultural applications, but they were banned decades ago, although They persist in the environment due to their stable chemical structure.

The presence of these persistent organic pollutants (POPs) had a particularly negative impact on orcas due to their feeding habits, the researchers said. Killer whales and other toothed whales feed on species found higher up the food chain and/or in coastal environments.

The researchers found that these whales had higher levels of contaminants than baleen whales, which feed on lower prey such as small fish in schools and krill in the open ocean. This suggests that coastal areas continue to have higher levels of pollutants, probably due to historical and current sources of contamination.

“While it is encouraging to see an overall decrease in pollutant levels in baleen whales and small dolphins, demonstrating that regulations have had a positive impact, the situation for orcas is particularly worrying,” he said. in a statement Anaïs Remili, lead author of the study and former postdoctoral researcher in the Department of Natural Resource Sciences, who conducted the research while at McGill.

“The risk thresholds we use were established decades ago and we need to better understand how these contaminants affect the health of cetaceans today“.

Remili emphasized the need for continued research and monitoring to better understand the risks that contaminants pose to marine mammals.

“We need to investigate current sources of pollution, prevent the release of new contaminants, and evaluate the combined effects of multiple stressors on whale health,” he said.

The study recommends future research work to update toxicity thresholds, investigate how contaminants affect whales’ hormones and immune systems, and develop specific conservation strategies. Persistently high levels of pollutants in orcas highlight the need for a focused approach to reducing chemical pollution in the Northwest Atlanticthe researchers said.