Killer whales (Orcinus orca) are considered to be one of the most contaminated cetacean species in the world. Being apex predators and capable of long-range migrations across oceans, these mammals consume prey from many locations in the world. Since toxins are often accumulated up the food chain, killer whale tissues may be a resting place for toxins that have entered the marine environment, and its organisms, from human activities.
The authors of a new research study, published in the journal Environmental Science & Technology, state that the potential health implications of selected ‘contaminants of emerging concern’ (CECs) and new persistent organic pollutants (POPs) in endangered Southern Resident and threatened Bigg’s (Transient) killer whales in the Northeastern Pacific (NEP) have not yet been documented. They set out to analyze samples of muscle and liver tissue from six individuals of each of these populations that were been stranded on the coast of British Colombia, Canada, between 2006 and 2018.
The researchers discovered that the whale tissue contained an array of chemical pollutants. The most prevalent were the CEC’s known as alkylphenols and polyfluoroalkyl substances (PFAS).
Just under half of the total pollutant load identified was derived from a substance called 4-nonylphenol or 4NP. This compound is used in the processing of pulp and paper, as well as in the production of soap, detergents and textiles. It can leak into the ocean via sewage treatment plants and industrial runoffs, where it is ingested by smaller organisms and moves up the food chain to reach top predators such as killer whales. The substance is listed as toxic in Canada, and can interact with the nervous system and influence cognitive function.
“This research is a wake-up call. Southern residents are an endangered population [of killer whales] and it could be that contaminants are contributing to their population decline. We can’t wait to protect this species,” said co-author Dr. Juan José Alava, principal investigator of the ocean pollution research unit at the Institute for the Oceans and Fisheries (IOF).
4NP is a CEC, which means it is a pollutant found in the environment that has, as yet, not been well studied. Because its effects are not yet understood, its use is not strictly regulated or monitored. “Very little is known of both the prevalence and health implications of 4NP as it has been studied in few marine mammals. This study is the first to find 4NP in killer whales,” said first author Kiah Lee, who undertook the research as an undergraduate at the University of British Colombia.
“This investigation is another example of an approach that takes into account the health of people, animals and the environment, using killer whales as a case study to better understand the potential impacts of these and other compounds on animal and ecosystem health,” said study co-author Dr. Stephen Raverty, IOF adjunct professor and veterinary pathologist with the B.C. Ministry of Agriculture and Food.
The remaining 54 percent of pollutants identified in the killer whale tissues belong to a group of compounds known as ‘forever chemicals’ because they persist in the environment. They are widely used in food-packaging materials, stain and water-repellent fabrics, cookware, and fire extinguishers. Many are listed as new persistent organic pollutants (POPs). These substances are toxic and are released into the environment through human activities, thus adversely affecting the health of humans and animals. Many of them are banned in Canada.
The most common pollutant from this group, present in the whale tissue, was 7:3-fluorotelomer carboxylic acid, or 7:3 FTCA. There are currently no restrictions on the production or use of 7:3 FTCA, but one of its potential parent chemicals is on a list of toxic substances proposed to be recognized as a new POP by the European Chemical Agency, under an international agreement, the Stockholm Convention, on POPs.
“This compound has not been found in B.C. before and it was found in killer whales, which are top predators. That means the contaminants are making their way through the food system,” said Dr. Alava.
In a further aspect of the current research, the scientists analyzed the pollutant content of tissues in a fetus found in one of the dead southern resident females. They found that all the pollutants present in the mother’s tissues were also present in the fetus, implying that all of these compounds are transferred across the placenta. Maternal transfer ratios indicated that 4NP was the most easily transferred contaminant, with a maternal transfer rate as high as 95.1 percent.
The study authors said that although too few killer whales have been screened for CECs and new POPs to infer the magnitude of contamination impact, these results raise concerns regarding pathological implications and potential impacts on fetal development and production of a viable neonate.
The experts encourage governments to help protect the endangered southern resident killer whales, and other marine life, by halting production of the chemicals of concern, including 4NP, and emerging POPs like 7:3 FTCA, as well as identifying and addressing potential sources of marine pollution in B.C. and Canada.
It’s not just the killer whales that are affected, said Dr. Alava. “We are mammals, we eat Pacific salmon as well, so we need to think about how this could affect our health as well as other seafood that we consume.”
By Alison Bosman, Earth.com Staff Writer
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