Study shows microplastics can migrate to whale and dolphin tissue

A short-finned pilot whale and its calf surface off the coast of Manteo, NC. These are among the species found with microplastics in their tissues.(Greg Merrill Jr./NMFS Permit #22156)

New research indicates that microplastics don’t just get ingested into marine mammal’s digestive tracts, but can migrate into their tissue.

“This is an extra burden on top of everything else they face: climate change, pollution, noise, and now they’re not only ingesting plastic and contending with the big pieces in their stomachs, they’re also being internalized,” Greg Merrill Jr., the study’s lead author and a fifth-year graduate student at the Duke University Marine Lab, said in a statement.

“Some proportion of their mass is now plastic.”

To do the study, researchers looked at tissue samples from 32 individual marine mammals.

Species looked at in study

Dolphins: Bottlenose Dolphin

Seals: Bearded Seal; Spotted Seal; Ringed Seal

Whales: Minke Whale; Fin Whale; Humpback Whale; Gray Whale; Pilot Whale; Pygmy Sperm Whale; Beluga Whale

The samples were gathered from whales in Alaska, California and North Carolina which had either been stranded or had been harvested by subsistence hunters.

Plastics found in four areas of body 

Knowing that plastics are attracted to fats, the researchers sampled fat from three places on the animals: the blubber; the melon, or fat, on toothed whales foreheads; and on the fat located on whale’s lower jaws.

The researchers also sampled the animals lungs.

In the end, the found microplastics in all four areas.

Graphical Abstract from a paper in Environmental Pollution showing where in a whale’s anatomy plastic particles may be found. Plastics are lipophilic and may home in on the blubber and fat pads. (Greg Merrill Jr./Duke University)

“While microplastics have been previously documented in marine mammal gastrointestinal tracts, this is the first study to identify translocation and deposition of microplastics into various marine mammal tissues,” the paper said. 

“Whether the concentration of microplastic in the tissues examined here present a health threat to marine mammals remains to be examined, however the presence of microplastics embedded in internal organs underscores the ubiquity of the pervasive plastic pollution problem afflicting the oceans and its inhabitants with rippling implications for humans.”

Effects on health to be looked at

The plastic particles found measured from 198 microns to 537 microns, compared to a human hair which is about 100 microns in diameter, the researchers said. 

The most common colour of plastic found in all four tissue areas was blue plastic.

Most common plastics found in the marine mammals
  • Polyester fibers, a byproduct of laundry machines
  • Polyethylene,  a component of beverage containers

Merrill said the next research steps include determining the health effects of the plastics on the animals. 

“Now that we know plastic is in these tissues, we’re looking at what the metabolic impact might be,” Merrill said. 

‘Underscores scale of this problem’

Looking at the downstream effects on humans after consuming marine mammals is also an important area of further inquiry, the paper said.

“Identifying the mechanism by which these particles enter the circulatory system (as many here were larger than can be explained by transcellular uptake or paracellular diffusion) can help inform our understanding of microplastic particle retention time in the body: are these particles permanently deposited or are they transitory?,” the researchers said.

“Ultimately, the development of a biomarker that can be used to evaluate microplastic contaminant loads in living individual animals, perhaps via biopsy or fecal sample, would allow for the assessment of risk to wild populations, native subsistence users, and marine mammal consumers globally.”

A blue microplastic fiber turned up on this glass fiber filter from the lung tissue of a beluga whale. (Greg Merrill Jr./Duke University Marine Lab)

Ultimately, Merrill said the findings drive home the pervasiveness of plastic in the environment. 

“We haven’t done the math, but most of the microplastics probably do pass through the gut and get defecated,” he said. “But some proportion of it is ending up in the animals’ tissues.

“For me, this just underscores the ubiquity of ocean plastics and the scale of this problem. Some of these samples date back to 2001. Like, this has been happening for at least 20 years.”

Write to Eilís Quinn at eilis.quinn(at)

Related stories from around the North:

Canada: Cotton fibres, microplastics pervade Eastern Arctic, study finds, The Canadian Press

Finland: Citizens’ initiative prompts Finnish lawmakers to consider microplastics ban, Yle News

Norway: Report reveals high levels of microplastics on Norway’s Arctic coast, The Independent Barents Observer

Eilís Quinn, Eye on the Arctic

Eilís Quinn is an award-winning journalist and manages Radio Canada International’s Eye on the Arctic news cooperation project. Eilís has reported from the Arctic regions of all eight circumpolar countries and has produced numerous documentary and multimedia series about climate change and the issues facing Indigenous peoples in the North.

Her investigative report "Death in the Arctic: A community grieves, a father fights for change," about the murder of Robert Adams, a 19-year-old Inuk man from Arctic Quebec, received the silver medal for “Best Investigative Article or Series” at the 2019 Canadian Online Publishing Awards. The project also received an honourable mention for excellence in reporting on trauma at the 2019 Dart Awards in New York City.

Her report “The Arctic Railway: Building a future or destroying a culture?” on the impact a multi-billion euro infrastructure project would have on Indigenous communities in Arctic Europe was a finalist at the 2019 Canadian Association of Journalists award in the online investigative category.

Her multimedia project on the health challenges in the Canadian Arctic, "Bridging the Divide," was a finalist at the 2012 Webby Awards.

Her work on climate change in the Arctic has also been featured on the TV science program Découverte, as well as Le Téléjournal, the French-Language CBC’s flagship news cast.

Eilís has worked for media organizations in Canada and the United States and as a TV host for the Discovery/BBC Worldwide series "Best in China."

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