Study shows microplastics can migrate to whale and dolphin tissue

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.

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.

“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.

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.”

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)cbc.ca

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