Analysis indicates ingested microplastics migrate into whales' fat and organs
Duke
University
Summary:
Microscopic
plastic particles have been found in the fats and lungs of two-thirds of the
marine mammals in a graduate student's study of ocean microplastics. The
presence of polymer particles and fibers in these animals suggests that
microplastics can travel out of the digestive tract and lodge in the tissues.
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. Credit: Greg Merrill Jr., Duke University
Microscopic
plastic particles have been found in the fats and lungs of two-thirds of the
marine mammals in a graduate student's study of ocean microplastics. The
presence of polymer particles and fibers in these animals suggests that
microplastics can travel out of the digestive tract and lodge in the tissues.
The study, slated
for the Oct. 15 edition of Environmental
Pollution, appeared online this week.
Harms that
embedded microplastics might cause to marine mammals are yet to be determined,
but plastics have been implicated by other studies as possible hormone mimics
and endocrine disruptors.
"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," said Greg
Merrill Jr., a fifth-year graduate student at the Duke University Marine Lab.
"Some proportion of their mass is now plastic."
The samples in
this study were acquired from 32 stranded or subsistence-harvested animals
between 2000 and 2021 in Alaska, California and North Carolina. Twelve species
are represented in the data, including one bearded seal, which also had plastic
in its tissues.
Plastics are
attracted to fats -- they're lipophilic -- and so believed to be easily
attracted to blubber, the sound-producing melon on a toothed whale's forehead,
and the fat pads along the lower jaw that focus sound to the whales' internal
ears. The study sampled those three kinds of fats plus the lungs and found
plastics in all four tissues.
Plastic particles
identified in tissues ranged on average from 198 microns to 537 microns -- a
human hair is about 100 microns in diameter. Merrill points out that, in
addition to whatever chemical threat the plastics pose, plastic pieces also can
tear and abrade tissues.
"Now
that we know plastic is in these tissues, we're looking at what the metabolic
impact might be," Merrill said. For the next stage of his dissertation
research, Merrill will use cell lines grown from biopsied whale tissue to run
toxicology tests of plastic particles.
Polyester fibers,
a common byproduct of laundry machines, were the most common in tissue samples,
as was polyethylene, which is a component of beverage containers. Blue plastic
was the most common color found in all four kinds of tissue.
A 2022 paper in
Nature Communications estimated, based on known concentrations of microplastics
off the Pacific Coast of California, that a filter-feeding blue whale might be
gulping down 95 pounds of plastic waste per day as it catches tiny creatures in
the water column. Whales and dolphins that prey on fish and other larger
organisms also might be acquiring accumulated plastic in the animals they eat,
Merrill said.
"We haven't
done the math, but most of the microplastics probably do pass through the gut
and get defecated. But some proportion of it is ending up in the animals'
tissues," Merrill said.
"For me, this
just underscores the ubiquity of ocean plastics and the scale of this
problem," Merrill said. "Some of these samples date back to 2001.
Like, this has been happening for at least 20 years."
This work was
supported by the National Science Foundation, the North Carolina Wildlife
Federation and North Carolina Sea Grant (2018-2791-17).
Story Source:
Materials provided by Duke University. Original written
by Karl Leif Bates. Note:
Content may be edited for style and length.