We've long known that the fish we eat are exposed to toxic chemicals in the rivers, bays and oceans they inhabit. The substance that's gotten the most attention — because it has shown up at disturbingly high levels in some fish — is mercury.
But mercury is just one of a slew of synthetic and organic pollutants that fish can ingest and absorb into their tissue. Sometimes it's because we're dumping chemicals right into the ocean. But as a study published recently in Nature, Scientific Reports helps illuminate, sometimes fish get chemicals from the plastic debris they ingest.
"The ocean is basically a toilet bowl for all of our chemical pollutants and waste in general," says Chelsea Rochman, a postdoctoral researcher at the University of California, Davis, who authored the study. "Eventually, we start to see those contaminants high up in the food chain, in seafood and wildlife."
For many years, scientists have known that chemicals will move up the food chain as predators absorb the chemicals consumed by their prey. That's why the biggest, fattiest fish, like tuna and swordfish, tend to have the highest levels of mercury, polychlorinated biphenyls (PCBs) and other dioxins. (And that's concerning, given that canned tuna was the second most popular fish consumed in the U.S. in 2012, according to the National Fisheries Institute.)
What scientists didn't know was exactly what role plastics played in transferring these chemicals into the food chain. To find out, Rochman and her co-authors fed medaka, a fish species often used in experiments, three different diets.
One group of medaka got regular fish food, one group got a diet that was 10 percent "clean" plastic (with no pollutants) and a third group got a diet with 10 percent plastic that had been soaking in the San Diego Bay for several months. When they tested the fish two months later, they found that the ones on the marine plastic diet had much higher levels of persistent organic pollutants.
"Plastics — when they end up in the ocean — are a sponge for chemicals already out there," says Rochman. "We found that when the plastic interacts with the juices in the [fish's] stomach, the chemicals come off of plastic and are transferred into the bloodstream or tissue." The fish on the marine plastic diet were also more likely to have tumors and liver problems.
While it's impossible to know whether any given fish you buy at the seafood counter has consumed this much plastic, Rochman's findings do have implications for human health, she notes. "A lot of people are eating seafood all the time, and fish are eating plastic all the time, so I think that's a problem."
And there's a lot of plastic out there in the open ocean. As Edward Humes, author of Garbology, told Fresh Air's Terry Gross in 2012, the weight of plastic finding its way into the sea each year is estimated to be equivalent to the weight of 40 aircraft carriers.
Consider the five massive gyres of trash particles swirling around in the Indian, Atlantic and Pacific oceans alone. Those gyres, Hume told Gross, contain "plastic that has been weathered and broken down by the elements into these little bits, and it's getting into the food chain."
One of those gyres is the infamous Great Pacific Garbage Patch. Fish could encounter the plastic in those gyres, but also much closer to shore, says Rochman.
Even so, the consensus in the public health community still seems to be that the benefits of eating fish — because of their omega-3 fatty acids, among other assets — exceed the potential risks. And many researchers advocating for Americans to increase their fish consumption argue that the levels of dioxins, PCBs and other toxic chemicals in fish are generally too low to be of concern.
The Environmental Protection Agency does put out advisories to warn consumers when fish get contaminated with chemicals in local U.S. waters. But a lot of our seafood now comes from foreign waters, which the EPA does not monitor. Just a tiny fraction of imported fish get tested for contaminants.
As for Rochman, she says her research in marine toxicology has persuaded her to eat seafood no more than twice per week. And she now avoids swordfish altogether.
First of all: WOW. We did our live show at NPR HQ this week, and it was wonderful, and all of you who attended made a fantastic audience. You'll be hearing the live show in two segments over the holidays while we take a rest, but in the meantime, we've got a brand-new show to roll out.
Our first topic is the Disney film Frozen, which raises some of the same princess questions as Wreck-It Ralph, but in different ways. Glen has an unusual spin, let's say, on the movie's best-received song, and the guys in general find themselves a bit underwhelmed by the story. I, on the other hand, tell them they are emphatically wrong. Trey also makes a sloth reference that you should know if you don't already.
We also take the occasion of the death(ish) of a character on Family Guy to talk about character deaths, whether they arise from unexpected off-screen events or a decision to change direction. Now, BE WARNED, there are some old shows — including Buffy and Star Trek: TNG and MASH — where we discuss significant character deaths, because it's the only way to do the segment. But we stayed away from new stuff.
As always, we close the show with what's making us happy this week. Stephen cites his kids' wish lists (totally pop culture!) before citing a recent Deadspin piece you should definitely read as long as you enjoy swears. Trey mentions the comedy stylings of a favorite actress, and he also has a lot to say about squirrel trivia. Glen very much enjoyed a movie that didn't sound like it was made for him. I very much enjoyed a trailer that came before Frozen, and I also shouted out our new merch, which isn't online yet but is available for sale in the shop in the lobby at NPR HQ — which now includes glasses and shakers in addition to the awesomely soft shirts.
We communicate with each other in all sorts of ways, spoken and unspoken. In this hour, TED speakers reflect on how our words and methods of communication affect us, more than you might expect.
Part 4 of the TED Radio Hour episode Spoken And Unspoken.
About Mark Forsyth's TEDTalk
Etymologist Mark Forsyth shares the surprising back story on the term "president."
About Mark Forsyth
Mark Forsyth is an author, blogger, journalist, proofreader and ghostwriter. On his blog, the Inky Fool, he dispells grammar myths. His book The Etymologicon takes "a circular stroll through the hidden connections of the English language" by history of one word or phrase with each chapter.
Part 5 of the TED Radio Hour episode Spoken And Unspoken.
About Amy Cuddy's TEDTalk
Body language affects how others see us, but it may also change how we see ourselves. Social psychologist Amy Cuddy shows how "power posing" can affect our brains, and might even have an impact on our chances for success.
About Amy Cuddy
Amy Cuddy is a professor and researcher at Harvard Business School, where she studies how nonverbal behavior and snap judgments affect people. Her research reveals we can change other people's perceptions — and even our own body chemistry — simply by changing body positions.