We have long heard that some fish contain mercury and eating too much of them would harm our body. Besides mercury, what else could fish ingest and digest into their tissue? Recent study published in Nature, Scientific Reports says that 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."
In the study, Rochman and her co-authors fed medaka, a fish species often used in experiments, 3 different diets:
(1) regular fish food
(2) diet contains 10% "clean" plastic (with no pollutants)
(3) diet contains 10% plastic that had been soaking in the San Diego Bay for several months
When they tested the fish 2 months later, they found that the ones on the marine plastic diet (group #3) had much higher levels of persistent organic pollutants. Also, fish on the marine plastic diet were more likely to have tumors and liver problems.
When plastics are soaked in the ocean they behave just like a sponge which absorbs chemicals in the seawater. When the plastics got into the fish stomach they will interact with the stomach acid and release the chemicals absorbed, then get transferred into the bloodstream and tissue. Eating too much of such contaminated fish poses health risk.
According to Edward Humes, author of Garbology, there are 5 massive gyres of trash particles swirling around in the Indian, Atlantic and Pacific oceans alone. Those gyres contain plastic that has been weathered and broken down by the elements into these little bits, and it's getting into the food chain.
Even so, the consensus in the public health community still seems to be that the benefits of eating fish exceed the potential risks. Many researchers believe that the levels of dioxins, PCBs and other toxic chemicals in fish are generally too low to be of concern.
More studies are needed to really understand the impact of contaminated plastics in the ocean and risk poses to fish and human. 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.