Are Microplastics in Seafood a Cancer Risk?

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

“Plastic debris in the [sea] is more than just an unsightly problem.” The concern is not so much discarded bobbing bottles, as tiny microplastic particles, raising questions about cancer. Wait; what does plastic have to do with cancer? Back in the 1950s, researchers had observed that when they wrapped the kidneys of rats with cellophane—to cause high blood pressure—they ended up inadvertently causing cancer. Cancers had started growing around the cellophane. So, they tried slipping all sorts of different plastics under the skin of rodents, and they all could produce malignant tumors. And then, if you feed rats some plastic microbeads, up to 6 percent of the particles end up in their bloodstream within 15 minutes.

So, could all this microplastics pollution be one of the reasons we’re seeing an increased number of tumors found in wildlife? Perhaps the global increase in wildlife cancers should be a “wake-up call.”

Now, we don’t know if it’s the plastic itself, or some of the chemical additives, like BPA, that are to blame. Maybe just having plastic particles stuck in your body causes some sort of mechanical irritation, beyond the chemical impact of the plastics as carriers of possible carcinogens. Some plastics may be cancer-causing in and of themselves, but all plastics “readily accumulate…harmful chemicals,” such as persistent pesticides like DDT, PCBs, flame-retardant chemicals, “increasing their concentration by orders of magnitude. This process is [then] reversible, with microplastics releasing contaminants upon ingestion.”

So, plastic debris may “act as a vector, transferring [persistent, bioaccumulative, and toxic substances] from the water to the food.” “Plastics are known to concentrate pollution from [water] by factors of up to 1 million times”—for example, for PCBs. In fact, that’s one of the ways environmental scientists sample for contamination levels: they use plastic to sponge up pollutants.

The concern, then, is that the plastic takes up all these toxins, and then goes and deposits them into the aquatic food chain, where they can “climb [up] the food chain. [and] ultimately into humans.” But this was all just theoretical…until now. “Chemical pollutants [glommed onto] ingested microbeads from personal care products [do indeed] accumulate in fish.” The longer you feed polluted microbeads to fish, the higher the levels of fish-flesh contamination. So, you can see how pollutant levels can then concentrate up the food chain, with maximum exposure in the apex predators, like killer whales or people. The herring can eat a bunch of brine shrimp, cod eat a bunch of herring, then halibut or tuna eat a bunch of cod, and then we can scoop it all up in the end.

So, we know “[i]ngested plastic [can] transfer…hazardous chemicals to fish,” which then accumulate, and can cause liver toxicity and pathology in the fish. But, what about in people? Well, we know that in the US, of all food categories, fish has “the highest levels of PCBs, dioxins,” and other pollutants. But, we don’t really eat a lot of fish in this country. So, is it really a problem?

Well, it’s hard to come up with a “tolerable daily intake” of these kinds of chemicals. But, the World Health Organization recommends staying under like one to four units a day (measured in picograms of toxic equivalents). The European Union came up with a smaller number, like no more than two a day on average, and in the U.S. we’re already past that. So, “there is some concern for toxicity from PCBs,” given the current levels of PCBs and plastic debris polluting the ocean. “There is no “room” for additional PCB body burden.” So, what can we do about it?

Well, we can practice the three R’s: reduce, reuse, and recycle plastic items, for example, shopping with reusable tote bags. On a policy level, we could ban the use of plastic microbeads in cosmetics and personal care product—though ideally, all countries would do it together, since plastic “[d]ebris dropped anywhere on earth may end up being transported…to the ocean where it” can travel around the world. So: “Whatever strategies are adopted, international cooperation will be critical in limiting the risk to the oceans and the risk to humans from eating seafood.”

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Image credit: The NOAA Photo Library. Image has been modified.

Motion graphics by Avocado Video

• animal studies
• BPA
• cancer
• dioxins
• endocrine disruptors
• environment
• fish
• hormones
• industrial pollutants
• PCBs
• persistent organic pollutants
• plastic
• seafood
• tuna
• World Health Organization