"Are Microplastics in Seafood a Cancer Risk?
“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 a plastic particle 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 a 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 on to 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 eats 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 ingested 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 products.
Though ideally all countries would do it together,
since plastic debris 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.