Authors' note: This article is sourced from counterpunch.org
When Chelsea Rochman at the University of Toronto and colleagues began their study on medakas (small Japanese rice paddy fish), they did not expect to find what they did.
They first soaked ground-up polyethylene in San Diego Bay for three months and then fed it to these fish along with a laboratory diet. They also fed the same diet to a comparison group of medakas but along with virgin polyethylene also ground-up. The medakas eating the plastic immersed in the Bay suffered greater liver damage. How much of a danger then is our seafood?
Defined as less than 5mm in size, microplastics have been found in 114 types of aquatic life, over half of which are consumed by humans. Oysters exposed to food-container plastic (polystyrene) have fewer eggs and impaired less-motile sperm. Does eating them do the same to us? Nobody knows. A comprehensive study of plastics in seafood and its implications for human health points to the gaps in our knowledge. It calls for more research into the toxicity of various plastics and in identifying lower-risk seafood.
There is some evidence for the quantity of microplastic pieces per cubic meter of water from the surface to a depth of 1000 meters in one study. The numbers range from four pieces at the surface increasing to about a dozen at 200 meters down then declining to three or so at a 1000 meters down. It is certainly not super dense. At the same time, little fish ingesting it and bigger fish eating smaller ones, and one can see a problem developing, particularly for us the final consumer.
The copious plastic debris flowing into the ocean estimated at 8 million tons annually continues to add to the 100 million tons already there. Engineering experts at Stanford University have discussed "the potential for meaningful change" in the status quo. They have some interesting observations: Microplastics are now in "about a quarter of the sea foods in our markets and even in table salt." They are also in "94 percent of tap-water samples in the US and in nearly every brand of bottled water." At this we checked tap water and some bottled water and did not notice any. Insidious, if these are microscopic.
Research in other parts of the world exemplify the global extent of the microplastics menace. In a study of commercial fish caught off the Portuguese coast, microplastics were found in 19.8 percent of the 26 species of fish tested. Plastic polymers, polyethylene and polypropylene as well as fibers like polyester, rayon and nylon had been ingested. As might be expected, the fish taken off Lisbon and its environs were worst affected.
In another study, fish and bivalves taken from markets in California and Makassar, Indonesia, were examined for anthropogenic debris. Plastic was again confirmed in seafood sold for human consumption. Debris was found in about a quarter of individual fish and a third of shellfish, raising concerns about human health.
North Sea fish have been studied for plastic ingestion also. Foekema and his fellow researchers found particles up to 4.8 mm in five of seven common North Sea fish species. Usually only one particle was found and in only 2.6 percent of the 1204 individual specimens tested. Cod showed the highest frequency with one-third involved. In another study of 400 individual fish from four species, only two particles were found, both in one individual, a sprat, confirming the relative low incidence of plastics in North Sea fish. The particles in the sprat were microbeads.
Then there is the ubiquitous cigarette butt. Is there something prophetic about dropping and stubbing it as the final act of a habit statistically known to shorten the lives of smokers? Discarding butts may be socially acceptable but when 6.5 trillion cigarettes are smoked each year around the world, and an estimated two-thirds of the ends flicked away carelessly, butts become the most littered plastic item. Made of cellulose acetate they degrade slowly, and then into tiny microplastic pieces finding their way often into waterways and oceans.
The thrown-away butt, a lethal parcel of absorbed nicotine, heavy metals and chemicals, appears to marine life as food floating on the surface. It has been found to be deadly to fish, and to inhibit plant growth. A new addition, e-cigarettes are growing in popularity, their discarded pods posing a similar problem not to mention the e-cigarette itself, a package of plastic, electric circuitry and battery.
Another disturbing trend is for manufacturers to add plastic microbeads as cheap fillers in household products like toothpaste, shampoo and cosmetics. Washed down the drain, and small enough to bypass the water filters at reclamation plants, these eventually find their way into the ocean. Of course some can be swallowed accidentally by product users. A Mother Jones (May 28, 2015) article pictures an array of products containing them.
Fish are fooled by microbeads, which are a similar size and shape to fish eggs. Add all the other plastics and the chemicals adhering to them and they become a meal with long-term consequences for other predators as well. The Guardian newspaper reports on five species affected by ocean plastics. Fish-eating birds, whales with plastic-clogged stomachs, turtles snagged by plastic six-pack holders, crabs ingesting microplastics that also enter through their gills, even vital oxygen-producing ocean bacteria, are being harmed.