Sunday, February 14, 2021

Where had all the plastic gone?

 Today, I continue to discuss assertions made entitled “Apocalypse Never” by environmental policy commentator Michael Schellenberger, whose main thesis is that our environmental problems are not really that bad.

Another topic he discussed was the impact of plastics in our environment. His main thesis is that plastics degrade quickly in sunlight (a phenomenon called photo-dissociation), because ultraviolet light breaks down the bonds that hold plastic together. 

 I will note that “degrade” is not the same as “disappear”. Plastic stuff becomes microplastic stuff. Plastics never go away, they just break apart and become small - less than 5 mm (1/8 inch), or even less, a few microns, where they become known as nanoplastics.

 Schellenberger cited a scientific study where researchers found 95% less plastic at the ocean’s surface than they expected. Where had all the plastic gone? It was broken down to microplastics onto which small plankton and bacteria attached, making the particles weigh enough to sink to the ocean floor – problem solved. Turtles with straws up their noses, sea birds and whales with stomachs containing plastic junk are an excuse for alarmism, not real problems.

 Not so fast. The amount of plastic on the seafloor is now estimated at almost 200 MILLION tons. The amount of plastic entering the oceans every year is roughly 8 million tons, equivalent to 90 aircraft carriers. Most of it will break down into microplastic or nanoplastic particles. Estimates are that about 5.25 trillion microplastic particles now float in the oceans from the surface to the depths.

 But it is only in the last few years that detailed ecological risk assessments of microplastics in the oceans or coastal areas have been performed. A risk assessment determines at what concentration a substance becomes a risk to human or ecological health. 

 One study I read found no discernible risk to life in the open ocean at current concentrations, with the caveat that the concentrations are increasing and will exceed levels which will cause problems for ocean life by mid-century. In some coastal environments, those levels have already been exceeded.

 Another study stated that microplastics can be small enough to pass into the bloodstream through the intestines, even as larger particles pass through the gut undigested. Microplastics become more and more concentrated in body tissues as they pass up the food chain from plankton to crustaceans to fish to seabirds. Limited evidence suggests that microplastics are a threat to marine animals. “Suggest” is not the same as “unequivocally demonstrate” so therein hangs the problem.

 But what about us? As microplastics are now ubiquitous in the environment, we ingest about one credit card’s worth every week or half a pound every year, the equivalent of about three smartphones. 

 Eating credit cards like Doritos, even with guacamole, goes under the heading of really bad idea, but are microplastic particles actually harmful to us? We don’t know for sure.

 Research into the toxicity of microplastics is just getting started. We do not know the effects of plastics on the human body in detail because we haven’t gone looking for them in detail. 

 Plastics are more than just the polymers. They contain several thousand other chemicals, even flame retardants. In the environment, plastics adsorb toxic man made chemicals, including polychlorinated biphenyls, polycyclic aromatic hydrocarbons, bisphenol A, and organochlorine pesticides, all of which go under the heading of “really bad for you”. We get exposed to these chemicals every day, but microplastics present a new pathway into the human body.

 Once very small microplastics are ingested, they can pass into the lymph system, and get deposited in the liver, penetrate the placenta and blood-brain barrier and the lungs. Once there, the particles will accumulate. Plastic particles can cause inflammation and inflammation underlies many human ailments. Cause and effect? We don't know.

 Initial studies in labs indicate that microplastics are indeed toxic to lung, liver and brain cells, but that’s a far cry from fully understanding their interactions within the human body. As one article stated, “It could be that, as with many pollutants, there is a threshold beyond which microplastics become toxic to humans or other species.” We just don’t know what it is yet.

 So, what are we to do? Every article and study I read had the same recommendations: First, fully understand what micro and nanoplastics do to wildlife and humans. Second, stop putting plastics into the environment. Third, start using less plastic, much less. I know, easier said than done. 

 We are in a situation where we have absence of evidence. That is not the same as evidence of absence. Ignorance is not an excuse for inaction.

“It is also within our power to change cultures so that litter created on land does not become an environmental hazard in our oceans, both now and for future generations." 

- Jason Hall-Spencer, PhD, Marine Biology

Published in the Westborough Village News, 11/14/2020

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