From Macroplastics to Microplastics: Worldwide Environmental, Wildlife, and Human Contamination. Real Solutions Urgently Needed
by Ted Schettler, Science Director
Sailing through the North Pacific gyre many years ago was like wandering through a poorly-curated community yard sale with few treasures and lots of trash—mostly plastic. It’s worse now. In the Great Pacific Garbage Patch, several oceanic currents deposit enormous amounts of debris into this expansive sea.
Most of the garbage originates on land, although mixed in is some lost or abandoned fishing gear. Estimates of the amount of plastic entering the oceans annually are highly uncertain and vary widely—from 500,000 metric tons to ten times that amount. Regardless, it’s a lot. The International Union for the Conservation of Nature determined that plastic makes up 80 percent of all marine debris from surface water to deep sediments.
According to a 2017 report from the Ocean Conservancy, most of the debris originates in several Asian countries where waste management frequently includes dumping plastic waste into rivers. But this is a misleading analysis that focuses on Asian countries and diverts attention from a major contribution of the United States.
In the United States, we generate more plastic waste per capita than any country in the world. According to the EPA, plastic waste in the United States grew from less than ten million metric tons (MMT) in the 1980s to nearly forty MMT today. Only 5-6 percent is recycled. As much as half was historically shipped overseas where it often ended up in rivers. But those exports decreased when China and several other countries stopped accepting them. Today, about 85 percent of plastic waste in the United States is landfilled and 10 percent incinerated. Exports are considered “recycling.”
Larger pieces of plastic polymers slowly break down into smaller fragments in marine, freshwater, and land-based environments. As they do, they attract wildlife who mistake them for food, ingesting pieces that can obstruct their intestinal tracts and kill them. But this isn’t the full extent of the problem. Even smaller microplastics (one micrometer to five millimeters in length) and nanoplastics (< one micrometer) (MNPs) are widely spread throughout the entire global environment, from pole to pole, the bottom of the sea to mountaintops, contaminating air, water, soil, and food chains. MNPs are continuously shed from consumer products during use, recycling, and after disposal. MNPs are even intentionally added to some personal care products.
MNPs raise health concerns since they can enter the body through inhalation, ingestion, and even skin absorption. They are comprised of varieties of thousands of chemicals used in polymer and product manufacturing as well as chemicals that they absorb from their own environments. They include toxic heavy metals, carcinogens, endocrine disrupting compounds, neurotoxicants, reproductive and developmental toxicants, and more. MNPs can trigger inflammatory reactions, oxidative stress, and metabolic dysfunction in tissues where they reside. They have been found in placentas, lungs, liver, breast milk, urine, and blood. MNPs have emerged as potential risk factors for a number of disorders, including cardiovascular disease and colon cancer, among others.
MNPs and cardiovascular disease
A recent paper published in the New England Journal of Medicine amplified these concerns. The authors reported that in a series of asymptomatic patients who had undergone removal of plaques in their carotid arteries because of arterial narrowing, those whose plaques contained MNPs had a substantially higher risk of heart attack, stroke, or death after 34 months of follow-up than those in whom MNPs were not detected.
This was a prospective, multicenter, observational study involving 257 patients who completed a 34-month follow up. One hundred and fifty of those patients had detectable amounts of polyethylene plastic in their carotid plaques and 31 of those had measurable amounts of polyvinyl chloride plastic as well. The plaques in patients with MNPs also had higher levels of inflammatory markers than in those without MNPs. Patients with MNPs in their plaques were 4.5 times more likely to have a heart attack, stroke, or death from any cause than those without MNPs over the three-year follow-up period.
This was an observational study, so we should be somewhat cautious about concluding that MNPs in plaques fully explain the results. The analysis considered other risk factors, including age, cholesterol, blood pressure, diabetes and previous cardiovascular events, but there may have been other unaccounted for differences in health and socioeconomic status among patients that contributed to the outcomes. Nevertheless, it is entirely plausible that the inflammatory response surrounding MNPs in arterial plaques would make them more friable and susceptible to rupture and arterial occlusion, resulting in a heart attack or stroke, compared to the plaques without NMPs, with higher collagen content and lower inflammatory markers.
The United Nations Gets Involved
In 2022 the United Nations Environment Assembly resolved to develop an internationally legally binding agreement on plastic pollution, including in the marine environment. The resolution requested the Executive Director of the UN Environment Program (UNEP) to convene an International Negotiating Committee (INC) to develop the “instrument,” which is to address the full life cycle of plastic, including its production, design and disposal. The intent is to complete the work by the end of 2024.
Three sessions of the INC are complete. The fourth is scheduled in Ottawa, Canada from April 24-29, 2024. A fifth session is scheduled for November 2024.
As one might imagine, this as an arduous process, with full engagement of member government representatives, petrochemical and plastics industry lobbyists and attorneys, and many different non-governmental organizations from around the world. Agendas and expectations are often in conflict.
Industry is resistant to constraints on plastic production and wants to emphasize recycling, although recycling plastics in significant amounts has not succeeded. Its representatives are supportive of what they call “advanced recycling,” which can include pyrolysis, gasification, or chemical or enzymatic degradation of plastics at end of life. Virtually all of these efforts to date have largely failed to perform as advertised and many pilot projects have closed.
Recommendations from environmental health organizations (see, for example, Protecting the Developing Brains of Children from the Harmful Effects of Plastics and Toxic Chemicals in Plastics) generally include substantial reductions in plastics production; re-design with phaseout of the most toxic plastic polymers and hazardous additives; full transparency and public disclosure of the identity of chemicals used in making plastics, including additives; assurances that disposal and recycling does not result in the release of hazardous chemicals or materials into the environment or into recycled products; and prevention of incineration of plastic waste, which leads to environmental releases of hazardous products of combustion, as a means of disposal.
Negotiations over the next six months will help determine if grotesque global plastic pollution can be curbed. We have polluted virtually every ecosystem and organism on earth with contaminants directly linked to plastics. Awareness of their dire impacts is rapidly growing. Along with climate change, to which the petrochemical and plastics industries are strongly linked, these are arguably among the most pressing environmental problems that we face.