Plastic is a remarkable material that has forever changed our societal expectations regarding the quality of our food, water, health care, safety and products that improve our lives every day. But all good things remain good within limits. For many years now there has been growing recognition that, because plastic does not degrade like natural materials, it is now present everywhere and our approach to plastic must change. As a result, we’ve seen China’s 2018 rejection of plastic shipments, the May 2019 Basel Amendments to list plastic waste, and while industry, DOE and NGOs have tried to get ahead of the issue, a recent global wave of single-use plastic bans,.
We know that we need to turn off the tap of plastic waste leaking into the environment, both macro and micro plastic, through “reduce, reuse and recycle,” and then turn to mopping up the floor. First on the list for turning off the tap: single use plastics. They are ubiquitous in daily life, yet generally are not reused and likely, as a result, represent most of the ocean waste we see. Hence, the single-use plastic bans, though some sector stakeholders, like healthcare, may figure out how to capture post-single use plastics in sector-specific circular economies (managing material from cradle-to-cradle as in closed-loop recycling).
Other sources of environmental plastic are tougher to address, especially microplastics. Microplastics can be created when macroplastics fracture into smaller pieces, so all macroplastics potentially have a future as microplastic. However, the majority of microplastic appears to come from ubiquitous consumer products, such as shreds from tire wear, microfibers from polyester, rayon and other fabrics, and particles from latex and other coatings. The only way to reduce microplastics from these sources may be to reduce plastic in the source itself.
Moving on to recycling, it is evident that, even after collection, cleaning and sorting, recycling is a challenge. Single types of plastic are themselves heterogenous. For example, polyethylene terephthalate (PET) used for a soda bottle is quite different than the PET used for a take-out container. And then there are the additives. Post-use plastic’s variability would render it “inherently waste-like” pursuant to EPA’s “legitimate recycling” factors in Sylvia Lowrance’s 1989 RCRA guidance. Like most inherently waste-like material, post-use plastic currently lacks sufficient value to reliably support management as a product sufficient to keep it out of the environment. Turning off the tap will therefore necessitate different approaches for manufacturing and use, including potential reformulation of current products within defined circular economies to both mitigate sources, increase homogeneity and boost the value of post-use plastic to support financially viable recycling.
Turning to mopping up our floor, our environmental mitigation and remediation tools in the United States are generally triggered by acute or chronic chemical toxicity; plastic is generally inert and not recognized as posing such a threat. Potential imperfect approaches to addressing plastic pollution now, as simple categories of solid material, include: PM2.5 under the Clean Air Act (CAA); turbidity under the Safe Drinking Water Act (SDWA); total suspended solids or other pollutants under the Clean Water Act (CWA); solid waste under Solid Waste Disposal Act (SWDA) (though litter is generally left to municipalities); and as a source of hazardous substances, if not a hazardous substance itself, under the Comprehensive Environmental Response, Compensation and Liability Act, (CERCLA). The Toxic Substances Control Act (TSCA) and the European Union’s Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) generally exempt plastics due to their high molecular weight and inert nature.
New policy and legal authority may be helpful, but we still have work to do in hazard assessment. Although generally chemically inert, plastics may still pose physical risk. Evaluating physical toxicity sufficient to define a reference dose, or exposure assessments similar to asbestos, may allow application of traditional risk-based approaches as we would other environmental pollutants. Progress is being made in this direction. In February, the National Academy of Sciences gathered international experts to discuss microplastics, potential effects on human health, options for mitigation, and ways to leverage new approaches to inform public health and policy decisions. As we learned, plastics break down into unique shapes, based on their molecular structure and use, which may pose different hazards based on their shape and size. Further research will allow development of approaches that can be used to develop action thresholds and reassure the public regarding acceptable concentrations. Defining the possible scope of potential harm, including when plastic may eventually break down completely and become “mineralized,” will assist in applying existing authority as well as developing new authority.
In addition to defining risk, there have been increasing commitments toward better defined circular plastic supply chains and technological innovation in plastic recycling (including electrifying plastic into instant graphene, which raises its own issues), as well as project funding and other federal and state legislative responses to the issue of plastic waste including public education. The push and pull of progress continues on all fronts, with consumer activism expediting the timeline.