Microplastic and nanoplastic pollution threatens our environment. How should we respond?

The 1907 development of Bakelite, which was the first mass-produced plastic used as an electrical insulator, sparked our dependence on synthetic polymers. Bakelite was durable, heat-resistant and could be reshaped into many forms. These properties led to the development of a range of cost-effective synthetic polymers that have enabled major advances in technology, medicine and food distribution and storage.

Our total plastic production to date has reached 8.3 billion metric tonnes. The majority of that is still present in the environment. Annually, 91% of plastic produced is not recycled. It ends up in waste sites and in our oceans. In 2017, an average of one dump truck of plastic waste was disposed of in our oceans every minute, and this figure is expected to rise in coming years.

The environmental impact of our addiction to plastic is evident globally, and has led to serious health and environmental concerns. Research shows that 83% of tested tap water samples globally were contaminated by plastic microparticles. Microplastic can be also found in 93% of bottled water, as well as in soil and even human bodies. Other man-made organic compounds, such as per- and polyfluoroalkyl substances (PFAS), have also been found in human blood.

In January 2018, the European Union signed the first ever strategy to promote a circular economy for plastic. It will deliver a review on nanoplastic and microplastic pollution in late 2018. Similar strategies have been proposed by the United Nations and Global Plastics Associations, with the aim of reducing plastic waste through effective recycling schemes; through the use of alternative feedstocks, in an attempt to defossilize plastic production; and through careful regulation of single-use plastic products.

Despite increasing awareness of the global impact of plastic waste, our dependency on plastic is unlikely to change due to its invaluable properties. As a result, research into biodegradable plastics has risen in recent years, with many companies advertising compostable or degradable plastic products.

Unfortunately, many of these products are only degradable in specific environments. Their degradation can also result in waste products that present an equally significant threat to the environment, as evidenced by the effects of microplastic. This could suggest a policy injunction around what can be classified or advertised as "biodegradable", as consumers willingly buy and support these products in the hope of reducing harmful pollution, yet they have little or no effect.

A variety of degradable plastics made from bio feedstocks, known as bioplastics, are in development. These safely and fully degrade, as a result of being produced from sources such as cassava or seaweed. Similar reports of utensils made from edible feedstocks bring into question the feasibility of large-scale production of these materials, especially when the 2018 UN Global Report on Food Crises estimates that 124 million people face food insecurity.

A promising alternative to these materials has been developed by Newlight Technologies, a company that makes bioplastic from sequestered carbon emissions known as AirCarbon. This method produces a naturally occurring biopolymer from carbon-based greenhouse gases, effectively replacing fossil fuel-based synthetic polymers with bio alternatives, while decreasing greenhouse gases in an overall carbon negative process. Newlight Technologies is working to launch their product in a range of market sectors, providing hope that we can harness greenhouse emissions for the large-scale production of usable materials.

Progress in the development of sustainable and biodegradable materials to replace synthetic polymers notwithstanding, we must still ask: What can be done to tackle the millions of tonnes of plastic waste present in our ecosystems? Although there is widespread awareness of the importance of recycling, current strategies only result in 9% of the plastic produced every year being recycled.

One pioneering study to improve current recycling methods is led by Professor John McGeehan and Dr Gregg Beckman from the University of Portsmouth and the US Department of Energy’s National Renewable Energy Laboratory (NREL). While studying a naturally occurring bacterial enzyme (PETase) capable of degrading polyethylene terephthalate (PET) - the most commonly used plastic - they serendipitously discovered a genetically engineered derivative of the enzyme that is more efficient at breaking down PET as a food source.

Professor McGeehan noted that "although the improvement is modest, this unanticipated discovery suggests that there is room to further improve these enzymes, moving us closer to a recycling solution for the ever-growing mountain of discarded plastics". This pioneering study may lay the foundation for subsequent studies into the design of genetically altered enzymes that enable the degradation of plastic waste products. However, the possible consequences of large populations of microorganisms containing such enzymes are still unknown.

The environmental impact of plastic waste is widespread, and it requires large-scale plans to minimize its effects. The establishment of strategies to tackle these issues is encouraging, but there is a lack of legislative measures and policies regarding the resulting innovations such as degradable (bio)plastics and genetically engineered plastic-degrading enzymes. This may prevent these technologies from realizing their potential, or it could result in alternative undesirable degradation products entering the environment.

Improved standards around what is considered and advertised as biodegradable should be considered. A better understanding of the knock-on effects of our attempts to reduce the environmental impact of our addiction to plastic is needed. It calls for the careful design of policies to ensure that the goals of strategies developed by the European Commission, United Nations and Global Plastics Associations are met effectively and safely.