1. Introduction
Plastics are wonder materials that have enabled the creation of the modern, industrialized world. They are manufactured on a truly massive scale (almost half a billion tonnes each year), but much of this is for single-use applications, which both fuel and urge our throwaway culture. As a consequence, plastic waste is a vast and growing problem, in part due to the robustness of plastics, meaning that they degrade only slowly in the environment and tend to break down into increasingly smaller particles, namely microplastics (MPs) and nanoplastics (NPs). These threaten the health of ecosystems and organisms that inhabit them, including humans. Toxic chemicals associated with plastics and their uses pose further adverse health effects.
Although John Wesley Hyatt, who introduced nitrocellulose to make billiard balls from, instead of ivory, is said to have remarked that, “in spite of their tendency to catch fire, cellulose nitrate saved the elephant”, the cumulative mass of plastics made by humans now exceeds the total mass of all living animals on Earth. Research from the Stockholm Resilience Centre concluded that plastics impact adversely upon all nine planetary systems—including climate change, ocean acidification, biosphere integrity, freshwater change, and land-system change. Harmful effects are delivered across the entire life cycle of plastics, beginning with fossil fuel extraction and polymer production, through to environmental degradation and MP/NP dispersion into the atmosphere, deep oceans, and living organisms.
2. Plastics and the consumer society
The proliferation of plastic materials in society is a consequence of their ease of production and cheapness, along with durability and strength, but low mass, as compared to other materials, such as metals. Thus, road vehicles may be made from up to 20%, by weight, of plastics. For the Boeing 787 “Dreamliner” Jumbo Jet, the proportion is around 50%, which means that the fuel needed to be burned for each flight is reduced by 20%, in comparison with a similar-sized aircraft made from traditional materials, such as aluminum. The use of plastics in packaging and for medical applications has resulted in improved healthcare and food safety, while savings in energy and costs are a further advantage of using them, for example, in place of glass or metals. The availability of cheap plastics has unleashed a flood of consumer goods across the world, overcoming many of the physical limits and supply constraints of their natural equivalents, and placing otherwise expensive items into the hands of citizens ranging across the socioeconomic spectrum.
Bakelite was introduced in 1907 by Leo Baekeland, and this could be heat-moulded into numerous consumer products; of particular importance being radio sets (thus made available in most households), furniture, and other objects, including telephones, vehicle parts, washing machines, toothbrushes, combs, cutlery, drinking vessels, and ashtrays, to list just a few. In 1938, Nylon was first used to make bristles for toothbrushes, being featured at the 1939 World’s Fair. Nylon became an iconic feature of the 1940s period, in the form of “nylons”, as substitutes for the more expensive silk stockings.
Famously, in 1955, Life magazine published an article on “Throwaway Living” that featured a picture of a family throwing a range of kitchen and other household items into the air, noting "The objects flying through the air in this picture would take 40 hours to clean—except that no housewife need bother. They are all meant to be thrown away after use". This is often cited as the dawn of what is now referred to, mainly dismissively, as the “throwaway society”.
Given that the presence of plastic items, objects, and devices is ubiquitous in the modern age, plastic has been proposed as a distinctive stratal component and a possible critical geological indicator of the Anthropocene.
3. Microplastics
Primary microplastics (MPs) are those originally manufactured at the (<5 mm) sizes in which they are found in the environment, for example, microbeads, and nurdles from which plastic items are made. Secondary microplastics are formed by the degradation of larger plastic items, including bottles, to hold water and other drinks, plastic bags, and fishing nets. There is, nonetheless, some controversy over whether certain MPs should be considered primary or secondary; for example, particles from the wear of vehicle tyres on road surfaces and microfibers from washing textiles. However, Song et al. have proposed that this can be resolved by using the classifications “intentional” and “unintentional”, so that primary MPs are those actually manufactured at <5 mm dimensions, while all others can be categorized as “secondary”, having broken down from larger objects, or painted areas, including road markings, ships, and bridges.
MPs have been found wherever they have been sought, e.g., in the air, rivers, aquifers, mountains, glaciers, soils, Arctic sea ice, insects, drinking water, food (honey, sugar, salt, beer, seafood), the oceans and ocean sediments, including waters and deep sea sediments around Antarctica, and in the depths of the oceans. Atmospheric transport has been identified as a major transfer route for MPs to remote regions, for example, the Arctic. MPs can be transferred through different life stages of mosquitoes that use different habitats and can thus be potentially transferred from aquatic systems by flying insects and those that feed on them, spreading them even further.
It has been estimated that, in 2019, there were 82–358 trillion plastic particles, primarily MPs, floating in the world’s oceans, with a total mass of 1.1–4.9 million tons, and that a rapid increase had occurred since 2005.
Exposure of plastic items to the erosive forces of the outdoor environment, e.g., polytunnels, agricultural films (mulches), construction materials, and vehicles, also generates secondary MPs. The most effective long-term solution to the microplastic (MP) problem is to reduce overall plastic consumption, since MPs, once formed, are extremely challenging to remove from the environment.
4. Nanoplastics.
Although definitions vary, nanoplastics (NP) may be characterized by a size of less than 100 nm in at least one dimension. NPs are either considered to be short-lived entities resulting from the fragmentation of MPs, or that their concentrations are actually high and constitute a significant environmental threat; this ambiguity being the result of difficulties in detecting them.
Due to their small size, NPs can penetrate the tissues and organs of living creatures, potentially resulting in harmful biological effects. NPs can be formed by the mechanical breakdown of commonly used polystyrene products, such as coffee cup lids and expanded Polystyrene foam. Toxicity, varying with particle size, has been demonstrated in zooplankton, along with size-dependent uptake in these and other aquatic organisms. NPs have been shown to traverse food webs, ranging from algae, zooplankton, and planktivorous fish to piscivorous fish, potentially causing changes in the behavior and metabolism of the fish along this feeding chain.
5. Environmental and human health impacts of plastic pollution
Millions of sea animals and birds are killed each year by entanglement or ingestion involving larger plastic waste items. Overall effects of MP/NPs on ecosystems and food chains are likely to be detrimental. Plastic items have been found in the stomachs of seabirds, sea turtles, seals, whales, and fish; MPs have been identified in the tissues and organs of a range of marine creatures. Plastic is harmful to corals as a consequence of light deprivation, the release of toxins, and anoxia, which encourages pathogen invasion.
Leachates from plastic items, such as HDPE bags and PVC matting, can impair growth and oxygen production from Prochlorococcus, which is the most abundant photosynthetic bacterium in the ocean. Thus, the ability of the oceans to absorb carbon dioxide may be further impeded.
There is evidence that MPs may be present throughout the entire water column of the oceans. This is highly significant, since in marine environments, MP/NPs pose a direct danger to plankton and other key Earth ecosystems, including mangroves and coral reefs. Since MPs may further serve as vectors of major ocean pollutants, an additional hazard to marine ecosystems (and humans) is presented. Bisphenol-A (PBA), plasticizers, and other related materials have been identified in the bodies of humans and other animals, which may act as endocrine disruptors. Possible human health effects of MP/NPs have been identified, including their potential to induce inflammation, oxidative stress, apoptosis (cell death), and metabolic homeostasis (leading to obesity).
In The Lancet Countdown on health and plastics, it was emphasized that we are in the midst of a “plastics crisis”, as this is a “grave, growing and under-recognized danger” to people and the planet, causing “disease and death” from infancy to old age. The authors note that plastics damage human health through a matrix of influences, including direct exposure to landfills or chemical plant emissions, environmental contamination, absorption via food packaging, microplastics, air and soil pollution, and the burning of related fossil fuel feedstocks. Such health consequences range from birth defects and microplastic poisoning in the womb, to asthma, cancers of various kinds, heart attacks, hormone disruption, and developmental problems. It has been estimated that the average human brain may contain 7 grams of MPs and NPs.
MPs can affect the transport, fate, transformation, and bioavailability of contaminants in soils and further threaten food security and human health. Furthermore, the structure, diversity, and functions of soil microbes are all affected by MPs at high concentrations, while plastic debris can be ingested by soil fauna, with consequent detrimental effects. In one study, when sewage sludge was applied to soil over a period of 5 years, the soil MP levels were found to increase by 1450%; hence, MPs should be considered along with other types of pollution (such as heavy metals) that can be transferred to soils. Furthermore, MPs are shown to be directly toxic to earthworms, which are keystone species and ecosystem engineers in soil. Thus, long term damage to food systems is a likely legacy of MP pollution.
6. Plastics recycling
Only 9% of manufactured plastic is actually recycled. A major impedance to recycling is actually economic, since it is often cheaper to make new (“virgin”) plastic than it is to recycle it; accordingly, investment in better recycling infrastructure and technology is not sufficiently encouraged, thus maintaining the pattern of low recycling rates. Thus, as an essential means to encourage greater recycling of plastic waste, it is necessary to increase its value, as compared with virgin materials.
From a mathematical study, it was demonstrated that the only way to reduce the amount of plastics that finally end up in landfill or are incinerated is to produce less plastics in the first place: what is not created does not need to be disposed of. Thus, recycled material must displace primary production, but since this is driven by market forces, there is no guarantee it will happen. To assume, incorrectly, that all recycled plastic avoids disposal underestimates the environmental impacts of the product system. It is proposed that “scholars and policy makers should focus on finding and implementing ways to increase the displacement potential of recyclable materials rather than focusing on disposal diversion targets”.
7. Plastics we can’t (easily) manage without
To reduce our use of plastics will require fundamental behavioral (and societal) changes, but for the most part, it would be best to reserve them for those purposes where they are not easily replaced by other materials. That we cannot live entirely without plastics is the subject of an article from the think-tank Chatham House, which once again emphasized their criticality for healthcare, food safety, and other safety applications ranging from cycling helmets to electrical insulation. However, a hugely complex variety of plastics is currently being produced, often not in forms that can easily be recycled.
The report proposed that the number of plastics produced be reduced to perhaps 10–20 key polymers, which can be easily identified, sorted, and recycled, from the thousands now available. However, resistance to this strategy is to be expected, since it would reduce profits for the fossil fuel industry, as primary producers, and for others who rely on a rapid turnover business model, such as fast fashion or “on-the-go” consumables such as disposable cups.
Some of the many specific uses of plastic that cannot (easily) be avoided include sterile, single-use medical items such as surgical gloves, syringes, IV bags and catheters, vaccines and bandages, PPE facemasks, and protective clothing (i.e., as used during the COVID-19 pandemic). Sterile storage and lightweight transport of medicines and medical supplies, including vaccines and bandages, are also facilitated by plastics, although the absolute necessity for their use throughout the healthcare system has been challenged.
8. Behavioural changes
Since plastics are such a deeply entrenched feature of our modern, consumer society, to avoid them entirely seems a remote prospect, at least without drastic changes to the fabric and mechanism of that society. While finding a single solution may be difficult, by integrating different voluntary behavioural change strategies, the problem of overconsumption might be addressed, with plastic reduction as part of a broader aspect of reducing materials use and waste production (“human ecological overshoot”).
The broader picture of systemic human behavioral traits and the polycrisis has been addressed, of particular importance being those which have become maladaptive in the context of modernity; in particular, warfare, resource overexploitation, and human cognitive biases. On the basis of key literature articles, behavioral traits are highlighted that underpin these maladaptations, and which are further proposed to offer leverage points in the global system where the likelihood of a polycrisis might be alleviated.
Similarly, it has been identified that the root of human ecological overshoot lies in a (maladaptive) behavioural crisis, driven in part by advertising, but that those same mechanisms may also provide means for throwing into reverse three “levers” of overshoot—consumption, waste, and population. The authors further identified that a gulf in communication exists, “between those that know, such as scientists working within limits to growth, and those members of the citizenry, largely influenced by social scientists and industry, that must act”. Hence, bridging this discontinuity is an essential strategy for making necessary systemic changes.
9. The oil, plastics, energy nexus
Since the vast majority of plastics are derived from fossil sources, mainly coal (44%) and petroleum (40%). It has been argued that the recent dramatic increase in plastics production is part of a deliberate strategy by multinational fossil-carbon corporations, which, in integrated form, produce coal, oil, and gas and additionally manufacture plastics. Thus, while there is a reduction in the production of fossil fuels per se by particular enterprises, their manufacture of plastics is increasing in order to maintain and expand the overall product base.
The Ellen MacArthur Foundation’s “New Plastics Economy” report concluded that, in 2014, the plastics industry consumed 6% of the global oil supply (including natural gas liquids). They further estimated that, in 2050, 20% of the world’s available oil supply will be consumed by making plastics. However, such reasoning assumes that the oil supply will remain sufficiently robust for these projections to be realized, which is not guaranteed, as a result of limitations in global oil production. Evidence has suggested that growth in the global oil supply is being substantially maintained by fracking, mainly in the US, but this industry may not be able to sustain its output, leading to a supply downturn at some point from 2025 to 2030.
Geopolitical influences, such as constraints in the passage of oil through critical points, such as the Strait of Hormuz which had formerly carried 20% of global traded oil, and potentially, the Bab al-Mandeb strait, will likely add further complexity to the picture.
Future such restrictions may limit how much plastic can actually be made, given other demands for fossil fuels, as well as considerations over reducing greenhouse gas emissions. The implication, therefore, is that, along with limits to possible bioplastics production, there may be less plastic available overall, which, therefore, should be “saved” for critical applications where there is no ready substitute, e.g., medical/healthcare industry, electronics, clean water, clean medicine, and clean food.
10. The broader context
In 2019, 460 Million tonnes (Mt) of plastic was produced, a number projected to reach 1,230 Mt by 2060. Plastic waste amounts to more than 400 Mt/a, roughly half from single-use items such as packaging, a number that is expected to exceed 1,000 Mt by 2060. By 2050, 20% of the world’s oil supply is predicted to be consumed by plastics, along with 15% of the global carbon budget.
Microplastics (MPs) cannot be avoided entirely, so long as we keep using plastic materials that go through a wear and tear process, including vehicle components (tyres, brakes, upholstery, etc.), road markings, marine coatings, clothing, paints, agricultural films, and synthetic textiles. Plastic pollution poses significant and grave health risks, impairs biodiversity, and contributes to emissions/climate change along the entire “cradle-to-grave” chain. Consequent damage to ecosystems impairs their ability to absorb carbon, e.g., phytoplankton and soils.
While the amount varies from region to region, on a global basis, merely 9% of plastic waste is recycled. A more effective interception and collection of plastic items after their use is critical to reduce their environmental burden. End-of-life aspects need to be designed into a plastic item when
it is created. Contaminant materials that make recycling difficult should be avoided. As an essential means to encourage greater recycling of plastic waste, it is necessary to increase its value, as compared with, currently cheaper, virgin materials.
Plastic waste should be ameliorated, mainly by curbing the overall use of plastics per se, through the approach: Refuse, Reduce, Reuse, Repurpose, and Recycle (as a last resort). Wasteful (unnecessary) and single/short-term-use plastics, especially disposable packaging, must be minimized. Limits to the production of bioplastics, along with an ultimately declining supply of fossil fuels, suggest that relentless expansion in the availability of plastics may, in any case, be unlikely, and that a combination of more effective use, material substitution, and behavioral changes is the more viable way forward. Plastics should be “saved” for critical applications, where there is no ready substitute, as in healthcare, food/water provision, and electronics.
This approach also accords with the need to respect overall resource limits and planetary boundaries. Means to leverage behavioural changes regarding consumption patterns are required to bring humankind to below ecological overshoot, into the realm of “one planet living”, and begin healing the current polycrisis.
Achieving a sustainable future also likely involves living in a more locally focused way, including local, place-based food growing. This will further reduce both the need for plastic packaging and MPs emissions from vehicles, along with a lower dependence on food imports and other supply chains, which may fail as a result of climate change impacts on agriculture and eventual restrictions to the global oil supply.
