Most plastics are non-biodegradable and semi-permanent; this means that they break down from macroparticles (> 5mm in size) to smaller particles, termed microplastics (5mm–1µm) and nanoplastics (< 1 µm) (Framsenteret 2018). A 1 litre plastic bottle could break into enough small fragments to appear on every mile of beach in the entire world (International Whaling Commission (IWC) 2020).
Tyre wear is the second largest microplastic pollutant after single-use plastic (Smithers 2020). More than 200,000 tonnes of plastic particles are blown from roads into the oceans every year (Evangeliou et al. 2020, Smithers 2020). To curb microplastic emissions, the Tyre Collective designed a device that captures microplastic particles from tyres as they are emitted (Smithers 2020).
Microbeads are directly produced to be added in cosmetics and personal care products. They are used as exfoliant in soap, body scrub, toothpastes and creams. They are added to create the silky texture and increase the spreadability and lubrication. Also, the coloured microspheres are introduced to create visual appeal for customers. After use, they are washed down the drain and may not be filtered through sewage treatment plants, making their way into rivers and oceans.
Micro– and nanoplastics are turning up in all the world’s oceans, even remote areas such as the Arctic and Antarctic. These are likely the most numerically abundant items of marine plastic debris. The amount of plastic in the ocean will inevitably continue increasing as plastic production increases in turn.
Plastic components contain chemicals of concern for the surrounding marine environment (brominated flame retardants (BFR), bisphenol A (BPA), nonylphenols (NPs), and stabilizers phthalate esters (PAEs)), but also absorbs hydrophobic substances, such as polychlorinated (PCBs), polycyclic aromatic hydrocarbons (PAHs) (World Economic Forum (WEF) et al. 2016) (more information on contaminants here). Ingestion of such debris and contamination by plastic-associated toxins are dangerous for marine organisms and could impair immune function of the intestinal microbiota. Recent studies suggest that polystyrene microfibers induced intestinal microbiome dysbiosis, hepatic metabolism disorders and changes in the gut barrier function (IWC 2020).
Micro- and nanoplastics can easily be ingested by marine mammals. Their effects on marine mammals cannot be assessed easily. A study by Nelms et al. (2019) suggests that there is a possible relationship between the cause of death and the abundance of microplastics in marine mammals. Individuals that died due to infectious diseases had a slightly higher number of plastic particles than those that died of trauma and others. In fact, plastic can act as a sponge and become a vector of toxins and pathogens.
In addition to the physical damage done by any plastic itself, the ingestion of micro-plastics introduces a potential for toxicity not only to these animals but also to their predators, increasing the transfer and biomagnification of harmful chemicals. Pathogenic bacteria also move across oceans on microplastics, thus increasing pathogenic risk far away from sources. Once ingested these substances and chemicals would enter the food chain, so that the negative impact can reach mankind and end up on our plates (WEF et al. 2016).
Micro-plastics in the marine environment
A variety of wildlife, from shells, small fish, amphibians and turtles to birds and larger mammals, mistake micro- and nanoplastics for food. For instance, surface-skimming baleen whales filter enormous volumes of seawater to get their food – but with them, they also retain microplastics and microbeads (Rossi et al. 2012). These microplastics may affect the filter-feeder system inside the whale’s mouth, besides introducing a higher concentration of contaminants and microbes than krill usually carries.
Public concerns about the potential impact of micro- and nanoplastics on the environment and health have increased in the last decades. It has triggered a number of scientific investigations to determine their physical and chemical effects as well as international mitigating initiatives (see e.g., UNEP 2016 and UNEP 2019).
References
Evangeliou, N., Grythe, H., Klimont, Z. et al. (2020). Atmospheric transport is a major pathway of microplastics to remote regions. Nature Communications, 11, 3381. https://doi.org/10.1038/s41467-020-17201-9
International Whaling Commission (IWC). (2020). Report of the IWC Workshop on Marine Debris: The Way Forward, 3-5 December 2019, La Garriga, Catalonia, Spain. SC/68B/REP/03. Available at https://archive.iwc.int/pages/view.php?ref=17025&k=
Nelms, S.E., Barnett, J., Brownlow, A. et al. (2019). Microplastics in marine mammals stranded around the British coast: ubiquitous but transitory? Scientific Reports, 9, 1075. https://doi.org/10.1038/s41598-018-37428-3
Rossi, M.C., Panti, C., Guerranti, C. et al. (2012). Are baleen whales exposed to the threat of microplastics? A case study of the Mediterranean fin whale (Balaenoptera physalus). Marine Pollution Bulletin, 64(11), 2374-2379. https://doi.org/10.1016/j.marpolbul.2012.08.013
Smithers, R. (2020). Device to curb microplastic emissions wins James Dyson award. The Guardian (17 September). Available at https://www.theguardian.com/environment/2020/sep/17/device-to-curb-microplastic-emissions-wins-james-dyson-award
World Economic Forum (WEF), Ellen MacArthur Foundation and McKinsey & Company. (2016). The New Plastic Economy – Rethinking the future of plastics. Available at https://www.ellenmacarthurfoundation.org/assets/downloads/EllenMacArthurFoundation_TheNewPlasticsEconomy_Pages.pdf