Microplastics & Nanoplastics in the Marine Environment
Dr Ian Ellul
I will start this editorial with some staggering numbers. Every year worldwide, more than 8,000,000 tons of plastic end up in our seas. In a business-as-usual scenario, this is expected to increase to 16,000,000 tons by 2030 and 32,000,000 tons by 2050. If no action is taken our seas are expected to contain 1 tonne of plastic for every 3 tonnes of fish by 2025, and by 2050, more plastic than fish by weight.1
Microplastics are considered to comprise plastic particles ≤ 5mm which may fragment to secondary nanoplastics. These are generally considered to include plastics ≤ 100nm. The microplastics released in the ocean primarily originate from laundering of synthetic textiles [which release fibre-forming polymers], tyre tread abrasion of car tyres & city dust [including abrasion of objects such as synthetic cooking utensils and abrasion of infrastructure such as building coating].1
Biodegradation of plastic is a process that results in total or partial conversion of organic carbon into biogas and biomass associated with the activity of a community of microorganisms (bacteria, fungi, and actinomycetes) capable of using plastic as a carbon source.2 This process is temperature-dependent and, in some cases, complete degradation can only be achieved above 50°C. Such conditions are rarely met in the marine environment. In addition, the polymers most commonly used (e.g. polyethylene & polypropylene) are not readily biodegradable; they are only subjected to weathering and fragmenting into micro- and nanoplastics; these remain in the environment for hundreds of years. The micro- and nanoplastics enter the food-chain through their ingestion by zooplankton and small fish; studies have also identified sea-salt as an entry point.3 On a side-note it is also worth noting that synthetic fibres have also been detected in beer, honey, sugar and tap water.
One overlooked consideration relates to the additives which are found in plastics such as stabilisers, plasticisers, flame retardants and pigments. It is estimated that approximately 225,000 tonnes of such additives are released into our seas annually. This number could increase six-fold to 1.2 million tonnes per year by 2050.1
Against this backdrop, we must talk the talk and walk the walk. Taking Japan as an example they managed to achieve 90% recycling of plastics simply by almost eliminating the production of coloured plastic bottles for soft drinks. Previously these had blue, green or red plastic containers which, upon recycling, produced amber-coloured plastic which no-one wanted. Industry agreed to make transparent PET.
In the food-chain, the impact of nanoplastics and microplastics on humans is not well-understood. Studies are needed on the following aspects:
- The effect of microplastic and nanoplastic uptake and accumulation in humans after inhalation and ingestion, such as the embolization of small vessels, inflammation and immunoreactions;
- The impact of microplastic and nanoplastic ingestion on the microbiome;
- The amount of microplastics and nanoplastics in food and when these are transferred between trophic levels such as when fish products are used to feed poultry and livestock.
I wish to end this editorial with the following fact. A global study4 published in 2017 presented the first global analysis of all mass-produced plastic ever manufactured. It revealed that approximately 9% has been recycled, 12% incinerated, and 79% accumulated in land-fills or the natural environment. This is not the world which I want my children to live in. Everyone needs to roll up his or her sleeves and do something …
- World Economic Forum. The new plastics economy – Rethinking the future of plastics, 2016.
2. Jacquin J, Cheng J, Odobel C, et al. Microbial Ecotoxicology of Marine Plastic Debris:
A Review on Colonization and Biodegradation by the ‘Plastisphere’. Front Microbiol 2019;10:865.
3. Yang D, Shi H, Li L, et al. Microplastic Pollution in Table Salts from China. Environ Sci Technol 2015;49(22):13622-7.4. Geyer R, Jambeck JR, Law KL. Production, use, and fate of all plastics ever made. Sci Adv 2017;3(7):e1700782.