Plastics are everywhere; they are in your washing machine, they flow through your tap water, they accompany urban dust and they decorate the insides of your favourite seafood. Just like a pandemic, or a transnational corporation, microplastics have spread into “every crevice on Earth”, according to National Geographic.
What exactly are they? Where do they come from? How worried should we be?
Classifying Microplastics and Microfibres
In general, microplastics are small fragments of plastic that are between 1 μm to 5 mm in length. There are two types of microplastics: primary and secondary. Primary microplastics are pieces of plastic that have been specifically designed to be small for commercial use. They are used in cosmetics and personal care products, such as facial cleansers, and are estimated to make up 15-31% of microplastics in the oceans. Secondary microplastics, on the other hand, are created through the disintegration of large plastic pieces through weathering by land or sea or through photodegradation (the breakdown of material by ultraviolet light). Secondary microplastics make up 69-81% of microplastics found in the oceans.
Microfibres are defined as synthetic fibres derived from raw materials such as petroleum. They are extremely small in diameter (less than ten micrometres).
Some Unusual Sources of Microplastics and Microfibres
Usual sources of plastic (especially secondary microplastics) are very easy to point out. These include cigarette butts, plastic bottles, bags and straws- but there’s more to this than what meets the eye.
Synthetic fibres account for 60% of our clothing materials; these include polyester, acrylic and nylon. The fibres are essentially types of ‘plastic’. When our garments undergo cleaning in a washing machine, these fibres (known as ‘microfibres’) shed from the garments and are washed down the drain. Different estimates of the amount of microfibre shedding exist and many academics vary in their presentation of the data, meaning some provide estimates of the amount in kilogram, while others provide estimates in the amount by the number of strands. For example, a paper in the Environmental Science & Technology journal estimated that 372.3 kilograms of fibres are produced by a population of 100,000 people annually. In an interview with Peter Ross (vice president of Ocean Wise), Ross revealed that one load of laundry could release 10 or 12 million microfibres. It is important to note that the amount of shedding in a washing machine depends on factors including but not limited to the types of detergents used, temperature, water amount and time of washing.
What happens to the microfibres once they have been washed down the drain? There are two pathways for its release into the environment.
Their journey starts at wastewater treatment plants (WWTPs), which are defined as infrastructures that utilise physical, chemical and biological processes to remove contaminants from wastewater and eventually discard it in local waterways. WWTPs were not designed to capture plastics, however, they have been proven to catch between 60-99% of microplastics and microfibres. The amount it captures depends mainly on the technology of the WWTPs. The first pathway for microfibres to enter the ocean and freshwater systems is by passing directly through these plants (especially those with low rates of capturing microplastics effectively). Although this pathway introduces significantly less microplastic into the environment, one study concluded that ‘the small fraction of microplastic released factored with large treatment volumes equates to a significant environmental source of microplastic’.
What happens when microplastics meet effective WWTPs? Does the problem stop there? WWTPs produce a by-product called sewage sludge, which is, according to The Center for Food Safety, filled with ‘toxic compounds, nanomaterials, hormones, and dangerous pathogens’, and during the new era of plastic, sewage sludge is also contaminated with microplastics. For example, in 2013, California had 19% of all sewage sludge used as landfill cover and 56% (after further treatment) was used as land fertilisers. Since microfibres are small and lightweight, once reintroduced into the environment, they can be further moved by wind or water.
Cosmetics and Personal Care Products
Microbeads (made of plastic) are used in personal care and cosmetics products (PCCPs) such as shampoos, toothpaste, body washes and lipstick. These act as exfoliants or bulking agents in the products. As claimed by Cosmetics Europe, 4360 tonnes of microplastic beads were used in PCCPs. In the context of exfoliants, these microbeads have replaced natural substances, such as organic powders and crushed shells, as they are cheaper and more durable. In extreme cases, it was found that the plastic amount from the microbeads in an exfoliating shower gel can equal that of the plastic packaging itself. Once microbeads are washed down the drain, they undergo a similar life cycle to the microplastics from the washing machine effluent.
This source of plastic has received tremendous attention from governments and citizens globally. One notable influencer in the ‘fight against microbeads’ was the Beat The Microbead (BTMB) campaign. This campaign succeeded in persuading Unilever to remove microbeads from their products and this was also adopted by Johnson & Johnson and L’Oréal, and many countries have banned microbeads being used in PCCPs.
Potential Impacts of Microplastics and Microfibres
Microplastics pose a potential threat to marine and human health, as they can contain two types of harmful chemicals. The first being additives and the raw materials from which they were made, and the second being chemicals from their surrounding environment that are absorbed onto their surface.
Synthetic fibres as a final product are classified as safe and inert, however, the actual monomers and additives that make up these fibres are usually poisonous, carcinogenic (cause cancer) and explosive. Not all monomers and additives are chemically bound to the microfibre matrix, which means they can leach out into the oceans or into the organisms that ingest it. This process will expose marine organisms to potent chemicals such as bisphenol A and phthalates, which (even at very low concentrations) can interfere with hormonal functions in marine organisms and humans. In addition to this, when microplastics are discarded into the ocean, they join an already existing ecosystem of pollutants, which includes persistent organic pollutants and heavy metals. Microfibres from washing machines possess a high surface area, meaning that large volumes of toxic and poisonous pollutants can attach and accumulate onto their surface.
Numerous studies have indicated that our seafood is contaminated with synthetic fibres. For example, 63% of brown shrimp that were captured in the Southern North Sea and 38% of commercial fish captured from the Mondego estuary in Portugal contained microfibres. When humans digest contaminated seafood, they are subject to potential pathways for microplastic toxicity.
A review paper published in February of 2020 outlined the routes of exposure of microplastics and the multiple pathways for microplastic toxicity.
Microplastics can cause a phenomenon in the body called oxidative stress, which is when the microfibres release so many free radicals to the point where the body cannot produce enough antioxidants to counteract it. This leads to the development of neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease, cancer and heart failure. Microplastics can also alter metabolic functions. For instance, the exposure of microplastics in mice causes a decrease in ATP levels in their livers, and it has been speculated that this phenomenon is observed in humans, decreasing their energy levels.
Should we be Worried?
Due to our heavy reliance on plastics, it is no doubt that they have found their way into almost every place on earth (even remote forests), but it is important to remember that research into the effects of microplastics is still very new and limited. The ‘potential dangers’ of microplastics have been inferred by limited data from animals observed in lab environments. Where we should go from here is summarised in a quote from The Guardian by Christian Dunn at Bangor University:
“Microplastics are being found absolutely everywhere [but] we do not know the dangers they could be posing. It’s no use looking back in 20 years’ time and saying: ‘If only we’d realised just how bad it was.’ We need to be monitoring our waters now and we need to think, as a country and a world, how we can be reducing our reliance on plastic.”