What are microplastics?

Plastic is a solid, synthetic material made from oil and gas, or renewable organic material from plants. It is the third most abundant material after concrete and steel, and is hugely important for society due to its uses in many different sectors, including medicine, construction, food packaging, electronics and transport.


Microplastics are microscopic pieces of plastic debris. You need the help of a microscope to see most of them, although the formal definition includes plastic particles up to half a centimetre – big enough to see with the naked eye.

Where do microplastics come from?

Many different places. Microplastics shed from plastic litter due to sunlight exposure, which causes the material to weaken over time and fragment. They’ll also come from plastic items because of wear and tear.

Due to the wide range of plastics, applications and forms, microplastics are found in a variety of shapes and types. In fact, up to 1.5 million microfibres, which are a microplastic, can be released per kilogram of clothing during a wash. Even opening a plastic bottle or plastic packet can create thousands of microplastics.

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Microplastics move throughout the environment via both human and natural processes. For example, the microplastic fibres released from your clothes during laundering are rinsed down the drain where between 72 to 94 per cent is captured in sewage sludge during wastewater treatment. This sludge is then applied to the land as an important soil conditioner.

Winds can mobilise the soil in dry conditions, potentially blowing the microplastics away. This can also happen to microplastics polluting roads, cities and the surface of the oceans, distributing them far and wide. The complexity of microplastics’ sources and journey as they cycle through the Earth’s environments means they are incredibly challenging for both scientists and environmental managers to study.

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How widespread are microplastics?

Over the last few decades, the evidence on the extent of microplastic pollution has been growing. Originally perceived as a marine issue, with an estimated 15 to 51 trillion microplastic particles floating on the ocean’s surface, scientists have recently discovered they also contaminate rivers, soils and air.

They have even found their way into some of the most remote regions, including the poles, the equator, the deep ocean floor and even Mount Everest.

Are humans ingesting microplastics, and if so at what rate?

The short answer is: yes, with the discovery of microplastics in human stool confirming this. Microplastics have been found in a range of food and drinks, mostly bottled and tap water, shellfish and salt. They’ve also been measured in indoor dust, which may settle on our food and drinks.

Current high-end estimates of the rate of ingestion range from 52,000 to billions of microplastics per year. However, the food groups investigated by most researchers represent a very small amount of the average adult’s diet. There are many food types which we consume a lot of that haven’t been investigated yet, such as cereals, and so it is hard to get a clear picture of exactly how many microplastics we are consuming.

Are microplastics harmful?

There currently isn’t enough evidence to say, because this is a relatively new topic and researchers are still building the evidence base. It is plausible that microplastics cause harm, as other particles can do, but the differences between the nature of microplastics compared to these particles leaves uncertainty.

There is some experimental evidence emerging to suggest that ingestion of high levels of polystyrene beads affects the reproductive system in rats and mice, but what is causing this and how relevant this is to real-life microplastic exposures is unknown. It’s likely that the very smallest particles have the greatest potential to cause harm, but quantifying these and understanding where they come from is a challenge.

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What can we do to limit our exposure to microplastics?

While the debate is still ongoing as to whether microplastic could cause harm, you may still wish to limit your exposure. Drinking filtered tap water and choosing natural-based products over plastic for yourself and your environment will help to reduce your microplastic exposure.

Ultimately, minimising everyone’s exposure requires a global effort to limit microplastic release to the environment. Things you could do to contribute to this include avoiding single-use plastic while shopping (and bringing your own bag); reducing your plastic waste; washing your clothes less often and using a laundry bag to catch some of the fibres which go down the drain.

When in doubt, I try to stick by the ‘5 Rs’: refuse, reduce, reuse, repurpose and finally, recycle. Whatever the solution, it’s important that it’s better for both the planet and people.


About our expert, Dr Stephanie Wright

Stephanie is a lecturer at the Medical Research Council. She has more than nine years’ experience in the field of microplastics, specifically exposure and biological impacts.


Stephanie is a lecturer at the Medical Research Council.