Should we be worried about microplastics?

Microplastics have been found by scientists in all corners of the earth, from remote polar regions to the sediment of the Mariana Trench. They’ve been found in fruit and vegetables, meat, seafood and our water supply, as well as in the air we breathe. Studies have found them deep in the lungs, in our bloodstream and brains.

It’s estimated that, each year, up to 40m tonnes of microplastics leak into the environment globally, and this is expected to double by 2040. So there’s no doubt that they are in our environments, homes and bodies – but the bigger question is what impact they’re having there. 

This feature appears in the September issue of Which? Magazine. Join Which? to get our monthly magazine, or if you're already a digital Which? member, add the magazine to your membership in your online account or by calling us on 029 2267 0000.

The harm of microplastics

There is strong evidence that microplastics cause significant environmental harm. They can interfere with the ability of small organisms and plants to store carbon. This disrupts the blue carbon cycle – the carbon stored by marine life – which is critical in mitigating climate change. 

The evidence for their impact on human health is less established. However, lab studies suggest that they can cause oxidative stress (an imbalance between free radicals and antioxidants in the body), which canlead to cellular and tissue damage, disruption of the gut microbiome and immune or inflammatory responses. 

Despite much of the human health evidence only beginning to emerge, many scientists agree that it’s worth taking a precautionary principle when it comes to our microplastics exposure – that is, avoiding and reducing it where we can. 

The University of Portsmouth’s Global Plastics Policy Centre believes there is an urgent need for a UK microplastics policy. There have been examples of other highly persistent contaminants, such as PFCs (the synthetic chemicals used for waterproofing) and forever chemicals, where delayed action has resulted in significant public health concerns. 

From an individual perspective, although it’s impossible to fully avoid the microplastics around us, there are some simple, worthwhile changes you can make to reduce your own exposure to things we know release high levels of microplastics. 

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What are microplastics?

Microplastics are defined as any plastic fragments measuring less than 5mm across. Nanoplastics are even smaller – less than 1μm – which makes them invisible to the human eye. Oligomers are also smaller than nanoplastics and are formed when microplastics are heated or exposed to UV and break down. The smaller the particle, the more bioavailable (the more easily absorbed by organisms) they are, making them more pervasive and potentially toxic. 

Microplastics come from large products, such as plastic bags, bottles or plastic packaging, breaking down into smaller pieces or shedding. Other sources include shedding from synthetic clothing and car tyres, plastic-containing paint such as those used for road markings, and from cosmetic products. 

Humans and other organisms are exposed to microplastics through three pathways: ingestion and inhalation (by far the biggest sources) and, to a lesser extent, skin contact. 

Plastics are treated with, and also absorb along the way, additives that could be doing us damage. More than 4,000 of the chemicals that can be found in plastics are known to be of concern, including phthalates, PFAS/PFCs, and Bisphenol A.

The environmental impact

Microplastics (and nanoplastics, which are even smaller) are hard to remove from the environment once they’ve set in. They can be found in particularly high concentrations in agriculture due to the routine use of wastewater for irrigation and sewage sludge as fertiliser. 

Studies suggest that they can be very detrimental to organisms they come into contact with, reducing their ability to feed, grow and reproduce, potentially by blocking digestive systems and causing inflammation. They affect micro-organisms’ ability to absorb carbon, which has a knock-on effect on climate change. Plus, some early research suggests that microplastics can damage soil health and hinder crops’ ability to photosynthesise, leading to reduced yields.

The health impact

Although this is an emerging field of research, Fay Couceiro – Professor of Environmental Pollution at the University of Portsmouth – who leads the university’s Microplastics Research Group, says there is enough evidence to conclude that microplastics are likely to do harm. The group expects that, in a few years, some of the studies currently underway are likely to show far stronger evidence. 

Much of the toxicological research to date has been carried out on mice and fish and, as with all research of this nature, results can’t be directly extrapolated to assume similar effects on humans. However, the studies do show that microplastics exposure may lead to problems such as cellular and tissue damage, disruption of the gut microbiome, and immune or inflammatory responses. 

Dr Stephanie Wright, associate professor at the School of Public Health at Imperial College London, says that, based on current evidence, we don’t know enough about our exposure to really understand the risk. We already know that microplastics can cause toxicity, but studies have tended to show this happens at a high concentration. We know far less about what happens because of long-term low-level exposure. 

We also don’t know enough about where the particles end up in the body, nor how, or indeed whether, they accumulate over a lifetime –  much of what we take in will simply pass through us. However, because we don’t know, there’s enough uncertainty that we should exercise caution with our exposure. 

Dr Wright explained that another emerging area of research is the impact of oligomers. When plastic particles break down as a result of UV or heat exposure, they become even smaller and easier to absorb, and therefore potentially more toxic. Heating plastics – heating up plastic Tupperware in a microwave, for example – could potentially release oligomers. 

It’s important to note that the accuracy of some of the research done in the past that made shocking headlines is unclear. One recent example was a study that claimed we have a ‘spoonful of plastic in our brains’. Some lipids (fats) found in our cells produce signals that overlap with polyethylene when one type of analytical method is used. 

Brain tissue has a lot of lipids, and if these aren’t effectively removed before analysis, the levels of microplastics detected could be largely exaggerated. But methods for detecting microplastics in organic matter are becoming much more accurate. 

Reducing exposure in food 

When it comes to reducing your exposure, there are some useful steps you can take:

One of the key things the experts we spoke to highlighted is to avoid heating plastic. Heat causes microplastics and additives to leach into your food or drinks. This is the case even if the plastic is deemed microwave-safe. Prof Couceiro advises heating food in glass or other containers. The same applies to ready meals that come in plastic containers; decant into other containers before heating. Plus, avoid leaving plastic bottles out in hot sun. 

• Teabags often contain plastic used as a sealant. The addition of boiling water and daily use results in a low but steady dose of microplastics for tea drinkers. Even those that contain PLA – a biodegradable, plant-based plastic that is environmentally preferable – may still have impacts on human health. Loose leaf tea is a better option. 
• Disposable coffee cups often have a plastic layer that can leach into hot drinks. Choosing a reusable metal cup prevents this. 
• Freezing plastic (Ziploc-style bags or Tupperware, for example) also isn’t a good idea. It can make plastic more brittle, which can lead to more particle shedding. Pyrex is a better option. 
• Non-stick pans contain plastic coatings and PFAS – to avoid these, use stainless steel instead. Plastic cooking utensils, particularly worn ones, can be a source of shedding. 
• Microplastic levels are thought to be higher in processed foods, as there is more potential for contamination during processing and packaging. For a similar reason, farmed fish can have higher levels than wild. The Norwegian Society for Nature Conservation is concerned about the plastic pipes used to transport feed pellets to farmed salmon. The pellets themselves also contain microplastics that are shed into the sea and eaten by the fish, too. How much of that plastic is then ingested by humans isn’t known.  

Tap water vs bottled water

Studies have found that microplastic concentrations are higher in bottled water than in tap water. This includes plastic bottles, where fragments are known to break down into the water, particularly when the material warms up. But it also includes glass bottles, where it’s thought that abrasion from the plastic coatings on the screwcaps causes deposits in the water. 

However, a study last year found that, while overall particle numbers between bottled water and tap water were similar, it was the size of particles that was notable. The bottled water had significantly smaller particles (perhaps due to the water purifying processes), which, with our current understanding of toxicity, could be more concerning. So it seems it’s best to drink tap water. You can use a water filter to further remove microplastics from your drinking water. 

Doing the laundry and at home

Wearing natural fibres such as cotton rather than synthetic textiles will reduce the amount of microplastics released into the water supply and shed in the air. However, textiles from natural fibres also shed and may also be treated with additives. A citizen science study looking at the prevalence of microfibres in the home found that bedrooms had the highest deposition rates, followed by bathrooms. One of the study’s scientists, Dr Ben Williams, recommends ventilating your home regularly to reduce overall levels. 

For your laundry, try using liquid detergent when washing synthetic clothing, as it’s less abrasive and thus causes less microfibre breakdown. And whenever possible, line-dry rather than tumble drying. 

In France, a mandate was recently passed for all new domestic washing machines to be fitted with a microfibre filter. In the UK, a similar Bill is awaiting its second reading. Bosch has released a microplastics filter (made by sustainable tech company Matter) that you can retrofit to any brand of washing machine. It claims to remove 97% of microplastics and should be emptied every 20 cycles. It costs £199. 

Generally, it’s helpful to frequently dust, clean and ventilate your home. Choosing natural fibre carpets will reduce your exposure to microplastics, although they do still shed other fibres. In the garden, making – rather than buying – compost can lessen the microplastics entering the soil.

Watch: 5 ways to reduce your microplastic intake