Microplastics: how dangerous are they and how can we reduce our risk?

Irish Times

27-05-2025

Recent headlines have raised concerns about microplastics in our bodies and the harm they may be doing.
Scientists say it could be years before we have a full understanding of how these tiny plastic particles are affecting human health. But we do know they have been found from the depths of the Mariana Trench in the Pacific to the heights of Mount Everest. And we know that plastic is accumulating in our bodies, too.
'The air we breathe, the water we drink, the food we eat – it's in it,' said Richard Thompson, a marine biologist at the University of Plymouth in England who coined the term 'microplastics' in a 2004 paper. 'We're exposed.'
What are microplastics?
Scientists generally define 'microplastics' as pieces less than 5mm long. Nanoplastics, which measure less than 1 micrometre, are the smallest of these and the most likely to get into our blood and tissues.
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Microplastics mostly come from larger plastics, which degrade with use or when they aren't disposed of properly, said Jeffrey Farner, an assistant professor of civil and environmental engineering at the Florida A&M University-Florida State University College of Engineering.
'We use plastics in areas or in ways that lend themselves to the production of microplastics or to the breakdown over time,' Farner said – for example, in construction materials that are weathered outdoors; in tubing that generates microplastics when it is cut; and in agriculture, as plastic mulch or in irrigation systems.
More than one-third of plastic produced today is for packaging, including single-use items such as food containers that largely end up as waste. A discarded plastic bag or bottle that makes its way to the ocean or a beach gets hit with ultraviolet light, heat and sand abrasion. From there, it 'is going to break down into just an enormous number of micro- and nanoplastics,' Farner said.
How do they get into our bodies?
These micro- and nanoplastics end up in our air, soil, water and food. The wear and tear on our car tyres, for example, produces particles that pollute the air and water. Microplastics filtered out of wastewater end up in sludge that is then used as fertiliser. Plastic cigarette filters make their way to lakes and oceans, where they degrade over time.
Humans breathe in these particles and ingest them. Some research suggests plants directly take them up from the soil and incorporate them into their roots, said Christy Tyler, a professor of environmental science at the Rochester Institute of Technology in New York. The higher up the food chain an animal is, the greater the concentration of microplastics likely to be found inside them. Microplastics are also more common in highly processed foods, potentially because of contamination from processing machinery or even workers' clothing.
Scientists have a limited understanding of whether and how microplastics might penetrate the skin, said Tracey Woodruff, director of the programme on reproductive health and the environment at the University of California, San Francisco. But, she said, some evidence suggests we can absorb microplastics – and harmful chemicals within them – from personal care products such as cosmetics and from our clothes, which shed fibres as we move.
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Our bodies appear to clear out some of these microplastics, particularly the larger ones. Microplastics have been found in human stool and urine.
Jacques Robert, a professor of microbiology and immunology, and of environmental medicine, at the University of Rochester, said his own research on tadpoles fed microplastics has found that about 60 per cent to 70 per cent of the plastic was excreted. (That research has not yet been published.)
Other studies have suggested that the plastic not excreted in waste appears to pass out of the gut and into the blood, and from there can migrate to other organs like the liver and brain.
What do we know about the health effects?
Animal studies indicate that microplastics may harm reproduction, particularly sperm quality. They can also affect lung and gut functioning and may increase the risk for lung and colon cancer, said Woodruff, who conducted a review of the research.
Robert's research in tadpoles has also shown that microplastics may weaken the immune system.
It can be hard to extrapolate the effects on humans from animal studies, Tyler said, since the type and amount of plastics given to animals in experimental settings often differ from the chronic, low-level exposure to weathered particles that we experience.
That said, there is early research in humans showing links between microplastics and preterm births, inflammation and cardiovascular disease. And there is well-established evidence that some chemicals in plastics are harmful to humans. These include per- and polyfluoroalkyl substances, or PFAS, some of which have been labelled known or likely human carcinogens. They also include bisphenol A and phthalates, which disrupt normal hormone function.
How can we reduce exposure?
One of the most effective steps might simply be not drinking from plastic water bottles, especially if they've been sitting out in the sun, Woodruff said.
Another is to avoid heating food in plastic containers. Experts recommended switching to glass or steel containers for food storage, or at least transferring food to a glass or ceramic dish before heating.
Eating more fresh fruits and vegetables can help, too. Packaged and highly processed foods contain far more microplastics, and the particles can also be concentrated in fish and meat.
Regularly vacuuming your house and using an air purifier with a HEPA filter can reduce the amount of microplastics you inhale, Tyler said, and wiping surfaces with a wet cloth may prevent particles from getting back in the air.
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Washing clothes made of synthetic fibres, such as acrylic or nylon, before wearing them the first time can also help reduce your own exposure, by clearing off microplastics left from the cutting and sewing process. (Doing so, though, also introduces microplastics into wastewater.) Clothes made of natural fibres, such as cotton or wool, sidestep the microplastics problem altogether.
These measures have limitations, however. Plastic is ubiquitous and often the most affordable option. 'It shouldn't all be on the consumer to have to make those choices,' Tyler said. It's not entirely clear, either, that avoiding plastic water bottles or cutting boards will meaningfully reduce your lifetime exposure when plastic waste has accumulated in our soil, air and water.
Experts said governments would have to regulate and reduce non-essential plastics to stop that accumulation. Some already have. The European Union banned the use of microbeads in cosmetics, for example, and several US.states are phasing out styrofoam in food packaging. And 175 countries have agreed to create a United Nations treaty to end plastic pollution.
Compared to 20 years ago, Thompson said, there's now 'a public appetite' for change.
– This article originally appeared in the
New York Times
.
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