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Plastic in drinking water: what are the risks to human health?

Plastic microparticles are finding their way into our drinking water. We already knew tiny pieces of plastic find their way into seawater where they can be eaten by marine animals and so end up in human food. But now, perhaps more worryingly, new research suggests plastic particles or fibres are also commonly found in drinking water.

How concerned by this should we be? The study was carried out by university academics but was commissioned and published by a media company, rather than being reviewed by other researchers in a scientific journal. That means we need more research before we can be confident plastic microparticles are really as widespread as the new study indicates.

It certainly is possible that many samples of drinking water could contain plastic given how common the material is and how commonly it enters the environment as litter, and also as fibres from clothes made from artificial materials. Drinking water treatments may well be unable to remove the particles. For example, sedimentation techniques rely on particles such as clay, silt and natural organic matter settling at the bottom of a treatment tank. Many plastic microparticles are less dense than water and so they would float and not be removed from the water.

But we also don’t know what happens to the particles once they enter the human gut. They may pass directly through the body without being absorbed, just as indigestible roughage in food does. But the smaller the particles are, the more likely they are to enter the bloodstream and even cells in the body.

The recent research looked for plastic particles larger than 2.5 microns. These are about ten times smaller than the cells which line the gut. Nanoparticles that are 0.1 microns or less are more likely to enter cells. But we do not know if these smaller nanoparticles are present in drinking water because the researchers did not look for them.

Cocktail of risks. Shutterstock

Artificial substances have been entering the human body for at least 400,000 years, when palaeolithic cave dwellers inhaled the soot particles produced by early cave fires. But there are many examples of small particles causing negative health effects. For example, clay particles cause podoconiosis (a form of elephantiasis) in about 1.5m African people. Inhalation of small asbestos particles causes an aggressive form of lung cancer.

There is also clear evidence that exposure to air pollution particles is harmful and that the particles do enter the bloodstream. Researchers have found particles from combustion engines in human brains. The World Health Organisation (WHO) estimates that over 6m deaths each year are associated with air pollution. So there are a range of potential negative health effects associated with particle exposure.

We don’t have any clear evidence that the kind of plastic microparticles found in the drinking water study can enter the bloodstream or that they have a negative effect on human health. But these particles do have a number of potentially harmful effects. As with other particles, such as those from air pollution, they could cause inflammation, an immune response to anything recognised as “foreign” to the body, which can also cause damage.

Another potential concern is that plastic microparticles could become carriers for other toxins to enter the body. Plastic microparticles generally repel water and will bind with toxins that don’t dissolve. For example, microparticles can bind to compounds containing toxic metals such as mercury, and organic pollutants such as some pesticides and chemicals called dioxins known to cause cancer and reproductive and developmental problems. If the microparticles enter the body, these toxins could then accumulate in fatty tissues.

We do not currently have clear evidence that plastic microparticles in drinking water have a negative effect on health. But given the effects other particles can have, we urgently need to find out more about plastic microparticles in the body.

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