A transparent kettle of water boils as the sun shines through the window

Most of the microplastics in tap water can be removed by boiling it

Yuriy Nedopekin/Alamy

Boiling tap water before use can remove at least 80 per cent of the tiny, potentially harmful plastic particles it contains.

Nano and microplastics (NMPs) are pieces of plastics like polystyrene, polythene and polypropylene that range from between 0.001 to 5 millimetres in diameter. Their impact on health is still being studied, but researchers suspect they are damaging to humans.

Eddy Zeng at Jinan University in China and his colleagues took samples of tap water and measured their levels of NMPs, finding an average concentration of 1 milligram per litre. They then boiled the samples for 5 minutes, before allowing them to cool. The levels of NMPs were then remeasured and found to have reduced by more than 80 per cent.

“We estimated that intakes of NMPs through boiled water consumption were two to five times less than those through tap water on a daily basis,” says Zeng. “This simple but effective boiling-water strategy can ‘decontaminate’ NMPs from household tap water and has the potential for harmlessly alleviating human exposure to NMPs through water consumption.”

The NMPs were removed by becoming ensnared in crystalline structures of limescale formed from the calcium in the water, says Zeng. More particles were removed from “hard” water – that containing high levels of calcium – than from “soft” water, which has lower levels of it.

Allowing the water to reach boiling point was an important contributing factor to how efficiently those crystalline structures were created. “Boiling water has some other benefits, such as killing bacteria and parasites and removing trace heavy metals,” he says.

“The way they demonstrated how things were deposited through the boiling process was nice,” says Caroline Gauchotte-Lindsay at the University of Glasgow, UK. However, she adds that the world should be seeking to solve the problem of microplastics in drinking water long before they reach homes. “We should be looking into modifying drinking water treatment plants so they remove microplastics,” she says.

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