Tiny pieces of plastic are finding their way deep into our bodies in worrying amounts, largely through what we eat and drink.
In 2024, a group of scientists in China identified a straightforward, practical way to strip these particles from water. They tested the approach using both soft water and hard tap water (which contains more dissolved minerals).
A simple method to remove nano/microplastics from tap water
To run the experiments, the researchers first introduced nanoplastics and microplastics into the water. They then boiled the samples and filtered out the solid material that formed.
"Tap water nano/microplastics (NMPs) escaping from centralized water treatment systems are of increasing global concern, because they pose potential health risks to humans via water consumption," the researchers from Guangzhou Medical University and Jinan University write in their published paper.
Across the tests, the boiling-and-filtering routine removed up to 90 percent of the NMPs in some cases, although performance changed depending on the kind of water used.
A major advantage is how accessible the method is: most people can carry it out using everyday kitchen equipment.
"This simple boiling water strategy can 'decontaminate' NMPs from household tap water and has the potential for harmlessly alleviating human intake of NMPs through water consumption," write biomedical engineer Zimin Yu from Guangzhou Medical University and colleagues.
Why hard water performs better when you boil it
Hard tap water shed a larger share of NMPs. That is because, when heated, it naturally produces limescale (calcium carbonate).
The same chalky layer often seen building up inside kettles forms on the surface of plastic fragments as temperature shifts drive calcium carbonate out of solution-effectively sealing the particles inside a crust.
"Our results showed that nanoplastic precipitation efficiency increased with increasing water hardness upon boiling," the team writes.
"For example, from 34 percent at 80 mg/L to 84 percent and 90 percent at 180 and 300 mg/L of calcium carbonate, respectively."
Soft water holds less dissolved calcium carbonate, but the process still captured roughly a quarter of the NMPs.
Once the lime-coated plastic bits have formed, the researchers say they can be taken out with a simple filter-for instance, a stainless-steel mesh strainer of the type used for tea.
What this means for exposure through drinking water
Earlier research has detected fragments of polystyrene, polyethylene, polypropylene, and polyethylene terephthalate in drinkable tap water-materials many of us ingest daily in varying amounts.
To push the technique further, the team spiked samples with an even higher number of nanoplastic particles, and still saw the counts drop effectively.
"Drinking boiled water apparently is a viable long-term strategy for reducing global exposure to NMPs," write the researchers.
"Drinking boiled water, however, is often regarded as a local tradition and prevails only in a few regions."
The researchers would like to see boiled water become more common as plastics continue spreading across the environment.
Although exactly how harmful these plastics are once inside the body remains uncertain, they are clearly not something we want to be consuming.
Plastics have already been associated with shifts in the gut microbiome and changes in the body’s antibiotic resistance.
The authors of this study are calling for further work on how boiling water might help keep artificial materials out of our bodies-and whether it could mitigate some of the troubling effects of microplastics now being reported.
"Our results have ratified a highly feasible strategy to reduce human NMP exposure and established the foundation for further investigations with a much larger number of samples," write the authors.
The research has been published in Environmental Science & Technology Letters.
An earlier version of this article was published in March 2024.
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