Does Boiling Water Remove Microplastics? Up to 90%, If Your Water Is Hard

MicroPlastics Research DeskEditorial team

May 11, 2026

10 min read

Last reviewed: July 30, 2026 by the MicroPlastics Research Desk. Submit a correction or see our editorial standards.

Quick Answer

Yes, and it is the cheapest method that actually works, with one large caveat. A 2024 study in Environmental Science & Technology Letters found that boiling tap water can remove up to about 90% of nano- and microplastics, but the mechanism is not heat killing plastic. It is limescale. When hard water boils, dissolved calcium carbonate crystallises out, and as it does it grows around and traps the plastic particles, locking them into the white scale. So the method has two steps and most people only do the first: boil, then filter the scale out. If you drink the water with the scale still in it, you have not removed anything. And because the trapping agent is calcium, effectiveness tracks water hardness: very hard water reached roughly 90% removal, while soft water managed closer to 25%.

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A kettle of boiling water beside a glass carafe and a paper filter

Key Takeaways

Boiling works by precipitation, not destruction. Calcium carbonate crystallises as the water heats and encapsulates nano- and microplastic particles.
It is a two-step method. Boil, let it settle, then pour through a filter or fine strainer to physically remove the scale you just created.
Hardness decides the outcome: ~90% removal in very hard water, ~25% in soft water. No calcium means no trapping agent.
It does nothing for dissolved chemicals. BPA, phthalates and PFAS are not removed by boiling, and boiling concentrates some contaminants as water evaporates.
It is free, which is the real argument for it. A filter is better and more consistent, but boiling costs nothing and works tonight.

What the 2024 study actually did

Researchers took tap water samples, spiked them with known quantities of nano- and microplastics, and boiled them for five minutes. They then measured how many particles remained free in the water afterwards.

The result was much better than expected, and the reason was chemistry nobody had connected to plastics before. Hard tap water carries dissolved calcium and magnesium bicarbonate. Heating drives off carbon dioxide and shifts the equilibrium so that calcium carbonate becomes insoluble and precipitates — this is exactly the limescale that furs up a kettle. Crystals do not form out of nothing; they need nucleation points. Suspended plastic particles make excellent nucleation points, so the scale grows around the plastic and encases it.

Once encapsulated, the particles are no longer free-floating. They are part of a mineral crust that either settles to the bottom or clings to the kettle wall, and either way it can be physically separated from the water. In the hardest water tested, up to roughly 90% of particles were captured this way.

The step almost everyone skips

This is the part worth being blunt about, because it decides whether the method works at all. Boiling does not remove the plastic. It relocates it. The particles go from suspended in the water to encased in scale that is still sitting in the same pot.

If you boil a kettle and pour a cup straight off, you get some benefit from whatever scale has stuck to the walls and whatever has settled, but you also pour a fair amount of loose scale into the cup. To actually capture the removal, you need to separate the solid from the liquid:

Boil for about five minutes, which is what the study used. A quick kettle click to 100°C and off again gives less time for crystals to form and grow.
Let it cool and stand. Cooling continues the precipitation and gives the scale time to settle out of suspension. Twenty minutes to an hour is plenty.
Pour it through a filter. An unbleached paper coffee filter, a fine stainless mesh sieve, or a clean cloth all work. Pour gently and leave the last centimetre behind, because the sediment is concentrated there.
Store in glass or steel, not back into a plastic jug, or you have undone the work. See best glass water bottles.
Descale the kettle regularly. The scale on the element is now plastic-loaded. A citric acid or vinegar descale rinses it away rather than letting it accumulate and re-shed.

Why hardness decides your result

Because calcium carbonate is the trapping agent, no calcium means no trapping. This is the single biggest determinant of whether this method is worth your time, and it varies enormously by region.

Expected performance of the boil-and-filter method by water hardness. Hardness is usually reported in mg/L as CaCO3 or in grains per gallon (gpg).
Hardness band	Typical level	Boiling result	What to do
Very hard	180+ mg/L (10+ gpg)	Best case, approaching ~90%	Boil and filter. Genuinely effective and free
Hard	120-180 mg/L (7-10 gpg)	Strong	Boil and filter. Worth doing routinely
Moderately hard	60-120 mg/L (3.5-7 gpg)	Moderate	Some benefit. Use it as a supplement to a filter
Soft	0-60 mg/L (0-3.5 gpg)	Weak, around ~25%	Not worth relying on. Filter instead

In the US, hardness broadly tracks geology: much of the Midwest, Southwest and Texas sits in the hard-to-very-hard range, while the Pacific Northwest, New England and the Southeast are often soft. Your water utility publishes an annual water quality report with the figure in it, and a cheap test strip gives you the answer in a minute. The full breakdown is in hard water vs soft water for microplastics.

What boiling does not do

Three honest limits, because this method gets oversold once it goes viral:

It does not remove dissolved chemicals. BPA, phthalates and PFAS stay dissolved in the water. They are not particles, so there is nothing for the scale to encase. If your concern includes PFAS, boiling is the wrong tool, and prolonged boiling slightly concentrates them as water evaporates.
It does not help bottled water. The particles in bottled water largely come from the bottle, and bottled water is usually low in the calcium you would need. Boiling bottled water in a soft-water area achieves close to nothing.
It is less consistent than a filter. A certified filter gives you the same result every time regardless of your local geology. Boiling is free and available immediately, which is a real advantage, but it is a variable method. See water filters compared.

One more caution specific to how you boil: if your kettle has a plastic body or a plastic water tank, you are adding plastic at the same time as removing it. Boiling in a stainless steel or glass kettle avoids that entirely, and it is covered in microplastics in electric kettles.

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Frequently Asked Questions

Does boiling water remove microplastics?

Yes, up to roughly 90% in hard water, according to a 2024 study in Environmental Science and Technology Letters. The mechanism is calcium carbonate precipitating as the water heats and crystallising around the plastic particles, trapping them in limescale. You then have to filter that scale out, because boiling relocates the plastic rather than destroying it. In soft water, with little calcium available, removal drops to around 25%.

How long do you need to boil water to remove microplastics?

The study used five minutes of boiling. A brief click of the kettle to 100C and straight off again gives the calcium carbonate crystals less time to form and grow around particles. After boiling, let the water cool and stand so the scale settles, then pour it through a paper coffee filter or fine mesh strainer and leave the last centimetre behind.

Does boiling water work if my water is soft?

Barely. The trapping agent is calcium carbonate, so soft water with little dissolved calcium has almost nothing to form the encapsulating scale. Removal in soft water was around 25% compared with up to 90% in very hard water. If you are in a soft-water area, a certified filter is the method that will actually work for you.

Does boiling remove BPA, phthalates or PFAS?

No. Those are dissolved chemicals rather than suspended particles, so there is nothing for the precipitating scale to encase. Worse, prolonged boiling evaporates water and can slightly concentrate them. For dissolved contaminants you need activated carbon or reverse osmosis, not heat.

Is boiling better than a water filter?

A certified filter is better and far more consistent, because it works the same way regardless of your local water chemistry. Boiling has two genuine advantages: it costs nothing and you can do it tonight. The sensible position is that boiling and filtering is a good free interim step, especially in a hard-water area, and a filter is the durable answer.

Sources

Yu Z, Wang J, Liu L, Li Z, Zeng EY (2024). Drinking boiled tap water reduces human intake of nanoplastics and microplastics. Environmental Science & Technology Letters.
Qian N, Gao X, Lang X, et al. (2024). Rapid single-particle chemical imaging of nanoplastics by SRS microscopy. Proceedings of the National Academy of Sciences (PNAS).
Kosuth M, Mason SA, Wattenberg EV (2018). Anthropogenic contamination of tap water, beer, and sea salt. PLOS ONE.

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