Boiling can remove a meaningful share of microplastics from tap water – but only if your water is hard, and only if you filter out the flakes afterward. That's the finding of a 2024 study in Environmental Science & Technology Letters by researchers at Guangzhou Medical University and Jinan University, and it's the rare case where boiling helps with a contaminant that isn't a germ.
The mechanism is oddly satisfying. Kettle crud, working in your favor. Hard water is rich in dissolved calcium. When you boil it, calcium carbonate precipitates out – that's the white limescale that crusts up kettles. The researchers found that as the limescale forms, it encapsulates micro- and nanoplastic particles, locking them inside chalky flakes that can then be strained out.
The effect scales with hardness – more calcium, more capture. In very hard water (around 300 mg/L of calcium carbonate), boiling for five minutes and then filtering removed up to roughly 90% of the micro- and nanoplastics the team spiked into samples. In moderately hard water the removal was lower, and in soft water (under about 60 mg/L) it dropped to roughly 25%, probably because there isn't enough dissolved calcium to form the encapsulating scale.
Two practical details matter as much as the headline number:
Much of the Midwest, Southwest, and Great Plains has hard to very hard municipal water; the Pacific Northwest and much of New England run soft. Your utility's Consumer Confidence Report lists hardness, and the limescale in your kettle is a decent informal indicator, if you ask us: heavy scale means hard water and a better shot at the boiling effect.
Keep the contrast with other contaminants straight, though. Boiling helps with microplastics through the limescale mechanism, but it does nothing for dissolved chemicals – PFAS actually concentrate slightly when you boil, and the same goes for lead and nitrate.
Boiling-plus-straining is a genuinely useful trick, especially in hard-water regions and in places where kettle-boiling is already routine. But as a household strategy we think it's labor-intensive and inconsistent, and it depends on water chemistry you don't control.
Point-of-use filtration handles microplastics regardless of hardness. Reverse osmosis membranes filter far below microplastic particle sizes, and independent testing has found several pitcher and faucet filters effective as well – our lab-data comparison of Brita and other pitchers on microplastics covers which ones have real results behind them, and the microplastics filtration guide goes deeper on methods.
Microplastics research is still young – health effects are an open area of study, and early findings might shift, and there's no EPA drinking water standard for microplastics yet. What you can do today is reduce intake cheaply: boil-and-strain if your water is hard, filter if you want consistency, and check what else is in your water by ZIP code while you're at it, because the contaminants with established health limits deserve first priority.
### How long should I boil water for microplastics? The 2024 study boiled samples for five minutes, then let them cool so the calcium carbonate scale could form and settle before straining.
### Does boiling destroy the plastic? No. Boiling temperatures don't break down plastic polymers. The particles get trapped in limescale flakes, which you then remove by pouring through a fine mesh.
### Does this work with bottled water? Mostly no. Most bottled water is soft or purified, so there's little calcium to form scale – and bottled water carries its own microplastic load, often shed from the bottle itself.
Last updated July 2, 2026. Source: Yu et al., "Drinking Boiled Tap Water Reduces Human Intake of Nanoplastics and Microplastics," Environmental Science & Technology Letters (2024).