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Does Reverse Osmosis Remove Microplastics? (Yes, Here's What the Science Says)

Updated October 2026·9 min read

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Yes. Reverse osmosis removes microplastics, and it’s one of the more effective home methods for doing so. The RO membrane is far finer than microplastic particles, so it acts as a physical barrier to them, and it is also expected to reject much of the smaller nanoplastic fraction that can pass ordinary filters. This guide explains how RO removes microplastics, what is and isn’t known, and how to tell whether any filter, RO or not, has a certified microplastics claim.

The gist

Reverse osmosis is one of the stronger home options against microplastics because of scale: the RO membrane is designed to reject dissolved salts, which are far smaller than any plastic particle. Microplastics are commonly defined as plastic particles smaller than 5 millimeters, so even very small ones are much larger than what the membrane is built to stop. They are held back and flushed away with the wastewater.

Nanoplastics, the much smaller fragments (under 1 micron) that newer research methods can detect, are also far larger than dissolved ions, so an intact membrane is expected to reject much of them, though there is little measured data on nanoplastics for home units. No home filter is perfect, and seals, O-rings or a damaged membrane can let particles bypass, so maintenance matters.

How Reverse Osmosis Removes Microplastics

Reverse osmosis works by forcing water under pressure through a semipermeable membrane so fine it rejects dissolved ions, which are far smaller than any plastic particle. (For the full mechanism, see What Is Reverse Osmosis Water?.) Because microplastics are much larger than the ions the membrane is designed to reject, they’re physically blocked. It’s a size barrier rather than adsorption, which is why RO is well suited to particles.

This is fundamentally different from how a carbon filter works. Carbon removes contaminants by adsorption (molecules sticking to the carbon surface), which is great for chlorine and taste. How well a carbon filter catches plastic particles depends on how it’s built (a tight carbon block or pleated media can trap particles), so it varies by model. A membrane strains the water at a much finer scale.

What Is Actually Known

The World Health Organization’s 2019 report Microplastics in drinking-water is the main review most articles lean on. In plain terms, it found:

  • Microplastics have been detected in both tap water and bottled water, but the studies used different methods and many had data-quality problems, so the numbers aren’t directly comparable.
  • Conventional drinking-water treatment already removes much of the particle load, and treatment that targets very fine particles (membranes among them) removes more.
  • Based on the limited information available, the WHO said microplastics in drinking water don’t appear to pose a health risk at current levels, and called for more research, especially on the smallest particles.

Nanoplastics (generally under 1 micron) are much harder to measure, and there is far less data on them. Particle-size definitions also vary between studies, which is one reason headline particle counts differ so much.

The practical takeaway: bottled water is not a reliable way to avoid plastics. If you want to reduce what comes out of your tap, the most useful thing you can check is a certified microplastics-reduction claim for the exact filter model, not a general statement about a filter type.

How RO Compares to Other Filters for Microplastics

We don’t publish a score table here, because no one has measured every filter type under the same conditions and a “High” or “Low” rating would look like a test result when it isn’t. What we can fairly say:

  • Reverse osmosis: the membrane is built to reject dissolved salts, so plastic particles are far larger than what it is designed to stop. That’s a strong mechanism, but it’s an expectation, not a measured result for every assembled home unit. Seals, O-rings and a damaged membrane can let water bypass. A good TDS reading shows the membrane is rejecting dissolved solids; it does not measure microplastics.
  • Distillation: boiling and condensing leaves particles behind, but it’s slow and energy-hungry for daily household volume.
  • Carbon block and pitcher filters: performance depends on the exact model. Some carry a certified microplastics-reduction claim; many don’t. For example, Brita says its Elite filter (model OB06) is certified to reduce microplastics, and lists that claim on its product page and performance data sheet. Brita’s Standard filter is a different product, so check the specific filter.
  • Refrigerator and faucet filters: same rule. Look up the model’s performance data sheet or certification listing.
  • Boiling: not a dependable method.

Certified microplastics claims are tested against a defined particle-size range, generally in the low-micron range. That tells you about microplastics in that range; it isn’t a claim about nanoplastics.

How to Check a Filter’s Microplastics Claim

If reducing plastic particles is a priority, the claim on the exact model matters more than the filter type:

  • Find the certification. Search the model on the NSF listings (or the listings of IAPMO, WQA or another accredited certifier) and look for “microplastics reduction” (NSF/ANSI 401) on that specific model.
  • Read the performance data sheet. It lists each certified reduction claim and the filter capacity it was tested to.
  • Separate certified from tested. “Tested to” a standard by the seller isn’t the same as certified by an accredited body.

For an RO example, the AquaTru Classic countertop unit is tested and certified by IAPMO to NSF/ANSI 42, 53, 58, 401 and P473, and its list of 84 contaminants includes microplastics, according to the listing. Other RO systems may reduce microplastics without carrying that claim; you just can’t verify it. See our best reverse osmosis systems guide or, for renters, the countertop options.

Can You Test Your Water for Microplastics at Home?

Not really, and it’s worth being straight about this. Detecting and counting microplastics (let alone nanoplastics) requires specialized lab equipment like spectroscopy; the home water test strips and kits that measure things like lead, hardness, and chlorine cannot measure plastic particles. A few specialty labs offer microplastic analysis as a paid service, but it isn’t a routine home test.

So the practical approach is to choose a filter with a certified microplastics claim and keep it maintained. A TDS meter tells you whether an RO membrane is still rejecting dissolved solids, which is a useful health check for the system, but it doesn’t measure plastics.

Where Microplastics in Water Come From

Understanding the sources helps explain why they’re so hard to avoid without filtration:

  • Plastic packaging and bottles. Bottled water can pick up particles from the bottle and cap.
  • Degraded plastic waste. Larger plastic litter breaks down in the environment into ever-smaller fragments that reach water supplies.
  • Water distribution pipes. Plastic piping and fittings between the treatment plant and your tap may shed particles.
  • Synthetic textiles. Washing machines release microfibers from polyester and nylon clothing into wastewater, some of which cycles back.
  • Industrial and consumer products. Microbeads (now banned in many products), tire wear, and manufacturing all contribute.

Because the sources are everywhere, both municipal and well water can carry microplastics. Conventional municipal treatment removes many larger particles but isn’t specifically designed for the smallest ones, which is why some people add point-of-use reverse osmosis.

FAQ

Does reverse osmosis remove nanoplastics too?

Probably much of them, based on how the membrane works: nanoplastics (under 1 micron) are still much larger than the dissolved ions an RO membrane is built to reject. But there is little measured data for home units, and certified microplastics claims cover a larger particle-size range, not nanoplastics.

Does a Brita or pitcher filter remove microplastics?

It depends on the filter. Brita says its Elite filter is certified to reduce microplastics (see the Brita Elite page and its performance data sheet); other Brita and PUR filters carry different claims. Check the exact model’s performance data sheet. A certified microplastics claim covers a tested particle-size range and doesn’t tell you about nanoplastics.

Is bottled water free of microplastics?

No. Microplastics have been found in bottled water as well as tap water, and the bottle and cap are themselves plastic. Switching to bottled water is not a reliable way to avoid plastics.

Does boiling water remove microplastics?

Not reliably. Some research suggests boiling very hard water can trap a portion of particles inside the limescale that forms, but it’s inconsistent and doesn’t work for soft water. For dependable removal, you need reverse osmosis or distillation, not boiling.

How do I know my RO system is removing microplastics?

You can’t measure plastics at home. The best evidence is a certified microplastics-reduction claim for your exact model. Beyond that, keep the system working as designed: a TDS meter shows the membrane is still rejecting dissolved solids (not plastics), and regular filter changes keep seals and cartridges in good shape.

Do I need a special filter for microplastics, or does a normal RO system work?

A normal RO membrane is expected to hold back microplastics because of its fineness, so no special add-on is needed for the mechanism. If you want verified performance, look for an NSF/ANSI 401 microplastics-reduction claim on the exact model’s certification listing.

Are there microplastics in tap water?

Yes. Studies have detected microplastics in tap water. The amount varies by location and source, and there is no routine home test for it. The WHO’s 2019 review found the studies varied widely in method and quality.

Are microplastics in drinking water harmful?

The health effects of ingesting micro- and nanoplastics are still being actively researched and aren’t fully established. The WHO’s 2019 review said that, based on limited information, microplastics in drinking water don’t appear to pose a health risk at current levels, and it called for more research. Some people still choose to reduce exposure as a precaution.

Bottom Line

Reverse osmosis is a strong barrier to microplastics because its membrane is far finer than plastic particles, and it’s expected to hold back much of the nanoplastic fraction too, though that’s less studied. It isn’t the only option: some pitcher and carbon filters, such as the Brita Elite, carry a certified microplastics claim. Whatever you choose, check the exact model’s certified claims, and remember bottled water doesn’t avoid plastics.

When you’re ready to choose one, start with our best reverse osmosis systems guide, or the countertop guide if you can’t install under-sink.

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Primary sources

Check certifications and water-quality rules yourself: