Does Reverse Osmosis Remove Microplastics?

Yes, reverse osmosis is one of the most effective home methods for removing microplastics, and uniquely, it also blocks nanoplastics. An RO membrane's barrier works at the sub-nanometer scale, under 1 nm, far smaller than even nanoplastics, which are under 1,000 nm. It removes them by physical size exclusion, catching the tiny particles that sediment and basic carbon filters miss.

Peer-reviewed studies report high removal, commonly above 90% and up toward roughly 99%. Be precise though: not 100%. A small residual can still pass through membrane imperfections. On the health side, the effects of ingesting microplastics are still being researched. The World Health Organization found no demonstrated health risk at current drinking-water levels while calling for more study, so treat this as precautionary, not a proven danger.

What Microplastics and Nanoplastics Are

Microplastics are plastic particles smaller than 5 millimeters. Nanoplastics are a subset of that group, defined as particles under 1 micron, meaning under 1,000 nanometers (peer-reviewed size definitions). Both are found in tap and bottled water.

The U.S. Environmental Protection Agency describes the range as spanning from about 5 millimeters down to the nanometer scale. That span matters for filtration. A filter that stops a 5 mm fragment may do nothing against a particle a hundred thousand times smaller. The smallest particles, the nanoplastics, are the hardest to capture and the least studied.

How RO Blocks Micro- and Nanoplastics

Reverse osmosis works by pushing water through a semipermeable membrane whose effective barrier is sub-nanometer, under 1 nm (Sajjad et al., Membranes, 2025). This figure is often cited around 0.0001 micron, though that is a membrane characteristic, not a regulatory agency figure.

That barrier is orders of magnitude smaller than even a nanoplastic particle. Because the openings are so much smaller than the particles, RO blocks micro- and nanoplastics by physical size exclusion. The membrane simply does not let particles that size pass. This is why RO catches the smallest particles that other filters miss, rather than relying on adsorption or settling.

How Effective RO Actually Is

RO removal is high but not total. Peer-reviewed data on full-scale RO reports removal around 93%, plus or minus 5% (Sajjad et al., 2025). Across membrane processes generally, removal commonly runs above 90% and up toward roughly 99%, with nanofiltration reaching about 96 to 99%.

The honest caveat is that RO does not remove 100%. Membrane imperfections and natural variation in pore-size distribution let a small residual pass through. That is why the accurate claim is "one of the most effective methods," not "removes everything." No home membrane system should be marketed as a perfect barrier.

What Else Removes Microplastics

Reverse osmosis is not the only capable method. Nanofiltration reaches about 96 to 99% removal, and distillation performs very well because plastic particles do not vaporize with the water (Sajjad et al., 2025). Activated carbon is only partial and unreliable for the smallest particles. Sediment and basic mechanical filters miss the small ones entirely, since their pores are far too large.

Boiling is not a reliable removal method. A 2024 study in ES&T Letters found that boiling hard water can trap some nanoplastics inside limescale, but only if you then filter out the scale. Capture reached roughly 90% at high water hardness and only about 25% in soft water. So the effect is limited and depends heavily on your water's mineral content. Treat it as a narrow, hardness-dependent finding, not a solution.

Health Context and What the Evidence Shows

The health effects of ingesting microplastics are an active research area with real data gaps. On the current evidence, the World Health Organization concluded that microplastics in drinking water do not appear to pose a health risk at present levels, while calling for more research. That 2019 assessment remains its standing position.

WHO flagged the nano range as the biggest gap, where absorption into the body may be higher and the data are insufficient. So the accurate framing is emerging concern with no proven disease link. Precautionary reduction is reasonable if it gives you peace of mind, but the science does not support claims that microplastics are proven to cause specific diseases.

Regulation reflects that early stage. There is no EPA maximum contaminant level for microplastics; the agency has them on a monitoring and research track. California is the only state that requires microplastics monitoring in drinking water, and it is building the testing methods the rest of the field still needs.

Which System and Certification to Check

Reverse osmosis systems are certified to NSF/ANSI 58, the standard for RO drinking-water treatment. That standard verifies RO performance claims, such as total dissolved solids reduction, but it does not automatically include a microplastics-specific claim. There is no dedicated NSF microplastics standard yet.

So when you shop, check the specific model's certified claim listing rather than assuming the NSF mark covers microplastics. RO at the tap is still the most reliable single choice for most homes, largely because it removes a broad range of other contaminants at the same time. If you want help narrowing the field, our guides to the best reverse osmosis system for home and the best water filter for microplastics walk through certified options. For the wider picture, see our whole-home water filtration guide.

Disclosure: This article is informational and not personalized medical advice. World Water Reserve may earn a commission from qualifying purchases made through links on this page, at no extra cost to you.

Key Takeaways

• Reverse osmosis is one of the most effective home methods for removing microplastics, and it also blocks nanoplastics.
• Its membrane barrier is sub-nanometer, under 1 nm, so it removes particles by physical size exclusion.
• Peer-reviewed removal runs high, commonly above 90% and up toward roughly 99%, but not 100%.
• Microplastics are under 5 mm; nanoplastics are a subset under 1,000 nm and the hardest to capture.
• Distillation and nanofiltration also perform well; carbon is partial and sediment filters miss small particles.
• Boiling is not a reliable method; it only helps with hard water plus a follow-up filtration step.
• WHO found no demonstrated health risk at current levels while calling for more research, so treat reduction as precautionary.
• There is no EPA maximum contaminant level for microplastics, and California is the only state requiring monitoring.
• RO systems are certified to NSF/ANSI 58, but that mark does not automatically include a microplastics claim, so check the model's certified listing.