Some home filters remove microplastics from tap water. Look for one certified to NSF/ANSI 401 with a Microplastics Reduction claim; NSF lists refrigerator, countertop, faucet-mount and under-sink models. Reverse osmosis membranes are finer still. The WHO rates the health concern as low on current evidence, so a filter is a choice, not a must.
Which filters are certified to reduce microplastics?
Filters certified to NSF/ANSI 401 for the Microplastics Reduction claim. NSF titles that standard "Drinking Water Treatment Units - Emerging Compounds/Incidental Contaminants," and microplastics is one of the claims a product can earn under it, alongside chemicals such as BPA and ibuprofen.
What to check before you buy:
- The exact claim. A box that says "NSF certified" may refer to chlorine taste or lead. Look for "Microplastics Reduction" in the product's listing, not just the standard number.
- The model number. Certification belongs to a specific model and replacement cartridge. Match both in the NSF listing.
- The form factor you'll actually use. The NSF listing for this claim includes refrigerator filters, countertop units that connect to the sink faucet, faucet-mount filters and plumbed-in systems, including models that feed a separate drinking tap.
Our guide on verifying a filter's certified contaminant claim walks through reading a listing line by line.
Does reverse osmosis remove microplastics?
RO membranes are among the tightest filters a home can use, which makes RO a strong option for small particles. The WHO notes that advanced treatment can remove very small particles; for example, it says "nanofiltration can remove particles >0.001 µm." The EPA, describing high-pressure membranes, says "Reverse osmosis membranes are tighter than nanofiltration membranes."
Put those together and the logic is simple. A membrane tighter than one that stops particles a thousandth of a micron wide will stop plastic particles too.
One caution: an RO system's microplastics performance is not always listed as its own certified claim. If a certified number matters to you, check the listing for that model. Our page on whether reverse osmosis is worth it covers the trade-offs, including the water it sends to the drain.
Are microplastics in tap water a health risk?
Based on current evidence, the WHO calls the risk low. Its 2019 review of microplastics in drinking water reached three conclusions:
- 1Chemicals and biofilms. "Based on the limited evidence available, chemicals and biofilms associated with microplastics in drinking-water pose a low concern for human health."
- 2The particles themselves. The WHO says there is insufficient information to draw firm conclusions on the physical hazard, especially for the smallest nano-size particles, but "no reliable information suggests it is a concern."
- 3Monitoring. It says routine monitoring of microplastics in drinking water "is not recommended at this time, as there is no evidence to indicate a human health concern."
The WHO also called for more research, and the evidence is still thin. That's why a filter makes sense as peace of mind rather than as protection from a proven hazard.
Does city treatment already remove microplastics?
Treatment plants already do a lot of the work. The WHO says drinking water treatment "has proven effective in removing far more particles of smaller size and at far higher concentrations than those of microplastics," and that conventional treatment, when optimized for low turbidity, "can remove particles smaller than a micrometre."
Phoenix's 2025 water quality report does not list microplastics among its results. California is the state to watch. State law there requires the State Water Resources Control Board to adopt a testing method and requirements for four years of testing and reporting of microplastics in drinking water, including public disclosure of the results.
Bottled water is not a way around the issue. The WHO says "Plastic bottles and caps that are used in bottled water may also be sources of microplastics in drinking-water."
What should a Phoenix household actually do?
Decide what you're filtering for, then buy for that.
- Microplastics only, low effort: a faucet-mount or refrigerator filter listed for the NSF/ANSI 401 Microplastics Reduction claim. Change the cartridge on schedule.
- Microplastics plus taste, chlorine and other contaminants: an under-sink RO system or a plumbed-in certified filter at the kitchen tap.
- Whole-house hard water: that's a different job. Microplastic filters don't soften water; see whether you need a water softener or other treatment.
If you want an under-sink filter or RO system installed on a dedicated drinking tap, HQ Plumbing & Air handles that through our water softening and filtration service. We give free estimates, and we're licensed and insured.