Reverse-Osmosis Filtered Water

Under-sink RO system.

86Minimal burden · out of 100

Evidence strengthstrong

How this score is built

100Start
95.4Chemical hazard 1 × 4.6−4.6
88.6Everyday exposure 2 × 3.4−6.8
86Persistence 1 × 2.6−2.6
MinimalThe band86 sits in 80–100.

What each input rests on

The three ratings behind the score, and the studies each rests on
Input	Rating	Evidence
Chemical hazard	1/10	unsourced input Searched 2026-10-05: The low rating reflects the dose left after filtering, which the exposure study already covers; no study rates it separately.
Everyday exposure	2/10	In North Carolina homes, all under-sink reverse-osmosis and dual-stage filters tested showed near complete removal of all PFAS evaluated. Assessing the Effectiveness of Point-of-Use Residential Drinking Water Filters for Perfluoroalkyl Substances (PFASs) · Environmental Science & Technology Letters 2020 DOI 10.1021/acs.estlett.0c00004 · Abstract · read 2026-10-02
Persistence	1/10	unsourced input Searched 2026-10-05: The low rating reflects the dose left after filtering, which the exposure study already covers; no study rates it separately.

Ratings are editorial. A study listed here supports the rating; it did not compute it. How the index is built

What this means for you

In a 2020 home study, under-sink reverse-osmosis and two-stage filters removed nearly all the PFAS tested. Like any filter, it works only while its membrane and pre-filters are replaced on schedule; RO also sends about a gallon of water to the drain for every gallon it treats.

Evidence strength: strong

Sources: US EPA — Identifying drinking water filters certified to reduce PFAS (updated 2025-11-18)

See where your whole exposure load is highest — free Exposure Score →

This entry and the whole Index, on your phone.