Unfiltered Tap Water

Municipal drinking water, straight from the tap.

44Moderate burden · out of 100

Cleaner swapA filter certified to NSF/ANSI 53 or 58 for the contaminant in your water

How this score is built

100Start
81.6Chemical hazard 4 × 4.6−18.4
54.4Everyday exposure 8 × 3.4−27.2
44Persistence 4 × 2.6−10.4
ModerateThe band44 sits in 40–59.

What each input rests on

The three ratings behind the score, and the studies each rests on
Input	Rating	Evidence
Chemical hazard	4/10	Pooling 6 case-control studies (2,806 cases), men averaging more than 1 µg/L of trihalomethanes had an odds ratio of 1.24 for bladder cancer, and 1.44 above 50 µg/L; no association was seen in women. Disinfection byproducts and bladder cancer: a pooled analysis · Epidemiology 2004 DOI 10.1097/01.ede.0000121380.02594.fc · PMID 15097021 · Abstract, Results · read 2026-10-02
Everyday exposure	8/10	In US EPA monitoring data from 2013-2015, drinking water supplies for 6 million US residents exceeded the 70 ng/L lifetime health advisory for PFOS and PFOA. Detection of Poly- and Perfluoroalkyl Substances (PFASs) in U.S. Drinking Water Linked to Industrial Sites, Military Fire Training Areas, and Wastewater Treatment Plants · Environ Sci Technol Lett 2016 DOI 10.1021/acs.estlett.6b00260 · PMID 27752509 · Abstract · read 2026-10-02
Persistence	4/10	After Ronneby, Sweden, stopped supplying PFAS-contaminated municipal water, residents’ mean serum half-lives were estimated at 5.3 years for PFHxS, 3.4 years for PFOS and 2.7 years for PFOA. Half-lives of PFOS, PFHxS and PFOA after end of exposure to contaminated drinking water · Occup Environ Med 2018 DOI 10.1136/oemed-2017-104651 · PMID 29133598 · Abstract, Results · read 2026-10-02

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

It scores as it does mainly because of how much everyday contact it involves. Quality varies widely by region. Common concerns are disinfection by-products, lead from old pipes, and trace PFAS. What a home filter removes depends on its type and on what it is certified to reduce — check the certifier’s listing for your contaminant.

Evidence strength: moderate

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

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