Primary sources · EPA & USGS · Plain English
Is This In Your Water?
Evidence library

What the government actually says.

Eight primary sources from the U.S. EPA and the U.S. Geological Survey, in plain English. For each one we show what it says, the date, and what it does not prove.

8 sourcesEvery link opens the agency's own pageLast checked Oct 9, 2026
// how to read this

Facts first. Our words second.

QuotesWords in quotation marks were checked word for word against the agency's page.
SummariesEverything else is our plain-English summary, and it links to the source.
LimitsEvery source carries a "does not prove" line, so nothing gets stretched.
// three short guides

Start with a question.

01

Can water affect health over time?

What EPA says about long-term exposure, and what "lifetime" health advisories are.

Read the guide → 02

Legal limits vs. health goals

Why the enforceable limit and EPA's health goal aren't always the same number.

Read the guide → 03 Proposal

PFAS rules in 2026

What was finalized in 2024, and what EPA proposed to change in May 2026.

Read the guide →
// the sources

Every source, dated.

Health and long-term exposure

2 sources
EPAReport on the EnvironmentAgency explainer

Drinking Water

Page last updated May 27, 2026

EPA explains that drinking water with unsafe levels of contaminants "can cause health effects, such as gastrointestinal illnesses, nervous system or reproductive effects, and chronic diseases such as cancer." It adds that lower doses over long periods can lead to chronic conditions, that the effects of some contaminants are not yet well understood, and that risk depends on the contaminant, its concentration, the person, how much water they drink and for how long.

What this does not proveThat any particular water system, or your tap, has unsafe levels. It describes what can happen when levels are unsafe.

Open on epa.gov Last checked Oct 9, 2026
EPASafe Drinking Water ActAgency explainer

Drinking Water Health Advisories (HAs)

Page last updated Mar 30, 2026

For some contaminants, EPA publishes health advisories: levels below which health effects aren’t expected over set exposure periods "(e.g., 1 day, 10 days, a lifetime)." EPA says advisories are not legally enforceable standards and can change as new information comes in.

What this does not proveThat water above an advisory level is illegal, or that it will cause harm. Advisories are guidance, not limits.

Open on epa.gov Last checked Oct 9, 2026

Legal limits and health goals

1 source
EPAGround Water and Drinking WaterRegulation reference

National Primary Drinking Water Regulations

Page last updated Aug 31, 2026

EPA’s master table of regulated contaminants. It defines the health goal (MCLG) as "the level of a contaminant in drinking water below which there is no known or expected risk to health" and calls goals "non-enforceable public health goals." The enforceable limit (MCL) is "set as close to MCLGs as feasible," with treatment technology and cost taken into account.

What this does not proveThat water between the goal and the legal limit is unsafe for everyone. It shows the two numbers can differ, and why.

Open on epa.gov Last checked Oct 9, 2026

PFAS ("forever chemicals")

5 sources · 3 are about proposals
EPANews releaseFinal rule announced

Biden-Harris Administration Finalizes First-Ever National Drinking Water Standard to Protect 100M People from PFAS Pollution

Published Apr 10, 2024

EPA’s announcement of the first national, legally enforceable drinking-water standard for several PFAS. Its stated rationale: "Exposure to PFAS has been linked to deadly cancers, impacts to the liver and heart, and immune and developmental damage to infants and children."

What this does not proveThat PFAS are in your water, or at what level. Parts of this 2024 rule are the subject of the 2026 proposals below.

Open on epa.gov Last checked Oct 9, 2026
USGSNational news releaseStudy estimate

Tap water study detects PFAS ‘forever chemicals’ across the US

Published Jul 5, 2023

A USGS study of tap water sampled at 716 locations from 2016 to 2021, covering both private wells and public supplies. USGS estimates that at least 45% of the nation’s tap water could have one or more types of PFAS. The study tested for 32 of the more than 12,000 types of PFAS.

What this does not proveThat 45% of taps have PFAS. It is a national estimate from a sample, and most exposure was found near urban areas and likely PFAS sources.

Open on usgs.gov Last checked Oct 9, 2026
EPANews releaseAnnounces proposals

EPA Advances Comprehensive PFAS Strategy with Legally Defensible, Practical, Scientifically Sound Drinking Water Protections

Published May 18, 2026

EPA announced its PFAS strategy, including nearly $1 billion in grant funding for PFAS and other emerging contaminants in drinking water, and two proposed rules: one to give eligible systems more time to meet the PFOA and PFOS limits, and one to rescind rules for four other PFAS.

What this does not proveThat any rule has changed yet. These are proposals, and they could be finalized, changed or withdrawn.

Open on epa.gov Last checked Oct 9, 2026
EPASafe Drinking Water ActProposal

Proposed PFOA and PFOS Compliance Extension Rule

Proposed May 18, 2026 · page updated Oct 8, 2026

The proposal would let eligible water systems "request two additional years - to 2031" to meet the PFOA and PFOS limits. The extension would not be automatic. The limits themselves would "remain 4.0 parts per trillion (ppt) each." The comment period closed July 20, 2026.

What this does not proveThat the deadline has moved. As of our check, EPA still lists this as a proposed rule.

Open on epa.gov Last checked Oct 9, 2026
EPASafe Drinking Water ActProposal

Proposed PFAS Rescission Rule

Proposed May 18, 2026 · page updated Oct 8, 2026

EPA proposed rescinding its regulations for PFHxS, PFNA, HFPO-DA (known as GenX) and Hazard Index mixtures that include PFBS. EPA says the reason is a procedural problem in how the rules were made, and that it will evaluate additional PFAS for possible future regulation. The comment period closed July 20, 2026.

What this does not proveThat these chemicals are safe. EPA’s stated reason is about the rulemaking process, not a new health finding.

Open on epa.gov Last checked Oct 9, 2026

Plain-English summaries are ours. Words in quotation marks were checked word for word against the agency page on Oct 9, 2026. Links go to the agency's own site. EPA and USGS do not endorse this site or any product. This is general education, not medical advice.

// your water

Then look at your town.

National facts only go so far. Your ZIP report shows what the EPA has on record for your water system. On a private well? Public records won't cover it, so testing is up to you.