PFAS guides, definitive answers, primary sources
Ten pillar guides on PFAS in US drinking water. Each one cites every numeric threshold back to a federal rule, peer-reviewed paper, or NSF standard. Read these to understand what's behind the $15 brief, or to do the lookup yourself.
EPA's April 2024 PFAS MCL, the 6 regulated compounds
The first federally-enforceable PFAS MCLs: 4.0 ng/L for PFOA + PFOS, 10 ng/L for PFHxS/PFNA/HFPO-DA, plus a Hazard Index. Compliance by 2029.
UCMR 5 explained, how to read your utility's PFAS data
EPA's UCMR 5 (2023–2025) is the largest PFAS dataset ever collected. How to find your utility on NCOD and what the numbers mean.
PFOA + PFOS toxicology, cancer, immune, developmental effects
What ATSDR's 2021 profile, IARC Monograph 110 + 135, and the C8 Science Panel actually concluded about PFOA and PFOS in humans.
NSF/ANSI 53 P473 vs 58, which filter standard removes PFAS
NSF 42, 53, 53 P473, 58, 401, what each certification actually proves about PFAS removal. The P473 protocol is the one to look for.
Under-sink RO vs pitcher filters, real PFAS removal rates
The Duke University 2020 study: under-sink RO removes >94% of PFAS; most pitcher filters remove 0–30%. The data, by filter type.
PFAS in groundwater, the US hotspot map
USGS, EWG, and state-DEP data point to the same hotspots: AFFF firefighting-foam sites, Chemours Fayetteville, 3M Decatur, military bases.
C8 Science Panel + DuPont Washington Works, what we learned
The 2005 DuPont settlement created a 7-year independent science panel. It found "probable links" to six diseases. The data that built the 2024 MCL.
PFAS and pregnancy, EFSA TWI vs EPA guidance
EFSA's 2020 Tolerable Weekly Intake is 4.4 ng/kg body weight per week for the sum of four PFAS. What that means in pregnancy.
Home PFAS testing, Cyclopure, Tap Score, Eurofins
Three credible mail-in PFAS tests for tap water. EPA Method 537.1, NELAP accreditation, kit prices, sample-collection protocol.
State PFAS regulations stronger than EPA (MI, NJ, NH)
Michigan, New Jersey, New Hampshire set enforceable state PFAS MCLs years before the EPA. Per-compound thresholds, by state.