What’s in your tap water?

Miami’s numbers, against every benchmark

PFOS is about 8× the enforceable limit and roughly 1,600× the 2022 health advisory; PFOA is about 3× the limit and 3,000× the advisory. The health-based goal for both is zero — the EPA’s finding that no lifetime-safe level has been identified.

Sources: Miami-Dade County / City of Miami Beach 2025 Consumer Confidence Report · EPA NPDWR final rule (2024) · EPA Lifetime Health Advisory (2022). ppt = parts per trillion.

What is PFAS — and why it builds up

PFAS (say “PEE-fass”) are a family of thousands of man-made chemicals that make things non-stick, waterproof and stain-proof — and they are the active ingredient in the firefighting foam sprayed at airports and fire-training sites for 50+ years. They are built on the carbon–fluorine bond, the strongest in chemistry, so they do not break down — not in soil, not in water, not in the human body. That is why they are called “forever chemicals.” They are persistent (they don’t break down), bioaccumulative (they build up in blood and tissue), and biomagnifying (they concentrate up the food chain) — which is why total load matters, not any one compound.

Once you drink them, they bind to the proteins in your blood and leave only slowly: the body takes years to clear even half of a single dose — about 5 years for PFOS, up to 8 for PFHxS. In a home drinking the water every day, new PFAS arrive faster than old PFAS leave, so the amount in the body climbs year after year; peer-reviewed pharmacokinetics indicate the level in the blood settles at roughly 100× the level in the water. That is why the EPA’s health goal is zero — it has found no dose that is safe.

And it is not only what you drink. Because PFAS leave the body so slowly, what matters is your cumulative load — the sum of every water contact, every day, for years: cooking, coffee and ice, washing produce, and the warm-water, long-contact routes of bathing, showering and swimming, where emerging evidence shows PFAS can cross the skin. Small daily exposures across many ordinary moments add up to a body burden that keeps climbing.

Because it accumulates, PFAS matters most for the smallest and still-developing bodies: it crosses the placenta and passes into breast milk, and children take in far more water per pound of body weight than adults. Pregnant and nursing mothers, infants, and young children carry the most risk from the same water.

Long-term exposure is linked, in the EPA’s and independent scientific record, to kidney and testicular cancer, thyroid disease, ulcerative colitis, high cholesterol, and pregnancy-induced hypertension — the six “probable links” established by the 69,000-person C8 Health Project. Separately, peer-reviewed studies tie childhood exposure to a weakened vaccine response, to effects on brain and neurological development, and to lower birth weight. In 2023 the WHO’s cancer agency classified PFOA as a Group 1 human carcinogen, its highest category.

In Miami-Dade specifically, thyroid cancer is the 2nd-highest of Florida’s 67 counties and runs more than double the U.S. rate in the hardest-hit neighborhoods beside the airport — the same corridor where PFAS is highest. This is an association, not proof of cause; the map’s Health section lays out the evidence and the honest caveats. ⤒ Share

The good news: removing PFAS is a solved problem, not a theoretical one — proven methods remove up to 99.9% of it, including anion (ion) exchange, reverse osmosis, and atmospheric water generation. Reverse osmosis and ion exchange already run at municipal scale in neighboring Hialeah and North Miami Beach, and the same fix works at home \u2014 a certified anion-exchange stage into reverse osmosis, or an atmospheric water generator into reverse osmosis. A carbon or pitcher/fridge filter is a false comfort — it misses the short-chain PFAS and fades as it loads, so it is a stage, never the whole answer; and boiling only concentrates PFAS. Boiling does not; it only concentrates it.

Sources: EPA final PFAS drinking-water rule & zero health goal (2024) · Olsen 2007 & Li 2018 (elimination half-lives) · C8 Science Panel probable-link findings (2012) · IARC Group 1 classification of PFOA (2023) · Grandjean 2012, JAMA (childhood vaccine response) · SCAN360 (U. Miami Sylvester / Florida Cancer Data System), age-adjusted 2016–20 (Miami-Dade thyroid). Every figure traces to a primary source.

The limit keeps falling

The enforceable limit fell from an informal 70 to 4 in eight years, and the health-based goal is zero. When the goalposts move only one way, it is because the evidence keeps getting worse — yet most household habits still run on the old math.

Sources: EPA Lifetime Health Advisory (2016, 2022) · EPA final NPDWR — MCL & MCLG (April 2024).

The contamination isn’t new — the “safe” line just fell toward it

The federal government first measured PFOS in Miami’s drinking water in 2013 — 43 to 58 ppt across the county’s systems (EPA UCMR3). A decade later it is 31 to 38 (utility reports, 2023–25). The water did not get dramatically worse. What changed is the definition of “acceptable”: from no limit at all, to a 70 ppt advisory (2016), to a 4 ppt enforceable limit and a health goal of zero (2024). The line dropped roughly 18-fold — toward a contamination that was already there. (No finished-water PFOS was publicly reported for 2016–2022; UCMR3 ended in 2015 and UCMR5 did not begin until 2023.)

⤒ Share this   See the measured number for your own ZIP ▸

Sources: EPA UCMR3 Archival Data Finder (2013–15) · EPA UCMR5 Data Finder (2023–25) · Miami-Dade WASD Water Quality Reports 2023 (PFOS 38), 2024 (31), 2025 (33) · EPA Lifetime Health Advisories (2016; 2022) · EPA final NPDWR / MCLG (2024). UCMR3’s 40 ppt reporting floor undercounts the early values; CCR figures are the year’s highest distribution value.

It’s not one glass of water

The wrong question is “Is my drinking water filtered?” The right question is “What is my family’s total water exposure over the next 20 years — and how do I EFFICIENTLY reduce PFAS as close to 0.00 as possible?” Because PFAS stay in the body for years, small daily exposures across many ordinary moments add up to a rising cumulative body burden. The body does not distinguish the ounce you drink from the gallon you bathe in, breathe as steam, and absorb through skin.

Every home has more than one water pathway — ranked here by the weight of evidence:

The bath you put your child in is the same water you would not put in your own glass. Childhood is the one developmental window that cannot be repeated: a mother’s PFAS burden at conception becomes the infant’s starting burden, and the systems being built — brain, immune, hormones, bone — calibrate during exactly the years exposure is highest.

Sources: Ragnarsdóttir et al. 2024 (dermal absorption) · peer-reviewed shower-aerosol PM measurements · EPA (children more exposed per pound of body weight) · HOME Study (pediatric bone density) · Rigano Water Institute whitepaper (full citations). Association and cumulative-exposure science; not a prediction for any individual.

Two cities, two ways to get water

New York moves roughly a billion gallons a day to nearly 10 million people, almost entirely by gravity, from three protected watersheds up to 125 miles away — through tunnels like the 85-mile Delaware Aqueduct, the world’s longest. Because the land around the source is kept wild, the water arrives clean enough that the EPA permits it to run unfiltered. The design puts distance and protection between people and their water.

Miami-Dade’s design is the opposite. Its drinking water is pumped from the Biscayne Aquifer — an unconfined limestone formation whose top sits just 2 to 5 feet below the surface, so permeable that a spill at ground level reaches the water table quickly. Some of the wellfields sit right beside Miami International Airport, where firefighting foam was used for decades — and the treatment plants do not remove PFAS. There is little distance, and little protection, between the surface and the glass.

Sources: NYC DEP (Water Supply; Filtration Avoidance Determination) · National Academies review of the NYC Watershed Protection Program · USGS Fact Sheet 2019-3056 & Ground Water Atlas HA 730-G (Biscayne Aquifer) · Miami-Dade Wellfield Protection / Aquifer Recharge Element (2026). Inspired by “New York’s Genius Water Supply System,” Epic Maps.

Your child’s school drinks the same water

Schools on the airport side are fed by the Hialeah / Preston plants, whose wells sit beside 50 years of firefighting foam — the foam marker 6:2 FTS runs 190 ppt in that finished water. Schools fed by Alexander Orr, farthest from the airport, read 0. Same county, two different glasses.

Find your school and the report traces the whole chain — school → system → plant → wellfield → airport-side? → the finished-water PFOS — using the government’s own published numbers, nothing modeled.

Sources: Miami-Dade School Site geometry (County GIS) · EPA UCMR5 per-plant finished water · Miami-Dade / utility Consumer Confidence Reports. The plant number is finished water, not this school’s specific fountain.

Straight answers, rated by the evidence

Confidence reflects the weight of primary evidence, not opinion — ★★★★★ settled, ★★☆☆☆ still emerging. Every figure traces to the sections above. Treatment options are covered separately, evidence-rated and without brand recommendations.

How we know it’s the airport and firefighting foam

This is not new. The first nationwide federal PFAS survey (EPA UCMR3) measured it in South Florida’s finished drinking water more than a decade ago — and every system that reported was already 10 to 14 times over the 4 ppt limit the EPA would not make enforceable until 2024:

January 2020 — two years before the EPA cut its advisory, four years before any enforceable limit existed. The County sampled its wells and reported 6 of 89 over the then-current federal health advisory of 70 ppt. The Miami Springs wells it took out of service had been feeding the tap at 124, 182 and 184 ppt. Its own director later put it at 70 of 95 wells with detectable PFAS. Its own official confirmed the treatment plants “do not remove PFAS,” and the utility says it manages which wells it runs “to maximize output from more pristine sources.” The delivered number therefore measures the blending, not the source.

Sources: EPA UCMR5 (6:2 FTS per plant) · Florida DEP fire-training assessments (Fire Academy groundwater) · EPA UCMR3 Archival Data Finder 2013–15 (MIA PWS FL4134513, PFOS 47, 9/26/2013) · EPA final NPDWR 2024 (PFOS MCL 4 ppt — the multiple-over basis) · Miami-Dade DERM (2026-01-08) · WASD statements (2020-01-23; K. Lynskey; D. Yoder, Miami New Times) · In re AFFF Products Liability Litigation, MDL No. 2873 · FIU/Quinete (rainwater). Government and peer-reviewed records only; the well-by-well table remains an unreleased public record.

When another utility found PFAS, it warned people

In a formal Drinking Water Advisory, Walworth Waterworks in Wisconsin reported PFAS in one of its wells above health-based standards. Its state health department’s response was to tell residents to reduce their exposure: the Wisconsin Department of Health Services “recommends people limit their intake of PFAS compounds,” and advised limiting consumption of the utility’s water and using a certified anion-exchange → reverse-osmosis filter (NSF/ANSI 58). “Boiling water does not remove PFAS.”

Miami-Dade’s finished water runs about 8× the federal PFOS limit. It, too, is compliant — utilities are not required to meet the limit until April 2029. Its 2025 report calls the water “high-quality” and communicates its “excellence.” Two utilities, the same federal law, opposite messages. You decide which one is protecting your family.

One honest note: the Wisconsin advisory reflects the cautious agency position that skin contact is low-risk. Newer peer-reviewed work (Birmingham, 2024) finds many PFAS do absorb through skin — the science is still moving. Both agree drinking is the dominant route, and both point to the same certified filters.

Source: Walworth Waterworks / Wisconsin Department of Health Services Drinking Water Advisory; sample results via Wisconsin DNR ▸. Miami-Dade wording: Miami-Dade 2025 Water Quality Report.

What to do — three steps, no products

We do not sell filters.

The next chapter of the oldest public-health work

In 1842, the lawyer and reformer Edwin Chadwick showed — in his landmark 1842 report — that clean water is the foundation of a healthy population, and helped launch the sanitary revolution in Britain: engineered sewers, filtered municipal water, and the Public Health Act of 1848.

The payoff was the largest in the history of medicine. Readers of the British Medical Journal (BMJ) later voted that “sanitary revolution” — clean water and sewage disposal — the greatest medical advance since 1840, ahead of antibiotics and vaccines. Clean water alone drove roughly half of the U.S. mortality decline in the early 20th century and helped lift life expectancy from 47 to 63 years (Cutler & Miller, 2005).

That work removed what people could see and smell — the pathogens behind cholera and typhoid. In Miami-Dade, the water is microbially clear; that first battle was largely won. What it carries now is what the Victorians never faced: invisible, man-made industrial chemicals that do not break down and slowly accumulate. This is the next chapter of the same story — and the same principle holds: it is wiser, and historically cheaper, to protect the water at the source than to treat the consequences downstream.

Sources: Chadwick, 1842 (UK Parliament, Living Heritage) · Cutler & Miller, “The Role of Public Health Improvements in Health Advances,” Demography (2005) · BMJ readers’ poll (2007).

The evidence, with its sources

This library is a living document; entries are added and corrected as the science moves. Figures flagged ⚑ are directionally supported but await a specific indexed citation or are labeled inferences (e.g., the Amin & Burns cluster paper names radiation and iodine, not PFAS — the airport/AFFF overlay is our inference).