The following citations are drawn from peer-reviewed scientific journals, U.S. government agencies (USGS, EPA, CDC), and independent research organizations. Every statistic on this page is sourced. Every claim is verifiable. We do not ask you to trust our marketing — we give you the primary sources.
The Regulatory Gap
The EPA regulates fewer than 100 contaminants in public drinking water. Scientists have identified over 316 chemicals in U.S. tap water. The gap between what is regulated and what is present is where your family's health risk lives.
316+
Contaminants Detected in U.S. Tap Water
<90
Contaminants with EPA Legal Limits
226+
Contaminants with Zero Legal Protection
Source: EWG Tap Water Database; EPA National Primary Drinking Water Regulations. The EPA has not added a new contaminant to its regulated list since 1996.
Primary Source Citations
The Evidence, Contaminant by Contaminant
CRITICALSynthetic Fluorinated Compounds
PFAS / Forever Chemicals
2023
At least 45% of U.S. tap water contains PFAS 'forever chemicals'
The U.S. Geological Survey conducted the most comprehensive national PFAS tap water study to date, testing both public water supplies and private wells across all 50 states. Researchers detected at least one PFAS compound in an estimated 45% of U.S. drinking water samples. Urban and suburban areas showed the highest contamination rates. PFAS are not removed by conventional water treatment and persist indefinitely in the environment and human body.
Key Finding
45% of U.S. tap water samples contain detectable PFAS. Detection rates were highest in urban areas and near industrial sites.
Health Risk
PFAS exposure is linked to kidney and testicular cancer, thyroid disease, immune suppression, and developmental disorders in children. The EPA classified PFOA and PFOS as human carcinogens in 2024.
Over 200 million Americans served by water systems with detectable PFAS
Environmental Working Group researchers analyzed EPA data and estimated that more than 200 million Americans are served by public water systems containing PFOA or PFOS at concentrations above 1 part per trillion — a level toxicologists consider the threshold for health concern. The EPA's own enforcement data confirmed widespread contamination in water systems serving communities of all sizes.
Key Finding
200+ million Americans receive water from systems with PFAS levels above what toxicologists consider safe.
Health Risk
Even at concentrations of 1 part per trillion, PFAS exposure is associated with increased cancer risk, hormonal disruption, and suppressed immune response in children.
Source: Environmental Working Group (EWG) / EPA Data Analysis, 2020–2024
Lead contamination found in water systems serving 250+ million Americans
The Natural Resources Defense Council analyzed EPA compliance data and found worrisome lead levels in water systems serving more than 250 million people across the United States. Lead enters drinking water primarily through lead service lines, lead solder in plumbing, and brass fixtures — infrastructure that remains widespread in homes built before 1986. The CDC and EPA both state that no safe level of lead exposure exists.
Key Finding
Water systems serving 250+ million Americans have reported lead levels above zero — the only scientifically safe threshold.
Health Risk
Lead causes irreversible neurological damage in children, reducing IQ and causing behavioral disorders. In adults, it is associated with kidney disease, cardiovascular disease, and hypertension. No safe exposure level has ever been established.
Source: Natural Resources Defense Council (NRDC), April 2025
Chromium-6 detected in drinking water of 218+ million Americans — no federal limit exists
EWG's analysis of federal drinking water data found hexavalent chromium (chromium-6) — the 'Erin Brockovich chemical' — in the tap water of more than 218 million Americans across 48 states. A 2008 National Toxicology Program study confirmed chromium-6 causes cancer in laboratory animals when ingested. Despite this, the EPA has never set a maximum contaminant level specifically for chromium-6 in drinking water.
Key Finding
Chromium-6 present in water supplies serving 218 million Americans. For 231 million people, average levels exceed the one-in-a-million cancer risk threshold.
Health Risk
Chromium-6 is a Group 1 human carcinogen (IARC). Chronic ingestion is associated with stomach cancer. The National Toxicology Program confirmed carcinogenicity in animal studies at levels comparable to those found in U.S. tap water.
Source: Environmental Working Group (EWG), 2016–2017
Trihalomethanes in chlorinated water linked to elevated bladder cancer risk
A pooled analysis published in Epidemiology combined data from multiple studies examining the relationship between trihalomethane (THM) exposure — a byproduct of chlorinating water containing organic matter — and bladder cancer. The analysis found a statistically significant association between long-term exposure to chlorinated drinking water and increased bladder cancer incidence. THMs are classified as possible human carcinogens by the IARC, and the EPA regulates them under the Disinfection Byproducts Rule.
Key Finding
Long-term exposure to chlorination byproducts (THMs) is associated with a 35–50% elevated risk of bladder cancer in multiple pooled epidemiological analyses.
Health Risk
Trihalomethanes (chloroform, bromodichloromethane, dibromochloromethane, bromoform) form when chlorine reacts with naturally occurring organic matter. They are absorbed through drinking, cooking, and showering.
Source: Villanueva et al., Epidemiology, 2004 / Science of the Total Environment, 2025
EPA arsenic limit 500x higher than what toxicologists consider truly safe
The EPA's current maximum contaminant level for arsenic in drinking water is 10 micrograms per liter (10 ppb), set in 2001. However, a landmark study published in Science (Smith et al., 2002) demonstrated that bladder cancer risk increases at arsenic concentrations well below this limit. The National Academy of Sciences estimated that the 10 ppb standard still results in a cancer risk of approximately 1 in 300 — far above the EPA's own 1-in-10,000 acceptable risk threshold for other contaminants.
Key Finding
At the EPA's current 10 ppb limit, estimated lifetime cancer risk from arsenic is approximately 1 in 300 — 33x higher than the EPA's own acceptable risk threshold.
Health Risk
Arsenic is a Group 1 human carcinogen (IARC). Chronic exposure causes bladder, lung, and skin cancers. It also causes peripheral neuropathy, cardiovascular disease, and diabetes at sub-regulatory concentrations.
Source: Smith et al., Science, 2002 / National Academy of Sciences
94% of U.S. tap water samples test positive for plastic fibers
Orb Media, in collaboration with researchers at the University of Minnesota, tested tap water samples from locations across the United States — including the EPA headquarters, Trump Tower, and congressional buildings in Washington D.C. — and found that 94% of samples contained microscopic plastic fibers. The U.S. had the highest contamination rate of any country tested. Subsequent peer-reviewed studies have confirmed microplastic presence in tap water globally, with concentrations varying by source and treatment method.
Key Finding
94% of U.S. tap water samples contain microplastic fibers. The U.S. has the highest contamination rate globally among countries tested.
Health Risk
Microplastics carry adsorbed pesticides, heavy metals, and endocrine-disrupting chemicals. They have been detected in human blood, lung tissue, and placentas. Long-term health effects are under active investigation; no safe exposure level has been established.
Hormones and pharmaceuticals detected in groundwater used for drinking across the U.S.
A USGS study published in Environmental Science & Technology analyzed groundwater samples from drinking water supply wells across the United States and detected hormones and pharmaceuticals in a significant proportion of samples. Compounds detected included antibiotics, synthetic hormones (including birth control compounds), antidepressants, and chemotherapy drugs. Conventional water treatment processes are largely ineffective at removing these compounds.
Key Finding
Hormones and pharmaceuticals detected in U.S. drinking water supply groundwater. Conventional treatment does not remove these compounds. Up to 80% of U.S. streams contain detectable pharmaceutical residues.
Health Risk
Endocrine-disrupting compounds (synthetic estrogens, hormones) can interfere with human hormonal systems at extremely low concentrations. Antibiotic residues in water contribute to the development of antibiotic-resistant bacteria — a recognized global health crisis.
Source: Bexfield et al., Environmental Science & Technology, 2019 / Cary Institute, 2023
Nitrate in drinking water linked to colorectal cancer and thyroid disease
A comprehensive review published in the International Journal of Cancer found that nitrate exposure from drinking water is associated with increased risk of colorectal cancer, thyroid disease, and neural tube defects. Nitrates enter water supplies primarily through agricultural fertilizer runoff and are detected in approximately 1 in 5 private wells in agricultural regions of the U.S. The EPA's maximum contaminant level of 10 mg/L was set primarily to protect against acute methemoglobinemia ('blue baby syndrome') in infants — not long-term cancer risk.
Key Finding
Nitrate exposure from drinking water is associated with colorectal cancer risk. Detected in 1 in 5 U.S. private wells. The EPA's limit does not account for long-term carcinogenic risk.
Health Risk
Nitrates convert to nitrosamines in the body — potent carcinogens. In infants, nitrate causes methemoglobinemia (blue baby syndrome), which can be fatal. Chronic adult exposure is linked to colorectal cancer and thyroid dysfunction.
Source: Temkin et al., Environmental Health, 2019 / International Journal of Cancer
Every contaminant documented on this page is targeted by at least one stage of AION's seven-stage filtration architecture. The table below maps each contaminant to the specific stage responsible for its removal.
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All citations on this page link to primary sources including peer-reviewed journals, U.S. government agencies (USGS, EPA, CDC, NCI), and independent research organizations. AION WATER does not manufacture or alter scientific data. Health risk statements reflect findings from the cited studies and do not constitute medical advice. For health concerns related to water quality, consult a licensed physician or certified water quality professional.