Harmful Contaminants Detected in “Almost All Water Systems” in the U.S.

• by Amber Baker

• Published March 31, 2025
• Environment

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According to a new report from the Environmental Working Group (EWG), almost all U.S. water systems contain detectable levels of harmful contaminants, including chemicals, heavy metals, and radioactive substances. The latest Tap Water Database update identified 324 contaminants in drinking water nationwide, raising grave concerns among environmental scientists. The findings, based on safety data from 50,000 water systems collected between 2021 and 2023, reveal that many contaminants exceed levels considered safe by scientists, even as federal water quality standards remain outdated and unchanged. New Hampshire was the only state that did not submit data.^{1 2}

The EWG is a non-profit organization dedicated to research and advocacy on environmental and public health issues, including toxic chemicals, agricultural practices, and consumer product safety. EWG uses the Tap Water Database to analyze water quality data from across the U.S. to expose contaminants, push for stricter regulations, and help consumers make informed decisions about their drinking water. “This is a wake-up call,” said EWG senior scientist Tasha Stoiber in a press release.^{1 2}

Forever Chemicals, Heavy Metals, and Other Toxins in Drinking Water

Some of the most alarming contaminants found in U.S. tap water, according to the report, include PFAS (also called forever chemicals) linked to cancer, hormone disruption, and immune system damage; volatile organic compounds (VOCs), many of which are carcinogenic and can cause liver, kidney, and nervous system damage; nitrate, which poses a serious risk to infants by interfering with oxygen delivery in the blood and is associated with certain cancers; heavy metals like lead and arsenic, which can cause neurological damage, developmental delays, and organ toxicity; hexavalent chromium, a potent carcinogen made infamous by the Erin Brockovich case in the 1990s; disinfection byproducts, which form when chlorine and other disinfectants react with organic matter and produce chemicals linked to bladder cancer and reproductive issues; radiological contaminants, including uranium and radium, which increase the risk of cancer and kidney toxicity; and fluoride, which has been linked to potential neurodevelopmental effects and thyroid dysfunction at high levels.¹

In September 2024, concerns over fluoride’s safety finally reached the federal level, prompting a landmark ruling—after four years in court—that could reshape national water regulations. A federal district court ordered the Environmental Protection Agency (EPA) to reassess its fluoride policies after finding “substantial and scientifically credible evidence” linking fluoride exposure to potential cognitive risks in children, compelling the agency to consider regulatory changes.

The court’s ruling also cites a 324-page systematic review by the National Toxicology Program (NTP), which found that 18 of 19 high-quality studies concluded with moderate confidence that higher fluoride exposure is associated with lowered IQ in children.³

Tap Water in U.S. a ‘Chemical Cocktail’ Contributing to 100,000 Cancer Cases

Contaminants in American tap water may be fueling a public health crisis, according to a groundbreaking 2019 study led by EWG scientists. “The impact of human activities on our environment inevitably trickles downstream, impacting our drinking water,” EWG senior science analyst Sydney Evans said in an interview. She suggested that many of the identified contaminants have long been present in tap water in the U.S. and are only being detected because of advances in scientific methods, while clarifying that some of the contaminants are new.^{1 2}

“I would argue that a lot of it has been the way that chemicals and industries are regulated in this country—allowing for a huge number of chemicals to be approved without a whole lot of underlying research to prove that they’re safe,” she says. ¹

“For too many Americans, turning on their faucets for a glass of water is like pouring a cocktail of chemicals,” EWG’s Tap Water Database says. That “cocktail,” according to the 2019 peer-reviewed study, could contribute to a staggering 100,000 cancer cases. Despite the growing body of evidence that proves drinking water contamination to be harmful, federal policy remains unchanged, with only one changed maximum contaminant limit in the nonprofit’s 30-year advocacy history.²

How to Protect Yourself from Contaminants in Tap Water

While completely avoiding exposure to environmental toxins is impossible, investing in a home water filter is the best way to protect yourself from harmful drinking water, Evans says. She suggests looking up the contaminants in your city’s drinking water and finding a filtration system that best fits your situation. Not all types of filters will be effective for all contaminants, but activated-carbon filter pitchers are most accessible and affordable, while a reverse-osmosis system will be more effective but come with a higher price tag.

Evans says bottled water should be avoided at all costs except in natural disasters or emergencies. “The main issue that we have with bottled water is that there’s really no guarantee that it’s any better than your tap water. Sometimes it can be, but a lot of times it’s not, and the testing, because it’s regulated by a different agency, is a lot less transparent.” Additionally, it’s less affordable, not eco-friendly, and the plastic can break down and end up in the water.¹

“While safe water ultimately depends on stronger state and federal regulation and infrastructure improvements, consumer awareness can drive change,” EWG states on its website. EWG Vice President of Government Affairs Melanie Benesh urges consumers to contact their legislators to advocate for stronger limits on drinking water contaminants and to preserve the PFAS limits enacted by the EPA last year. Those limits remain in limbo after the U.S. Court of Appeals in Washington, D.C. paused lawsuits from both water utilities and the chemical industry, granting the Trump administration more time to review the EPA regulations. According to the EPA, there is no safe exposure level for PFAS in drinking water, as they are carcinogens.^{1 2}

Weaker Water Protections Could Mean Even More Toxic Contaminants in U.S. Drinking Water

Last month, American Rivers—an organization dedicated to protecting and restoring waterways from remote mountain streams to urban rivers—raised alarms over the government’s proposed rollbacks to the Clean Water Act, warning that they could worsen the growing risks of contaminated drinking water. According to American Rivers, the proposed revisions would weaken protections for the streams and wetlands that serve as critical drinking water sources for millions of Americans. With fewer waterways under federal regulation, industries and agricultural operations could face looser pollution restrictions, increasing the likelihood that toxic runoff, heavy metals, and PFAS chemicals seep further into water supplies. This could place an even greater burden on already underregulated water systems, making it harder to meet health-based safety standards.⁴

“Our nation’s health, wealth, and security depend on healthy rivers and streams,” said Tom Kiernan, president and CEO of American Rivers. “Weakening the Clean Water Act threatens safe, reliable drinking water for tens of millions of Americans and could drastically increase water treatment costs for farmers. Our rivers were literally on fire prior to the Clean Water Act, and any step back to those days—any step to limit what water sources receive protections—is a step in the wrong direction. We urge the administration to listen to Americans, who overwhelmingly want clean, safe water.”⁴

The Safe Drinking Water Act (SDWA) of 1974 is the primary federal law regulating tap water to protect public health, yet it has only been amended twice—in 1986 and 1996—despite growing concerns over widespread chemical contamination. The EWG warns that the EPA’s legal limits for pollutants are outdated and insufficient, failing to reflect the latest science on the health risks of exposure.⁵

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