• Tap water often contains harmful contaminants including PFAS, arsenic, nitrates, lead, and trihalomethanes at levels far above what health experts consider safe.

• Dozens of new contaminants are identified each year, yet many remain unregulated or poorly regulated.

• EPA legal limits are frequently outdated and can be far higher than modern health guidelines recommended by organizations like the Environmental Working Group (EWG).

• Certain contaminants pose serious health risks like cancer, endocrine disruption, developmental harm, reproductive issues, immune dysfunction, and neurological damage.

• Vulnerable groups such as infants, children, and pregnant women face the greatest risks, especially from contaminants like nitrates, lead, PFAS, microplastics, and TCE.

• Even treated water can contain dangerous byproducts, such as trihalomethanes and chloramines, created during the disinfection process.

Millions of people rely on tap water every day—but how safe is it?

The Environmental Protection Agency (EPA) regulates certain contaminants, but many of its legal limits are far less strict than the health-based guidelines recommended by researchers at the Environmental Working Group (EWG). 

And even with treatment, water quality can vary drastically from one state to the next, leaving many Americans unaware of the dangers flowing from their own taps.

Water quality standards and testing practices vary from state to state, which means there’s no definitive ranking of the “dirtiest” drinking water. 

This list highlights the states with the highest number of contaminants detected in tap water, based on the latest findings from the EWG’s updated Tap Water Database.

No matter where your state ranks, it’s important to take proactive steps to protect yourself and your family from chemicals, heavy metals, and other contaminants. Get your Free Water Report and see what’s in your local water supply and get personalized recommendations for safer, cleaner drinking water.

• Tap water in Connecticut may contain as many as 120 contaminants.

• Chemicals found in Connecticut water systems include haloacetic acids, bromodichloromethane, dichloroacetic acid, and chloroform.

• New data obtained by The Connecticut Mirror shows there could be as many as 8,000 lead service lines still in use in public water systems throughout the state.

• Tap water in Washington may contain as many as 121 contaminants.

• Kennewick has found PFAS levels above the state standard.

• Several utilities in the state have levels of arsenic, HAA5, and TTHMs above the legal limits in their water supply.

• Tap water in Pennsylvania may contain as many as 123 contaminants.

• More than 180 providers across the state continue to detect PFAS at levels above more restrictive federal regulations

• More than half of private wells in Pennsylvania don't meet drinking water standards, with around 40% having high levels of contaminants like nitrate

• A study found a toxic byproduct of chloramine is in one-third of Pennsylvania’s drinking water.

• Tap water in Florida may contain as many as 126 contaminants.

• The city of Cocoa’s water systems exceeded EWG's guideline by 308 times for HAA5, 724 times for HAA9, and 333 times for TTHMs. 

• Another South Florida city detected PFAS in its water at a level exceeding federal guidelines. Stuart city managers got millions of dollars from 3M as part of a class action settlement to pay for future water filtration facilities.

• Tap water in Wisconsin may contain as many as 130 contaminants.

• Residents of Williams Bay were warned not to drink or cook with tap water after tests revealed dangerously high levels of nitrite contamination. The warning comes after the Walworth County Health Department confirmed a case of "blue baby syndrome," an illness often linked to contaminated drinking water.

• The Department of Natural Resources is providing bottled water to more than 1,700 families in communities where PFAS has contaminated 97.3% of all wells tested.

• Tap water in New Jersey may contain as many as 131 contaminants.

• PFOA levels reached 36.1 ppt—over twice the state limit of 14 ppt—resulting in a violation notice and leading to a $4.9 million settlement for roughly 60,000 affected residents.

• A private well in Warren County tested for some of the highest PFAS levels ever recorded in New Jersey—and among the highest in the nation.

• Tap water in Massachusetts may contain as many as 132 contaminants.

• More than 80% of taps in Massachusetts schools and child care centers tested positive for lead, exposing children to a toxic metal linked to nervous system damage, stunted growth, ADHD, and serious behavioral and mental health issues.

• Test results showed HAA5 levels above the maximum contaminant limit in drinking water samples.

• Tap water in California may contain as many as 175 contaminants.

• California's drinking water has elevated levels of arsenic, which has been linked to a higher chance of babies being born preterm, with lower birth weights, or smaller than expected for their gestational age.

• Residents in wildfire zones are at heightened risk of exposure to benzene and vinyl chloride, two potent carcinogens linked to some of the most serious long-term health effects.

It is estimated that 177 California drinking water systems, serving over 18.9 million people, have had elevated PFAS levels

• Tap water in New York may contain as many as 197 contaminants.

• An estimated 189 New York drinking water systems, serving over 1.3 million people, have had elevated levels of PFAS. 

• 3.1 million New Yorkers—about 15% of the state’s population—receive drinking water through confirmed or suspected lead pipes. Buffalo has one of the highest rates among major cities outside New York City, with 45% of its service lines confirmed to contain lead.

• Hexavalent chromium, or chromium-6, was detected in New York City’s water at twice EWG’s health guideline.

• Tap water in Texas may contain as many as 207 contaminants.

• More than 700 water systems in Texas — reaching 8.6 million people — had TTHM levels above the EPA’s legal limit of 80 parts per billion. Texas has more medium, large and very large water systems with unsafe TTHM levels than other state.

• A 2025 updated assessment of aquifers in Texas found that some groundwater-sourced systems still found elevated arsenic concentrations above health-based recommendations

Bottled water might feel like the safer choice, but in many cases, it’s no better than tap water. The FDA holds bottled water to the same standards the EPA sets for tap water, and many brands simply bottle municipal water. Add in the microplastics that leach from plastic packaging, and it’s clear bottled water isn’t the cleaner alternative many expect. Learn more about the hidden risks of bottled water here.

Water standards aren’t always enough to protect against contaminants out of your tap—and many common filtration systems fall short.

Reverse osmosis systems and carbon filters barely scratch the surface when it comes to water filtration. The most effective way to protect your health is with a filtration system you can trust. Clearly Filtered removes up to 99.99% of 365+ contaminants—including the ones most commonly found in tap water.

See our lab results and choose cleaner, safer water for your home.