Your tap water might look crystal-clear, but there are a lot more contaminants floating around in there than you realize. An analysis of 28 million water records from nearly 500,000 American water utilities collected by the Environmental Working Group (EWG) reveals most Americans’ tap water contains contaminants at levels acceptable to the government, but may actually pose health risks to the people. 
I went to the database and put in every zip code I’ve ever lived in – you can test your water here – and each one tested positive for higher-than-acceptable levels of at least 3 carcinogens, including chloroform. Yummy. The EWG found that tens of thousands of water utilities contain levels of cancer-causing contaminants. What’s more, every single zip code the group looked at turned up some form of contamination.
A senior analyst at EWG, Sonya Lunder said:
“We’re attempting to fill a huge gap here. I have not yet found any that have zero contaminants.” 
EWG President Ken Cook said on the group’s website:
“Americans deserve the fullest picture possible of what’s in their tap water. But they won’t get that information from the government or, in many cases, from their utilities. The only place they’ll find that is EWG’s drinking water report.”
Cook noted that even if the contaminants in a water system fall below federal guidelines, that doesn’t mean the water is safe. This is because it has been 20 years since the U.S. Environmental Protection Agency (EPA) added a new contaminant to its list of regulated contaminants.
Since more than half of the contaminants found in U.S. tap water had no regulatory limit at all, the substances can be legally present even in high concentrations, and utilities must neither test for them nor inform residents about their presence.
“Just because your tap water gets a passing grade from the government doesn’t always mean it’s safe. It’s time to stop basing environmental regulations on political or economic compromises, and instead listen to what scientists say about the long-term effects of toxic chemicals and empower Americans to protect themselves from pollutants even as they demand the protective action they deserve from government.”
Nneka Leiba, EWG’s Healthy Living Science Director, added:
“One of the challenges for us was to first, get across the message that ‘legal’ isn’t safe.
The legal limits that are set for drinking water often include political and economic compromises. They’re not purely based on health limits, so that’s part of the education process.” 
Findings from the Analysis
According to the EWG, contaminants detected in the country’s tap water included:
- 93 linked to an increased risk of cancer. The presence of known or likely carcinogens exceeding established federal or state health guidelines were found in more than 4,000 water systems. The contaminants pose minimal but important health risks, but levels found in tap water are not legally enforceable.
- 78 associated with brain and nervous system damage.
- 64 linked to developmental problems in children or fetuses.
- 45 tied to hormone disruption.
- 38 that potentially cause fertility problems. 
Other concerning contaminants discovered by the analysis:
- Chromium-6, a carcinogen with no federal regulations, was found in the drinking water supplies serving 250 million Americans in all 50 states. If the contaminant sounds familiar, it’s likely because it was made notorious by the film “Erin Brockovich.”
- 1,4-Dioxane, an unregulated compound detected in tap water that supplies 8.5 million people in 27 states at levels above those the EPA considers to pose a minimal cancer risk.
- Nitrate was detected in more than 1,800 water systems in 2015, serving 7 million people in 48 states above the level that research by the National Cancer Institute shows increases the risk of cancer – a level just half of the federal government’s legal limit for nitrate in drinking water. Nitrate is common in rural communities, where the chemical comes from animal waste and agricultural fertilizers.