Millions of Americans are being forced to drink dangerous and dirty water containing arsenic, uranium and bacteria, as more than 20 percent of the nation's water treatment systems have been violating key provisions of the Safe Drinking Water Act.
According to a New York Times analysis of government data, since 2004, the water provided to more than 49 million people has contained illegal concentrations of chemicals, radioactive substances as well as dangerous bacteria often found in sewage.
The paper compiled and analyzed millions of records from water systems and regulators around the nation.
The data shows that violations have occurred in parts of every state. In the prosperous town of Ramsey, N.J., drinking water tests since 2004 have detected illegal concentrations of arsenic, a carcinogen, and the dry cleaning solvent tetrachloroethylene, which has also been linked to cancer.
In New York State, 205 water systems have broken the law by delivering tap water that contained illegal amounts of bacteria since 2004.
However, only six systems were ever fined or punished.
Experts say that the problem is that enforcing the Safe Drinking Water Act has not been a federal priority.
"There is significant reluctance within the E.P.A. and Justice Department to bring actions against municipalities, because there's a view that they are often cash-strapped, and fines would ultimately be paid by local taxpayers," said David Uhlmann, who headed the environmental crimes division at the Justice Department until 2007.
On Tuesday, the Senate Environment and Public Works committee will question the Environmental Protection Agency (EPA) about the enforcement of drinking-water safety laws.
The E.P.A. is expected to announce a new policy for how it polices the nation's 54,700 water systems.