More than 20 percent of U.S. water treatment systems have violated key provisions of the Safe Drinking Water Act over the last five years, according to a report in The New York Times.

According to the Times, since 2004 the water provided to more than 49 million people has contained illegal concentrations of chemicals like arsenic or radioactive substances like uranium, as well as dangerous bacteria often found in sewage.

The Times reports that regulators were informed of each of those violations as they occurred. But regulatory records show that fewer than 6 percent of the water systems that broke the law were ever fined or punished by state or federal officials, including those at the Environmental Protection Agency.

For the full New York Times report on this story, click here.