"WASHINGTON — To ensure that tap water in the United States is safe to drink, the federal government has been steadily tightening the health standards for the nation’s water supplies for decades. But over and over again, local water systems around the country have failed to meet these requirements.

In a new study published in the Proceedings of the National Academy of Sciences, researchers found that, since 1982, between 3 and 10 percent of the country’s water systems have been in violation of federal Safe Drinking Water Act health standards each year. In 2015 alone, as many as 21 million Americans may have been exposed to unsafe drinking water.

The problem is particularly severe in low-income rural areas, the study found. And the researchers identified several places, including Oklahoma and West Texas, that have repeatedly fallen short in complying with water safety rules issued by the Environmental Protection Agency over the past decade."

Brad Plumer and Nadja Popovich report for the New York Times February 12, 2018. [2]