NEW YORK — An estimated 1 in 10 Americans have been exposed to drinking water that contains dangerous chemicals or fails to meet a federal health benchmark in other ways, an investigation by The New York Times has found. A report of the investigation was published in the September 13 edition of the newspaper.

“Those exposures include carcinogens in the tap water of major American cities and unsafe chemicals in drinking-water wells. Wells, which are not typically regulated by the Safe Drinking Water Act, are more likely to contain contaminants than municipal water systems,” the report said. It notes that many who consume dangerous chemicals through their drinking water do not realize it because “most of today’s water pollution has no scent or taste.”

The Times said its research included the review of “hundreds of thousands of water pollution records” from all 50 states and the US Environmental Protection Agency (EPA) obtained through Freedom of Information Act requests, as well as from more than 250 interviews with state and federal regulators, water-systems managers, environmental advocates and scientists. The Times compiled a national database of water pollution violations “that is more comprehensive than those maintained by states or the EPA,” the report said.

The Times says its research shows that 40 percent of the nation’s community water systems violated the Safe Drinking Water Act at least once last year. “Those violations ranged from failing to maintain proper paperwork to allowing carcinogens into tap water. More than 23 million people received drinking water from municipal systems that violated a health-based standard,” the report said.

The Times reported that the federal Clean Water Act, a water pollution-control law passed in 1972, has been violated more than 506,000 times since 2004, by more than 23,000 companies and other facilities, according to reports submitted by polluters themselves. “Companies sometimes test what they are dumping only once a quarter, so the actual number of days when they broke the law is often far higher. And some companies illegally avoid reporting their emissions, say officials, so infractions go unrecorded,” according to the report.

The Times said its research reveals that fewer than 3 percent of Clean Water Act violations resulted in fines or other significant punishments by state officials, and that the EPA often declined to prosecute polluters or force states to strengthen their enforcement.

The report looks at shortcomings of the EPA, and quotes from an interview with EPA Administrator Lisa P. Jackson, appointed earlier this year by President Obama. Jackson said that despite many successes since the Clean Water Act was passed, the nation’s water today does not meet public health goals and enforcement of water pollution laws is “unacceptably low.” Jackson said she intends “to work on these water issues pretty broadly across the country.”

The online version of the report also includes a video documentary in which one West Virginia mother explains how water pollution, which she believes is caused by nearby coal companies, has impacted her family and community.

A related article, “How safe is your water?,” offers information for consumers to use to consider the safety of their water, including when and what water treatment devices might be useful.

The report is part of The New York Times series, “Toxic Waters,” which is about the worsening pollution of America’s waters and regulators’ response.

For an interactive version of the Times national database of water pollution violations, which can show violations by community, click here.

To read the full report, click here.

For related information, click here, here or here.