Flint, Michigan is in a state of emergency after dangerous levels of lead in its drinking water were found to cause lead poisoning in scores of children. But citizens of this Midwest city may not be the only Americans at risk. The Guardian has reportedly come across a set of documents detailing questionable water testing practices in major cities like Detroit and Philadelphia, as well as the state of Rhode Island.

Water tests are being manipulated in “every major U.S. city east of the Mississippi,” an anonymous source intimately familiar with lead and copper regulations told The Guardian. “By word of mouth, this has become the thing to do in the water industry. The logical conclusion is that millions of people’s drinking water is potentially unsafe.”

It’s currently unknown whether Environmental Protection Agency (EPA) regulations have been explicitly violated, but The Guardian’s source indicates the agency’s guidelines have been overstepped and ignored. Specifically, the documents demonstrate that water authorities across the U.S. have purposefully cut corners to ensure their water systems don’t fail lead and copper testing standards.

The EPA was given a day to respond to the Guardians' allegations, but did not prior to press time.

Prompted by the ongoing issues in Flint, Dr. Yanna Lambrinidou, a senior environmental scientist at Rhode Island’s Department of Health, first obtained the documents through a request for details on water testing procedures under the Freedom of Information Act, and then shared them with the Guardian. She hopes to determine whether other cities are drinking unclean and unsafe water.

Poisoned In Flint

The water problem in Flint has lingered for almost two years; however, the issue has only garnered national attention in recent months. In April 2014 , Flint began temporarily drawing its water from the Flint River instead of Detroit’s water supply in order to save money while authorities waited on a new water system to be installed in 2016. The city of roughly 100,000 immediately began receiving water from the extremely corrosive Flint River, which contained high levels of chloride. This water, which should have been treated with an anticorrosion agent per federal regulations, remained untreated.

Residents immediately complained of the smell, taste, and appearance of the water. Little did they know the chloride from the river was eroding the city’s water pipes, and drawing lead out of them — and into every person’s cup, bathtub, and sink. Nearly a year later, in March 2015, officials announced Flint’s water quality had improved, and that it met all state and federal safety standards. A few months later, in September, a group of doctors urged Flint residents to stop using water from the river after they found high levels of lead in children’s blood.

According to the EPA , lead can harm almost every organ and system in the body if it’s consumed. Children are particularly susceptible to both short- and long-term effects, such as behavior and learning problems, a lower IQ, slowed growth, hearing problems, and anemia.

In October, the Michigan legislature approved $9.4 million in aid to Flint, as well as a plan to move back to using Detroit’s water supply. Then in January, Flint declared a state of emergency and President Obama stepped in to sign an emergency declaration, which authorized the Federal Emergency Management Agency and the Department of Homeland Security to initiate relief efforts, such as bottled water donations .

“There is no way that Flint is a one-off,” Lambrinidou told the Guardian . “There are many ways to game the system. In Flint, they went to test neighborhoods where they knew didn’t have a problem. You can also flush the water to get rid of the lead. If you flush it before sampling, the problem will go away.”

Beyond Flint

The documents obtained by Lambrinidou revealed testing methods that are openly criticized and unapproved by the EPA. These practices include running tap water long enough to flush out lead before testing, as well as removing filters from taps. Water testers also asked residents to run only cold water for two minutes before collecting a test sample (this reportedly happened in Philadelphia, though there’s a chance the practice is more widespread). Under normal circumstances, this test would be five minutes long, and it would measure all elements of the water from the time the tap is opened to the time it’s closed — in other words, this test was repeatedly cut short. This method, called “pre-flushing” pipes, is controversial because it leads to an inaccurate test result, even if it is an official test.

“The EPA has completely turned its gaze away from this,” Lambrinidou said. “There is no robust oversight here, the only oversight is from the people getting hurt. Families who get hurt, such as in Flint, are the overseers. It’s a horrendous situation. The system is absolutely failing.”

The EPA has not decided whether it should move forward with recommendations from a panel that included Lambrinidou. But according to a report by the American Water Works Association, if water tests are being conducted improperly, roughly 96 million Americans are at risk for drinking unsafe water. Officials say correctly testing the water and correcting any issues with inaccurate tests could take years to fix.