iStock/Thinkstock(WASHINGTON) — Nearly one in four Americans’ drinking water comes from untested or contaminated systems, according to a report released Tuesday by the Natural Resources Defense Council (NRDC).

The environmental advocacy group said more than 18 million people were served by community water systems in 2015 that had violated basic lead and copper regulations, and nearly two million Americans lived in communities with water systems that had arsenic rule infractions.

“Our research shows that in 2015 alone, nearly 77 million people were served by more than 18,000 community water systems that violated at least one Safe Drinking Water Act rule,” the report reads.

These violations of the Safe Drinking Water Act, which regulates about 100 contaminants found in drinking water, included exceeding health-based standards, failing to properly test water for contaminants, and failing to report contamination to state authorities or the public.

With the impending cuts to the Environmental Protection Agency, the federal agency may have a harder time enforcing these regulations, especially in rural America, according to Mae Wu, senior attorney with the NRDC.

“There’s a two-tiered drinking water system in this nation, and rural America is most at risk from the inequality. Small systems have the highest percentage of water violations, and it’s largely due to financial and technical capacity issues that will only get worse when the EPA cuts drinking water programs,” Wu said.

The report found that the states with the most offenses based on population were Texas, Florida, Pennsylvania, New Jersey and Georgia.

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