Congressman Mike Simpson has been on a crusade to allow more arsenic in drinking water.

For more than a decade, the eight-term Idaho Republican has fought battle after battle to permit higher levels of the toxic chemical in small-town water supplies.

The Environmental Protection Agency requires that drinking water contain less than 10 parts per billion of arsenic—a problem for states like Idaho, where higher levels of arsenic are found naturally in the water supply thanks to higher levels in the earth’s crust.

Simpson for years has objected to EPA rules on arsenic in drinking water, arguing that it creates a burden on rural communities that are ill equipped to upgrade their water-filtering systems.

In 2004, Simpson co-sponsored the Small Community Options for Regulatory Equity Act, which would have allowed small communities to be exempt from national drinking water regulations. He reintroduced this bill in 2010. In 2005, he co-sponsored a bill that would have directed the EPA to allow higher levels of arsenic in small-town drinking water for two years. None of these bills became law.

“Communities across Idaho have struggled to meet the federal government’s arsenic standards and are often forced to make difficult, even impossible, budget decisions in order to do so,” Simpson told The Daily Beast in a statement.

This week, Simpson was in the spotlight after a Center for Public Integrity report concluded he was the representative who stalled a scientific review of arsenic at the EPA. The review was necessary for the EPA to ban herbicides containing arsenic. ”All evidence from the Center’s investigation pointed to one congressman: Mike Simpson of Idaho,” the report said.

Simpson’s office told The Daily Beast they were short-staffed this week, and could not confirm or deny that the congressman worked to stall the arsenic review.

Simpson’s explanations don’t fly with water quality advocates, who note the deleterious public health effects that could come from not removing enough arsenic from water. Arsenic cause cancer, nervous system damage, and diabetes.

“There is no safe level of exposure to a genotoxic chemical—any exposure may incur some risk because genetic errors introduced in a single cell following arsenic exposure can cascade into cancer, birth defects and developmental damage,” said Dr. Kathleen Burns, director of Sciencecorps, a network of health professionals focused on environmental and occupational health.

Burns also argues that removing arsenic is an issue of racial justice. Arsenic can also cause cardiovascular disease, which African-Americans have greater genetic susceptibility for, she said.

The question should be how to pay for water treatment in rural areas, advocates say, not to allow more toxic chemicals there due to budget restraints.

“We never, ever question that cost is an issue. But we could never concede that cost is a reason to [lower] drinking water standards,” said Lynn Thorp, a senior policy specialist at Clean Water Action.

Castleford, a community of 300 in Simpson’s district, is one example of a town the congressman might have had in mind during his campaign to exempt small towns from EPA arsenic regulations.

It had a notorious problem with the toxic chemical in the local water supply. In 2004, the levels of arsenic in its drinking water was measured at more than double the EPA’s current limit. But its low population and overall budget of about $250,000 a year meant the construction of a filtration facility would place a large financial burden on the few hundred people living there. Castleford officials even considered a lawsuit against the EPA rule.

But in the end the city found a way to comply. With the help of federal funding and nonprofits dedicated to water quality in rural areas, the treatment facility was built for about $1 million. Now the water supply meets EPA standards for arsenic.

“Our question as a society... is how do we help people comply?” Thorp said. “We don’t agree that the way to solve this problem is to interfere with science or roll back drinking water standards.”