State records show the tap water supply, which is used by 30,000 Colorado residents, had levels of naturally occurring uranium and radium radionuclides higher than current standards, The Denver Post reported Sunday.

Environmental Protection Agency official Jack Rycheky said implementing a better water treatment system in those affected communities would likely cost millions of dollars.

"When you've got a couple million customers tied in, you can afford treatment," the regional drinking water program chief said. "But if you have 100 people … treatment is very expensive."

The new standards for radium in tap water are anything more than 5 picocuries of radiation per liter, while 30 micrograms of uranium in a liter of water is the maximum level.

Higher levels of both radioactive elements would place Colorado residents at a higher risk for both kidney damage and cancer, the Post said.