ST. PETER — Minnesota state officials are concerned about the minimal requirements for private well owners to monitor the safety of their drinking water.

Arsenic contamination is an emerging concern, Chris Elvrum with the state health department told Minnesota Public Radio. About 10 percent of wells in the state have unsafe amounts of arsenic, which occurs naturally in rocks and soil and can dissolve into groundwater, he said. The long-term risk of drinking the contaminated water is cancer, Elvrum said.

About a fifth of the state’s drinking water is from private wells. Many of the older wells have never been checked and newer wells often aren’t monitored after an initial sample is drawn, Elvrum said.

He recommends owners test their wells every one to two years for bacteria and nitrate, and at least once a year for arsenic. Certified laboratories can test samples sent by mail for around $50.

Bryan Buffington spent about $200 to install a reverse-osmosis system that removes nitrate contamination from his drinking water at his home near St. Peter.

Though he has to purchase filters every six months, the extra bill is worth the peace of mind that the water is safe for him and his family, the 52-year-old said.

David Henrich, president-elect of the National Ground Water Association board, said he believes few well owners test their water.

“People take for granted that the water comes out of the faucet, goes into the glass, they drink it, and that’s good enough for them,” said Henrich. “They don’t spend enough time on proper maintenance. And I would say there’s a lack of testing.”