Linda Vail, the Ingham County health officer, has warned county employees in Mason that using tap water from the Mason municipal water system may pose a health hazard because of elevated copper levels.

“Recent water testing found elevated copper levels in a number of buildings, including county facilities, in the City of Mason,” Vail emailed all county employees on Friday. “Copper enters drinking water primarily through the corrosion of plumbing materials. To address this, the city has recently added additional anticorrosive (phosphate) to its water.”

High levels of copper can cause liver and kidney damage, anemia, immunotoxicity, and developmental toxicity, according to the CDC. Amanda Darche, a spokesperson for the ICHD, said the copper levels were unlikely to be high enough to cause those effect. She said it was possible, although most unlikely, that some people might have some stomach issues.

While the copper levels were not expected to cause health issues, Vail is warning employees to flush their lines before using the water and to use only cold water for drinking and cooking purposes.

Followup testing is expected in three to four weeks.

This story has been updated with a quote from Amanda Darche, spokesperson for the ICHD.