Water department officials said that their latest testing of Dubuque's water supply shows normal fluoride levels, meaning that it is once again safe for all ages to drink.

The Dubuque Water Department announced on Wednesday, February 5, 2020, that it had detected higher levels of fluoride than expected. Normal concentrations are below 2.0 milligrams per liter, but their testing in the afternoon showed concentrations at 3.07 milligrams per liter.

However, as of 9:30 p.m., those concentrations were once again below 2.0 milligrams per liter, back into the safe for all ages category.

Levels above 2.0 milligrams per liter can lead to permanent brown staining or pitting of teeth after prolonged exposure, called dental fluorosis, according to officials. Those under the age of 9 are at risk for this condition, as it only affects developing teeth that have not yet erupted.

Even if children under the age of 9 had drunk the water during the time period that officials were suggesting they not do so on Wednesday evening, it is unlikely they would have sustained permanent damage with such limited exposure.

Fluoride is added to public drinking water supplies to help prevent cavities from developing in teeth.

Concentrations of fluoride were well below the Environmental Protection Agency's alert level of 4.0 milligrams per liter, which could cause an increased risk of bone disease. However, a concentration above 2.0 milligrams per liter requires notification of the public according to Iowa Department of Natural Resources guidelines.

Members of the public may contact Denise Blakeley Ihrig, Water Department Manager, or Brant Schueller, Water Distribution Manager, with the City of Dubuque Water Department, with questions at (563) 589-4291.