Photo by Deb Gau In the photo, Jeff Larson, water operations manager at Marshall Municipal Utilities, demonstrates taking a sample of raw water for fluoride testing at the Marshall water treatment plant. MMU does add a small amount of fluoride to city water – but it’s also naturally present in the area’s groundwater, Larson said.

MARSHALL — A mineral commonly added to American drinking water was in the news this week. U.S. Health Secretary Robert F. Kennedy Jr. said he planned to tell the Centers for Disease Control and Prevention to stop recommending that communities fluoridate their water.

Recommendations about fluoride are something Marshall Municipal Utilities is keeping an eye on, MMU Water Operations Manager Jeff Larson said this week.

“We’re monitoring this so we know what’s going on,” Larson said.

But even if federal recommendations change, southwest Minnesota residents would likely still be getting fluoride in their water.

The mineral is naturally present in the region’s groundwater, Larson said.

On Wednesday, Larson explained how fluoridation works at MMU’s water treatment plant in Marshall. Current rules set by the Minnesota Department of Health say fluoride levels in city water should be between 0.5 and 0.9 parts per million, he said. Marshall city tap water consistently has fluoride levels in the middle of that range, at 0.7 parts per million, Larson said.

With the natural levels of fluoride in the groundwater in southwest Minnesota, “We’re at 0.4 (parts per million) already. So we add very little,” he said.

A spokesperson from the Minnesota Department of Health said Wednesday that fluoride can naturally be found in soil, fresh water and ocean water. Adjusting the natural levels of fluoride in water helps prevent tooth decay, and helps people save money on dental treatment costs, MDH said.

Minnesota laws require cities to fluoridate their municipal water supply, and keep the amount of fluoride in the water at a level set by the state health commissioner. Communities that naturally have enough fluoride in their water supply aren’t required to add more.

At the MMU water plant, a pump system injects the additional fluoride into city water during the treatment process. The amount of fluoride added to the water can be adjusted through the plant’s control room, Larson said.

Larson said MMU tests water samples for fluoride levels every day, using a machine called a spectrophotometer. The tests help MMU make day-to-day adjustments of fluoride levels, Larson said. Once a quarter, additional testing is conducted for the MDH.

The process of adding fluoride to public water systems in the U.S. began in 1945 in Grand Rapids, Michigan, according to a scientific statement on the CDC website. The CDC said evidence showed that community water fluoridation was an effective way to reduce tooth decay.

Although fluoride can help strengthen teeth, “Too much of it is known to be an issue, too,” Larson said.

In some parts of the world, high levels of fluoride in the groundwater are a problem that can cause conditions like discolored teeth or brittle bones, he said.

However, the MDH and CDC said scientific evidence showed that fluoridation of community water supplies in the U.S. was at a low enough level to be safe. The CDC’s website said documented risks of community water fluoridation were limited to dental fluorosis, a condition that can cause tooth discoloration.

The CDC said a review of available scientific evidence did not find “convincing evidence” linking fluoridated water and risks for adverse health effects like cancer, low intelligence, Alzheimer’s disease or allergic reactions.

CDC recommendations for water fluoridation are widely followed but not mandatory, the Associated Press reported Wednesday. State and local governments can decide whether to add fluoride to public water systems, and how much. They just can’t exceed the U.S. Environmental Protection Agency’s limit of 4 milligrams per liter.

This week, the EPA announced it would review new scientific information on potential health risks of fluoride in drinking water, the Associated Press reported.

Larson said MMU will be paying attention to news from federal agencies and the MDH, to stay informed of any changes in fluoridation rules in the future.