Tests done on private wells in one-quarter of Maine towns found pockets of dangerously high fluoride levels, particularly in Hancock County.

While low levels of fluoride prevent tooth decay and promote oral hygiene, high fluoride levels, if unaddressed, have been found to cause pitted teeth and brittle bones. Some studies also have linked excessive fluoride levels to IQ deficits in children.

The survey, in which about 25 percent of all Maine towns participated, was reported by Scientific American magazine Wednesday. The results showed that Dedham in northern Hancock County had the highest percentage of wells that tested above state guidelines, at 37.8 percent. According to the Maine Center for Disease Control and Prevention, which conducted the tests, 37 private wells were tested in Dedham.

In fact, eight of the 10 towns that had dangerously high levels were in Hancock County. The cluster in Hancock County is likely attributable to a high level of granite in the area, which contains a lot of fluoride, according to Robert Marvinney, director of the Maine Geological Survey.

According to the magazine, the tests were done for homeowners who voluntarily submitted samples to the state for testing, and were not a random or complete sampling of private wells in Maine.

The tests were conducted between 2005 and 2009, according to the Maine CDC. The dangerously high levels were found to exceed levels recommended by the U.S. Environmental Protection Agency, and were similar to levels referenced in studies done in communities in China and Iran that linked high fluoride exposure to decreased IQ levels.

“The sort of levels we’re talking about that are high in China are the sort of levels we see in some private wells,” Andrew Smith, Maine state toxicologist, told the magazine.

Smith was on vacation and not available to answer questions Wednesday, according to Maine Department of Health and Human Services spokesman John Martins. But Martins said the data cited by Scientific American is part of a broader data set of tests conducted between 2001 and 2012. Martins also said there was an education effort conducted by the CDC after the results were compiled.

Fluoride in drinking water has been the subject of scrutiny for decades. Many Maine communities have been adding fluoride to their public water since the 1950s and 1960s, although recent federal guidelines have prompted some water districts to reduce their levels.

Maine calls for acceptable levels of fluoride of between 1 and 2 parts per million in public water. However, in 2011 the federal Centers for Disease Control concluded that 0.7 parts per million was sufficient.

But only about half of all Maine residents get their drinking water from municipal sources. The rest have private wells and the levels of fluoride – and other elements – in each varies greatly.

Mike Gelberg, who owns Air & Water Quality in Freeport, offers homeowners a variety of solutions to water-quality issues. He said high fluoride levels are not a problem he has encountered often, but said he’s not surprised.

“If you don’t test your water, you don’t know what’s there,” he said.

The Maine Center for Disease Control and Prevention, according to its website, recommends that owners test well water regularly to see how much fluoride exists. But there is no state requirement to do so, and Gelberg said most homeowners don’t.

“The only time people have their water tested is when they buy a house or if they get sick,” he said.

Additionally, Gelberg said, fluoride is not always included in a standard water test, although it is if consumers go through the state’s laboratory.

The well survey conducted by the Maine CDC tested approximately 11,000 wells, but only about 25 percent of all Maine towns participated. Of those 110 communities, only 10 showed levels that were considered dangerous.

“I’m certain the number of wells that have this problem is smaller than those that have high arsenic, but this reinforces the need for people to test their wells,” said Marvinney, the Maine Geological Survey director.

A town official in Dedham said Wednesday that she could not remember whether the town was ever alerted to the state’s test results. Attempts to reach the town’s code enforcement officer and first selectman Wednesday were unsuccessful.

Rep. Ralph Chapman, D-Brooksville, who represents some of the Hancock County towns where high levels of fluoride were found, said he was aware of high arsenic levels in his communities.

But fluoride?

“This is the first I’ve heard of it,” Chapman said.

Arsenic in well water has been well documented because excessive amounts can pose serious health risks, including cancer and blindness. A study released this year by scientists from Columbia University and the University of New Hampshire linked arsenic in private well water to lower intelligence levels in schoolchildren in six central Maine communities.

But while there has been a big public education effort around arsenic, that hasn’t been the case with fluoride.

Charlie Culbertson, a geochemist with the U.S. Geological Survey in Maine, said arsenic used to be under the radar, too, and predicted that fluoride could be a focus of the next public education campaign.

As for mitigation, commercially available filters, such as Brita, do not remove fluoride, according to Gelberg, who said the only effective solution is to install a reverse osmosis system, at a cost of $1,000 to $2,000.

“Reverse osmosis will give you the best water outside of distillation,” he said.

Gelberg equated reverse osmosis to putting water through plastic wrap using pressure.

“We don’t often put in mitigation systems for high fluoride,” he said.

Staff Writer Eric Russell can be contacted at 791-6344 or:

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Twitter: @PPHEricRussell