TROY — Despite residents receiving a notice last week about higher-than-expected fluoride levels in a well in the town’s water system, a Troy water department official said Monday that there’s no cause for alarm.

The well is not in use, according to Justin Frazier, superintendent of the Troy Water and Sewer Department.

One of the town’s five drinking wells tested positive for fluoride at a level of 3.3 milligrams per liter in December before dropping to 1.3 milligrams per liter in January, Frazier said.

According to the N.H. Department of Environmental Services, fluoride is part of the state’s bedrock and is beneficial at low concentrations, particularly in preventing cavities. At above 2 milligrams per liter, fluoride can stain teeth, and in concentrations above 4 milligrams per liter, it can deposit in bones and cause arthritis, according to the department.

Though the well — which is in Jaffrey on Route 124 — isn’t in use, state law requires municipalities to notify residents of any reading higher than 2 milligrams per liter, Frazier said.

The Environmental Protection Agency’s maximum allowable level for fluoride is 4 milligrams per liter.

The town sent a notice to water customers with their water bills last week, according to Frazier. Since there’s no hazard to the public, he explained, the department opted to send the notices with the quarterly water bill, rather than on its own. If the well posed a risk to customers, the department would have notified them right away, he said.

Troy’s four other wells either had undetectable levels of fluoride or much lower concentrations that pose no danger to the public, according to Frazier.

He said the department will test the well more frequently going forward. The state requires fluoride testing once a year, but when high levels are detected, testing must be done quarterly until the levels drop, Frazier said. At that point, the department can return to testing once a year.

​Liora Engel-Smith can be reached at 352-1234, extension 1439, or lsmith@keenesentinel.com. Follow her on Twitter at @LEngelSmithKS.