Ene Indermitte, an environmental health researcher at the University of Tartu, has measured the level of fluoride in towns across the country since 2000. Water quality standards permit fluoride content up to 1.5 milligrams per liter. Even a small excess quantity can have negative health impacts, but the highest measurement discovered by Indermitte was a startling 6.95 milligrams per liter.

In areas with high fluoride contamination in drinking water, 80 percent of 12-year-olds showed signs of fluorosis, a condition caused by excessive exposure and marked by discoloration in teeth.

"Fluorosis of the teeth is a very serious illness; it causes permanent damage to the tooth’s enamel," said Indermitte. "In the beginning it’s just unattractive. [There are] ugly spots, tarnished teeth and stains. But micro-cracks emerge after a while and teeth can even fall out."

Emajõe Veevärk, a utility company based in Tartu County, serves 55 towns and villages with high-fluoride drinking water. A representative of the utility said the problems will be resolved by the end of the year at the latest.

“If it’s possible to drill a new artesian well into another water layer, where we can mix low fluoride content water with high fluoride content water, then it is a simple and inexpensive job,” said the company's director, Andres Aruhein.

On the other hand, fluoride-deficient water increases the likelihood of dental caries.

Mare Saag, director of the stomatology clinic at the University of Tartu, said that five years of data collection have shown that 40 percent of Estonia’s drinking water has a deficiency of fluoride.