The contribution of drinking water fluoride to the risk of dental fluorosis in Estonia

Fluoride is one of the few chemicals of natural origin that have been shown to cause significant health effects in people through drinking-water. The association between the fluoride level in drinking water and the degree of dental fluorosis has been documented worldwide. The permissible maximum health-based fluoride limit in drinking water is 1.5 mg/l. The aim of this paper is to assess human exposure to drinking water fluoride in Estonia and determine the contribution of drinking water fluoride content to the dental fluorosis risk. The paper is based on the survey of drinking water supply in Estonia drawn from the database of the National Health Protection Inspectorate and supplemented by a special study to determine the fluoride content of water in public water supplies all over Estonia. The retrospective case study to determine the risk of fluorosis was carried out. The subjects of the study were 12 years old, living in six districts of the town of Tartu with different fluoride content in drinking water. In total 368 children were investigated. Fluoride content in the drinking water of the Estonian population varied in a large scale. The permissible maximum limit was exceeded in 14.4% of water samples. High levels of fluoride are due to a natural geogenic source. The proportion of the population exposed to a high fluoride level in drinking water was small (4.2%), mainly consumers of small water supply systems in West-Estonia, where the only drinking water source is the Silurian-Ordovician aquifer system. Association between prevalence of dental fluorosis among 12-year old schoolchildren and fluoride content in drinking water was observed. The obtained data allowed the assessment of the risk of dental fluorosis for the Estonian population. Control of drinking water quality is critical in preventing fluorosis.