[Tap water as a dietary source of exposure to fluoride in Tenerife; risk assessment]

drinking water is the main source of fluoride exposure for the population. According to the Spanish Law RD 140/2003, the fluoride content in drinking water should not exceed the parametric value of 1.5 mg/L. Historically, certain drinking waters in the island of Tenerife have exceeded this value due to the geological/volcanic characteristics of the Canary Islands. Fluoride (F) plays an important role in the prevention of dental caries (tooth decay). However, long exposure to concentrations above 1.5 mg/L in drinking water can cause disorders such as dental fluorosis.

To determine the amount of fluoride in the tap waters of the 11 municipalities in the north of the island of Tenerife that, at the time of the study, exceeded the parametric value for fluoride set by the Spanish legislation and to toxicologically estimate and evaluate the fluoride daily intakes from water considering the RDI (Recommended Daily Intake) established in Spain for different population groups.

44 samples of tap water collected in the 11 municipalities in the study were analyzed using the fluoride potentiometric determination with an ion selective electrode.

9 of the 11 municipalities presented mean fluoride concentrations in their tap water that exceeded the parametric value set by the Spanish legislation (1.5 mg/L). Considering an average daily water consumption of 2 L, the recommended daily intake (RDI) for women (3mg F/day) is exceeded in 9 of the 11 municipalities and the RDI for men (4 mg F/day) is exceeded in 5 of the 11 municipalities. Considering a daily water consumption of 1.5 L, the RDI for children of 2-3 years (0.7 mg/day) is clearly exceeded in all municipalities.

The results show the existing public health problem on the island of Tenerife and justify the tap water consumption restrictions put in force by the Public Health Authorities of the Canary Islands at the time of the study. Children are the most exposed population group to the risks of fluoride because its RDI is lower.