Drinking water fluoride concentrations and baseline prevalence of dental fluorosis among elementary school children on San Juan Island, Washington

Fluoridation of community drinking water has been deemed one of the most important public health achievements of the 20th century. However, excessive fluoride ingestion by young children can cause dental fluorosis and, rarely, skeletal fluorosis. The EPA Maximum Contaminant Level (MCL) for drinking water fluoride is 4 mg/L, and the American Dental Association recommends 0.7-1.2 mg/L for optimal caries prevention. The risk of fluorosis from drinking water may be compounded by fluoride from other sources. While dental fluorosis is common in the U.S. (prevalence of 35-60% in fluoridated areas and 20-45% in non-fluoridated areas), severe or moderately severe cases are rare.

Residents of San Juan Island (population 15,700) in Washington state obtain drinking water from community and private wells. Testing by county officials revealed naturally occurring fluoride levels up to several times the MCL (0.51-12.45 mg/L). Private wells have not been tested systematically.

The San Juan Fluorosis Project—a community-based collaboration between San Juan County Health & Community Services, Friday Harbor School District, and University of Washington—is screening for dental fluorosis and measuring fluoride in household water, focusing on children with recently erupted teeth (grades 2-3). Parents complete questionnaires about water filtration and their child's dental practices, including use of fluoride supplements, dentifrice, or mouthwash. Each child's estimated total fluoride exposure will be compared to findings of fluorosis screening (available June 2007). The results will be valuable for local water management authorities and healthcare providers and will inform the ongoing political discussion and controversy regarding fluoridation in Washington state.