A Quantitative Look at Fluorosis, Fluoride Exposure, and Intake in Children Using a Health Risk Assessment Approach

Article excerpt

The prevalence of dental fluorosis in the United States has increased during the last 30 years. In this study, we used a mathematical model commonly employed by the U.S. Environmental Protection Agency to estimate average daily intake of fluoride via all applicable exposure pathways contributing to fluorosis risk for infants and children living in hypothetical fluoridated and nonfluoridated communities. We also estimated hazard quotients for each exposure pathway and hazard indices for exposure conditions representative of central tendency exposure (CTE) and reasonable maximum exposure (RME) conditions. The exposure pathways considered were uptake of fluoride via fluoridated drinking water, beverages, cow's milk, foods, and fluoride supplements for both age groups. Additionally, consumption of infant formula for infants and inadvertent swallowing of toothpaste while brushing and incidental ingestion of soil for children were also considered. The cumulative daily fluoride intake in fluoridated areas was estimated as 0.20 and 0.11 mg/kg-day for RME and CTE scenarios, respectively, for infants. On the other hand, the RME and CTE estimates for children were 0.23 and 0.06 mg/kg-day, respectively. In areas where municipal water is not fluoridated, our RME and CTE estimates for cumulative daily average intake were, respectively, 0.11 and 0.08 mg/kg-day for infants and 0.21 and 0.06 mg/kg-day for children. Our theoretical estimates are in good agreement with measurement-based estimates reported in the literature. Although CTE estimates were within the optimum range for dental caries prevention, the RME estimates were above the upper tolerable intake limit. This suggests that some children may be at risk for fluorosis. Key words: children, exposure, fluoride, multipathway, risk. doi:10.1289/ehp.7077 available via http://dx.doi.org/[Online 14 September 2004]

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Nearly two-thirds of the U.S. population receives drinking water from municipalities that add fluoride to their water systems to prevent dental caries [Centers for Disease Control and Prevention (CDC) 2002]. The CDC hails fluoridation of drinking water as one of the 10 great public health achievements of the 20th century (CDC 1999). The first Surgeon General's report on oral health in the United States credits fluoridation for dramatically lowering caries rates. Several studies have shown caries reduction of up to 60% after fluoridation [U.S. Department of Health and Human Services (DHHS) 2000a].

Although the efficacy of drinking-water fluoridation is well accepted by the scientific community and policy makers, the benefits are not without consequence. Ingestion of fluoride during the formative years of a child's enamel development can cause dental fluorosis--a condition marked by permanent, often pronounced staining of adult teeth. Reports of fluorosis prevalence in North American children range widely depending on public water fluoridation status (Clark 1994; Mascarenhas 2000; Riordan and Banks 1991; Tabari et al. 2000). In the National Survey of Dental Caries in U.S. school children (1986-1987), 22% of children examined had fluorosis (Brunelle 1989). In 1998, 69% of children 7-11 years of age examined in a suburban Boston pediatric practice were found to have fluorosis (Morgan et al. 1998). Children from a fluoridated community in North Carolina showed a prevalence of 78% with fluorosis (Lalumandier and Rozier 1995). In nonfluoridated communities, fluorosis prevalence reported in a number of studies conducted during 1990-2000 ranged from 3 to 45% (Clark 1994; Mascarenhas 2000; Riordan and Banks 1991; Tabari et al. 2000).

Several studies point to other sources of fluoride besides fluoridated drinking water (e.g., fluoride toothpaste, fluoride supplements, infant formula and beverages produced with fluoridated water, food grown in soil containing fluoride or irrigated with fluoridated water, and cow's milk from livestock raised on fluoride-containing water and Iced, and soil) that contribute to overall fluoride intake and therefore may contribute to dental fluorosis (Fomon et al. …