Drinking water is, in most places, the primary source of F in the diet. Teeth and bones are particularly sensitive to aqueous F concentrations and 0.7 to 1 mg/L is estimated to be optimal to prevent dental caries in the developing teeth of children without causing dental fluorosis (Heller et al., 2007).
The World Health Organization (WHO) guideline value for fluoride in drinking water is 1.5 mg/L and this has been adopted as the national standard in most countries across the world, although higher limits are set in some countries with particular fluoride challenges (Table 1). As noted above, the US Environmental Protection Agency (EPA) has set the primary standard, the maximum contaminant level (MCL), for fluoride in US public drinking water at 4 mg/L, with the secondary standard at 2 mg/L. Tanzania adopted in the 1970s a temporary standard for fluoride in drinking water of 8 mg/L, which was reduced to 4 mg/L four decades later in 2014 (EWURA, 2014). China has adopted a national standard of 1 mg/L (Wen et al., 2013) as shown in Table 1.
|WHO||Guideline value (GV)||1.5||Fourth edition (2011) guidelines, as previous|
|US EPA||Maximum contaminant level guideline (MCL)||4||Enforceable regulation|
|US EPA||Secondary standard||2||Guideline intended to protect against dental fluorosis; not enforceable|
|US PHS||Recommendation||0.7||Recommended upper limit for fluoridation|
|EC||Maximum admissible concentration (MAC)||1.5||1998 regulations|
|India||National standard||1.5||‘Acceptable’ limit 1.0 mg/L|