Civil Engineering Reference
In-Depth Information
FLUORIDATION STANDARDS AND RECOMMENDATIONS
From the relationship between dental caries and fluoride concentration, the recom-
mended fluoride concentrations shown in Table 20-1 were determined.
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The recom-
mended fluoride concentrations decrease with increasing temperature because of the
hypothesis that more water is consumed during warm-weather periods than at cooler
temperatures.
Maximum fluoride levels in drinking water are regulated under Section 1412 of the
Safe Drinking Water Act (SDWA). When regulating a contaminant under this Act,
EPA promulgates both a Maximum Contaminant Level Goal (MCLG, a nonenforceable
health goal), and a Maximum Contaminant Level (MCL, which is a federally enforce-
able standard). The MCL is set as close to the MCLG as technically feasible, taking
costs and other factors into consideration. When establishing an MCLG, the Act re-
quires EPA to protect against adverse health effects with a margin of safety. The SDWA
leaves the question of what constitutes an adverse health effect to the EPA.
EPA may also promulgate nonenforceable secondary standards that are designed to
protect the public welfare. Secondary standards are usually based on aesthetic consid-
erations such as taste or odor.
In 1986, EPA promulgated both the fluoride MCLG and MCL at 4 mg / L. This
level protects humans from crippling skeletal fluorosis, an adverse health effect.
At the same time, EPA also set a nonenforceable Secondary Maximum Contaminant
Level of 2 mg / L for fluoride in drinking water to protect against objectionable dental
fluorosis (i.e., a staining and / or pitting of the teeth). While community water systems
are not required to reduce the level of fluoride if it exceeds 2 mg / L, they are required
to distribute a public notice which advises that children are likely to develop objec-
tionable dental fluorosis. In developing the MCL and the MCLG at 4 mg / L (vs. 2 mg/
L to protect against dental fluorosis), EPA concluded that dental fluorosis is a cosmetic
effect and not an adverse health effect.
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FLUORIDATION
Fluorine is the most chemically active element known. Like chlorine, it is always found
in the reduced state (F
) in combination with other elements. In water solution, the
TABLE 20-1. Recommended Limits for Fluoride in Drinking Water
Annual Average of Maximum Daily Air
Temperature,
F(
C) Based on
Temperature Data Obtained for a
Minimum of 5 Years
Recommended Limits, mg / L
Lower
Optimum
Upper
50-54 (10-12)
0.9
1.2
1.7
54-58 (12-15)
0.8
1.1
1.5
58-64 (15-18)
0.8
1.0
1.3
64-71 (18-21)
0.7
0.9
1.2
71-79 (21-26)
0.7
0.8
1.0
79-91 (26-33)
0.6
0.7
0.8
Source:
Reference 9.
