Determination of Fluoride in Drinking Water

Report
Dieterich, M.F., Gieseler, M.E., Short, D.B., and Signorelli, R.T.
Abstract
Discussion
Fluoride occurs naturally in most water supplies and may be added in larger
concentrations above the natural background in order to promote dental
health. High levels of fluoride are known to cause health problems. Fluoride
concentrations in municipal water supplies were measured using an ionselective electrode. Fluoride was detected in 23 of the 25 samples collected,
all sites reported a concentration well below EPA’s standard of 4 ppm and the
WHO’s standard of 1.5 ppm.
The average fluoride concentration measured for all 25 samples was 0.57 ± 0.04
ppm. Results were as expected for all 25 samples who fluoridated their drinking
water with all concentrations measuring around 1 ppm fluoride. Fluoride
concentrations at or below 0.2 ppm seem to indicate water sources that were not
fluoridated.
Fluoride concentrations recorded below 0.1 ppm were below the level of detection
of our equipment. The results of this study were outputted using a Geographic
Information System (GIS) which maps the fluoride concentration of a ZIP code
area (figure 2).
Introduction
Since 1940, fluoride has been added to most public water supplies in the
United States to prevent dental caries and to aid children’s growing teeth [1].
Recent studies indicate that drinking waters containing fluoride concentrations
greater than 2 ppm may cause dental fluorosis (darkening of the teeth).
Drinking waters with fluoride concentrations containing greater than 4 ppm
may cause skeletal damage, with the most severe symptom being
osteosarcoma [1]. Data from the Harvard Fluoride Osteosarcoma Study
indicates that children between the ages of six and eight, exposed to high
fluoride concentrations, are at the highest risk of developing osteosarcoma
later in life [2].
Fluoride concentrations in natural waters vary between 0.05 and 3 ppm [4]. In
1986, the U.S. Environmental Protection Agency (EPA) established a
Maximum Contaminant Level Goal (MGLG) of 4 ppm and a Secondary
Contaminant Level (SCL) of 2 ppm for fluoride in drinking water [3]. The world
health organization (WHO) standard for fluoride is 1.5 ppm [5]. The target level
for fluoridation of drinking water is between 0.72 ppm and 1.2 ppm.
Growing concerns over fluoride related health issues have led many scholars
to request the termination of fluoridated drinking water. This study examines
fluoride in local water drinking supplies for comparison with national and world
acceptable concentrations.
Field Sampling
Water samples were collected at 25 sites in western Pennsylvania and
northern Maryland located at various zip codes (see Figure 2). Samples were
collected using 250 mL plastic bottles and preserved in a refrigerator at 4°C.
Method
A Thermo Fisher Scientific AR50 with ORION Fluoride ion selective electrode
(ISE) (figure 1) was used to measure fluoride concentrations in all collected
water samples. The ion selective electrode was calibrated daily with fresh
standards containing three different fluoride standards. An ionic strength
adjuster was added to all standards and samples to eliminate ionic
interferences from host solutions. Samples were measured in triplicate and a
mean value was reported.
Our data set is neither comprehensive or representative, and should be expanded
to include more ZIP code areas, as well as more samples per ZIP code. It would
also be desirable to determine if the lowest measured fluoride concentrations (0.2
ppm) represent a background level for natural fluoride.
Figure 1: Accumet AR50 with Orion Fluoride ISE.
Results
Location (ZIP)
F- (ppm)
SD
RSD
15205
0.65
0.006
0.96
15001
0.25
0.005
1.83
15001
0.14
0.002
1.28
15106
0.65
0.007
1.07
15009
0.17
0.009
5.20
15026
0.20
0.001
0.29
15108
0.77
0.001
0.08
15108
0.71
0.007
1.02
15108
0.10
0.003
3.33
15367
0.78
0.015
1.87
15522
0.21
0.001
0.28
21704
0.67
0.003
0.48
21117
0.77
0.011
1.42
21773
0.07
-
-
21740
-
-
-
17267
0.21
0.003
1.63
15533
-
-
-
15501
0.88
0.008
0.96
15063
0.75
0.011
1.51
15090
0.69
0.001
0.08
15227
1.02
0.023
2.26
15044
0.97
0.000
0.00
15209
0.19
0.003
1.36
15239
1.24
0.000
0.00
15063
0.95
-
-
Table 1: Fluoride concentrations by ZIP code.
All samples collected spring of 2012.
Figure 2: Map of sampling sites.
References
[1] Hauser, B.A. (2002). Dinking Water Chemistry: A Laboratory Manual.Boca
Raton, FL: CRC Press.
[2] Bassin, E.B., Wypij, D., Davis, R.B., Mittleman, M.A. (2006). Age-Specific
Flouride Exposure in Drinking Water and Osteosarcoma (United States). Cancer
Causes & Control, 17(4), 421-428.
[3] Artiola, J.F., Pepper, I.L., and Brusseau, M. (2004) Environmental Monitoring
and Characterization. Elsevier, Amsterdam.
[4] National Research Council. (2006). Flouride In Drinking Water: A Scientific
Review of EPA’s Standards. Washington, D.C.: The national Academics Press.
[5] Fawwell, J., Bailey, K., Chilton, J., Dahi, E., Fewtrell, L., and Magara, Y. (2006)
Fluoride in drinking-water. WHO.

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