Fluoride Vol. 32 No. 2 91-95 1999
Research Report
91
THE IMPACT OF WATER-BORNE FLUORIDE
ON BONE DENSITY
W Czarnowski,a J Krechniak,a B Urbańska,a K Stolarska,a
M Taraszewska-Czarnowska,b A Muraszko-Klaudelb
Gdańsk-Wrzeszcz, Poland
SUMMARY: The fluoride concentrations in drinking water, urine and hair
and the bone mineral densities (BMD) of 300 people (235 women, 65 men)
residing in the Gdańsk region, were determined. The mean water fluoride
level in the cities of Gdańsk, Gdynia, and Sopot was 0.32 mg/L; in Wiślinka,
a community located near a phosphate industry waste disposal site, it was
1.69 mg/L; and in the Żuławy area with a high fluoride content in the soil, it
was 2.74 mg/L. The mean fluoride concentrations in urine in the above mentioned localities were: 0.77 mg/L, 1.93 mg/L, and 2.89 mg/L, respectively; in
hair: 4.13 µg/g, 10.25 µg/g, and 14.51 µg/g, respectively. The mean values of
BMD in the femur bone were 0.92 - 1.05 g/cm2. High positive correlations
(P<0.001) were found between the fluoride concentrations in water and
urine, in water and hair, in urine and hair, in water and BMD, and in urine
and BMD. Negative correlations were found between age and BMD. The results of this study indicate that the fluoride level in water has an impact on
the fluoride levels in urine and hair as well as on bone mineral density.
Keywords: Age, Bone mineral density, Hair fluoride, Poland, Urine fluoride, Water fluoride.
INTRODUCTION
It is generally accepted that fluoride stimulates bone formation. 1,2 Fluoride
is incorporated into bones, where it replaces the hydroxyl ion in the crystal
lattice of apatite. However, the increase in bone mass from fluoride is to a
large extent the result of pathological bone formation resulting from injured
metabolically active bone cells. 3 Fluoride intake increases bone mineral density, but decreases the tensile strength and makes bones more fragile. 4,5 Fluoride
is still used in the therapy for different bone disorders. 6-8 However, recent
studies have shown that it should be avoided especially in treatment of osteoporosis.3
Excessive intake of fluoride may even lead to crippling skeletal fluorosis.9,10 One of the parameters used in diagnosing different osteopathies is the
assessment of bone mineral density (BMD).
The aim of this study was: (1) to dete rmine the fluoride levels in urine
and hair of people with known water fluoride intake and bone mineral density,
and (2) to assess whether a correlation exists between bone density and the
fluoride levels in drinking water, urine and hair.
MATERIALS AND METHODS
A total of 300 people (235 women, 65 men) aged 24 to 77 years (mean age
50 years) residing for at least 10 years in the Gdańsk region were examined.
Bone mineral densities of the left femur and vertebrae L 2-L4 were measured
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aFor Correspondence: J Krechniak, Department of Toxicology, Medical University of
Gdańsk, Al. Gen.Hallera 107, 80-416 Gdańsk-Wrzeszcz, Poland. bDepartment of Radiology, Medical University of Gdańsk.
92 Czarnowski, Krechniak, Urbańska, et al.
with a Lunar Expert densitometer in the Department of Radiology, Medical
University of Gdańsk.
Samples of urine and hair from the occipital part of the scalp were collected from the investigated subjects. Samples of drinking water were also gathered from every community where these people
lived (Figure 1).
The fluoride levels in
the samples of drinking
water and urine were determined directly using a
fluoride-specific electrode
after dilution with equal
volumes of TISAB buffer.11 The hair samples
were washed and digested
with concentrated sodium
hydroxide solution,12 and
the final determination of
fluoride content was determined as above.
Statistical analysis was
performed using Student’s t-test. Regression
equations and correlation
coefficients were calcuFigure 1. Locations of
lated with Microsoft Exsampling in the Gdańsk region.
cel 97, a spreadsheet program.
RESULTS AND DISCUSSION
The water fluoride level in the region investigated is very differentiated
(Table 1). In the Gdańsk metropolitan area (GMA) comprising the cities of
Gdańsk, Gdynia, and Sopot, the fluoride concentration in drinking water was
low, 0.32 mg/L. In Wiślinka, a community situated in the vicinity of a large
phosphate industry waste disposal site (which contains about 0.2% of soluble
fluoride compounds13), the fluoride level in the local water supplies was 1.69
mg/L. In all the localities situated in the Żuławy region (Cedry Wielkie, Suchy
Dąb, Kożliny, and Błotnik), the water fluoride level was even higher (mean
value 2.74 mg/L) due to high fluoride content in the soil.
The urine and hair fluoride concentrations in Wiślinka and the Żuławy region were significantly higher (Table 2) when compared to the levels determined in the GMA (Table 1).
The fluoride level in urine and hair depends mainly on the water fluoride
concentration.14,15 However, other sources (inhalation of air-borne fluoride
and the diet) also have an impact on the fluoride level in these media. 11,15
Fluoride 32 (2) 1999
Impact of water-borne fluoride on bone density
93
Table 1. Fluoride content in urine, water, hair and bone mineral density (BMD).
Localities
Mean F content
Wiślinka
Mean  S.D.
Żuławy
Mean  S.D.
GMA
Mean  S.D.
Total
N
Water mg F-/L
N=99
1.69  0.44
N=111
1.93  0.82
N=111
10.25  6.63
N=108
1.03  0.13
N=107
1.13  0.17
N=82
2.74  0.99
N=89
2.89  1.39
N=84
14.51  6.29
N=88
1.05  0.17
N=88
1.17  0.19
N=100
0.32  0.28
N=100
0.77  0.49
N=53
4.13  2.24
N=100
0.92  0.14
N=100
1.09  0.17
281
Urine mg F-/L
Hair g F-/g
BMD femur g/cm2
BMD vertebrae L2-L4 g/cm2
300
248
296
295
N = number of samples
GMA = Gdańsk metropolitan area (Gdańsk, Sopot and Gdynia)
Table 2. t-values
Comparison of
localities
GMA/Wiślinka
GMA/Żuławy
Wiślinka/Żuławy
Water
Urine
Hair
BMD
femur
BMD
L2-L4
26.34
P<0.001
21.41
P<0.001
12.74
P<0.001
13.76
P<0.001
8.71
P<0.001
13.85
P<0.001
5.56
P<0.001
5.87
P<0.001
1.79
P<0.1
3.54
P<0.001
5.96
P<0.01
5.78
P<0.001
4.58
P<0.001
1.25
P<0.3
1.99
P<0.05
The bone mineral density of the femur bone and vertebrae L 2-L4 was also
higher in localities with increased water fluoride, but the differences were not
always significant (Tables 1 and 2).
Correlations between various parameters investigated in this study are given in Table 3. The highest positive correlation (r = 0.722, P<0.001) was found
between the fluoride levels in water and urine. Also, there was a high positive
correlation (r = 0.425, P<0.001) between the fluoride levels in urine and hair
of the people investigated. The weakest positive correlation was found between the fluoride levels in hair and bone mineral density. As expected, a
negative correlation was observed between the age of the people and their
bone mineral density in the vertebrae and the femur bone.
The results of this study seem to indicate that increased fluoride intake affects the fluoride levels in urine and hair and also has an impact on bone density.
Fluoride 32 (2) 1999
94 Czarnowski, Krechniak, Urbańska, et al.
Table 3. Correlation coefficients
Comparison
Water/urine
Water/hair
Urine/hair
Water/femur BMD
Water/L2-L4 BMD
Urine/femur BMD
Urine/L2-L4 BMD
Hair/femur BMD
Hair/L2-L4 BMD
FemurBMD/L2-L4 BMD
Age/femur BMD
Age/L2-L4 BMD
N = number of samples;
N
r
282
249
248
299
299
281
282
250
249
298
297
296
0.722
0.240
0.425
0.241
0.198
0.310
0.210
0.190
0.120
0.674
-0.287
-0.292
r = correlation coefficients;
P
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.1
<0.001
<0.001
<0.001
P = probability.
The paper was presented at the XXIInd Conference of the International Society for Fluoride Research, Bellingham, Washington, USA, August 24-27,
1998.
ACKNOWLEDGEMENT
This study was supported by grants W-40 and W-56 from the Medical
University of Gdańsk.
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Fluoride 32 (2) 1999