BFS briefing on opponents’ claims that silica and other contaminants are added to water supplies in the process of fluoridation that are not ordinarily present in non-fluoridated water.

 

SILICA

 

·         Section 2 (page 5) of the July 2002 WRc report Chemistry and Bioavailability Aspects of Fluoride In Drinking Water explains that when hexafluorosilicic acid is dosed into water it dissociates to form fluoride ion (F–) and silicic acid (Si(OH)4)

·         The silicic acid (Si(OH)4) will itself dissociate into silica (silicon dioxide) and water: Si(OH)4 D SiO2 + 2H2O

·         The familiar forms of silica are quartz or sand, and is usually considered inert.

·         Silicon/silicate determinations are not required by the European or UK Drinking Water Quality Regulations, and are not routinely measured by water companies. However, in common with other constituents of water, concentrations naturally vary across the UK.

·         Neal et al (2005) described the variations in silicon concentrations in UK waters for a wide range of catchment systems and attribute clear variations to “two primary processes (1) the relative inputs of groundwaters enriched in silicon and near surface waters more depleted in silicon and (2) plankton uptake of silicon during the summer months under baseflow conditions.”

·         They concluded “Surface water silicon concentrations are variable across the UK but cover a relatively small range of 0–19 mg-Si litres -1.”

·         There are no health, or other adverse implications, for the consumer of the “residual” silica in fluoridated water since the silica is both indigestible and biologically inactive Indeed, silica is frequently used as a food additive, primarily as a flow agent in powdered foods, or to absorb water.

 

OTHER CONTAMINANTS

Citing the Fluorosilicic Acid Information Pack provided by Yara Industrial (the main supplier in the UK of fluorosilicic acid for fluoridation of drinking water supplies), opponents argue that fluoridated water contains silicates and contaminants, for example arsenic, that would not normally be present in non-fluoridated water.  They are wrong; the Trace Elements in question are all found in all water supplies, whether fluoridated or not.  Indeed non-fluoridated supplies often contain higher concentrations than do fluoridated.

Yara’s Fluorosilicic Acid Information Pack states that fluorosilicic acid is derived from a naturally occurring mineral, Apatite, and as such contains a number of Trace Elements which it lists.  There are standards for over fifty parameters that are monitored to determine the microbiological, chemical and aesthetic qualities of drinking water. These standards are outlined in legislation to protect public health, and compliance with these standards is monitored by the Drinking Water Inspectorate.  Companies report the range of results (Minimum, Mean, and Maximum) of a number of samples taken over a specific time period.

The tables below list, for two fluoridated and four non- fluoridated supplies, the permitted concentrations, the fluoride concentrations, and the mean (Table 1) and maximum (Table 2) concentrations of the Trace Elements listed by Yara. They demonstrate clearly that there is no association between the concentration of the Trace Elements and water fluoridation.  

 

Table 1. Mean concentrations (mg/l) of fluoride, and the Trace Elements listed on Yara’s Fluorosilicic Acid Information Pack, for fluoridated Solihull and Birmingham, and non fluoridated Bolton, Leeds, London and Croydon (information accessed from water companies websites 10 March 2009)

 

 

Permitted Concentration1

Solihull 2 (Fluoridated)

 

Birmingham2

(Fluoridated)

Bolton 3

(Non-fluoridated)

Leeds 4

(Non-fluoridated)

London 5

(Non-fluoridated)

Croydon5

(Non-fluoridated)

Antimony

5

<0.120

<0.120

0.103

<0.322

<0.5

<0.5

Arsenic

10

<0.370

<0.370

0.241

<0.258

<1.1

<1.0

Cadmium

5

<0.061

<0.060

<0.035

<0.044

<0.5

<0.5

Chromium

50

<0.700

<0.700

<0.264

<0.206

<5.5

<5.6

Lead

25

<1.71

<1.813

<1.05

<1.77

<2.7

<1.9

Mercury

1

<0.012

<0.012

<0.026

<0.022

<0.05

<0.05

Nickel

20

<1.163

<1.100

<1.02

2.406

<2.0

<3.0

Selenium

10

<0.220

<0.220

<0.325

<0.373

0.7

0.9

Fluoride

1500

930

900

<30

88

160

140

 

Table 2 . Maximum concentrations (mg/l) of fluoride, and the Trace Elements listed on Yara’s Fluorosilicic Acid Information Pack, for fluoridated Solihull and Birmingham, and non fluoridated Bolton, Leeds, London and Croydon (information accessed from water companies websites 10 March 2009)

 

 

Permitted Concentration1

Solihull2 (Fluoridated)

 

Birmingham2

(Fluoridated)

Bolton3

(Non-fluoridated)

Leeds4

(Non-fluoridated)

London5

(Non-fluoridated)

Croydon5

(Non-fluoridated)

Antimony

5

<0.120

<0.120

0.130

0.64

<0.5

<0.5

Arsenic

10

<0.370

<0.370

0.320

0.49

1.4

1.5

Cadmium

5

0.070

<0.060

<0.040

0.084

<0.5

<0.5

Chromium

50

<0.70

<0.700

<0.540

0.37

9.0

10.0

Lead

25

6.7

11.0

3.19

11.0

16.7

13.3

Mercury

1

<0.012

<0.012

0.068

0.46

<0.05

<0.05

Nickel

20

1.70

2.500

3.40

6.37

<2.0

10.0

Selenium

10

<0.220

<0.220

0.510

0.59

1.0

1.3

Fluoride

1500

1120

1000

30

120

194

190

 

------------------------------

British Fluoridation Society

12 March 2009

 

 


1 Maximum concentration permitted under EU and UK water quality legislation.