Fluorine the fierce element - F. Combine F with hydrogen and it forms hydrofluoric acid which is so strong it can eat through glass and has to be stored in plastic containers instead. Fluorine is fiercely reactive - it's related to chlorine and bromine but a much more violent element. Fluorine in a compound with one other element is a fluoride - in fact it's a handy rule that any chemical ending in 'ide' has two constituent elements - fluorides have F and one other element. Ditto for chlorides such as sodium chloride. Common salt - you put it on your spuds but it's made of two very dangerous elements - sodium, a soft metal that explodes into action in contact with water and a toxic green gas chlorine, that was used to gas soldiers in the trenches during WW1. Calcium fluoride on the other hand is the mineral fluorite and is found as highly colourful gemstones. Uranium Hexafluoride used for the enrichment of uranium for weapons is mainly responsible for the production of F on a commercial basis.
For sure the evidence is highly significant in a statistical sense that a modicum of fluoride in drinking water improves dental health - somewhere in the range 0.7 to 1.2 parts per million (or milligrams of fluorine per litre of water) is recommended by the US Public Health Service. In the Republic of Ireland the recommended range is 0.8 to 1.0 mg/l. The maximum allowed fluorine concentration for drinking water in Ireland is 1mg/l - the EU limit is 1.5 mg/l and the US EPA has a 4mg/l limit with a recommendation of 2 mg to States to avoid mottling of teeth. The benefit in terms of reduced tooth decay first came to light from the study of populations that had naturally high fluoride levels in the water. The economic impact is significant with something like 51 million lost school hours in the USA annually due to tooth decay and affecting the poorer children disproportionately. The rate of dental decay is significantly higher in Northern Ireland than in the Republic because they no longer add fluoride to their public supplies water. It is also quite clear that if you have more than 2 mg/l fluorine there is an increased tendency to cause mottling of teeth (fluorosis). If you go above 4 mg/l in the water supply and/or ingest more than 8 mg per day you may suffer from a particular type of bone brittleness. Similar caveats apply to lots of common elements if taken in excess or in particular compounds. For example aluminium is toxic at low and high pH values and causes dementia in dialysis patients if let straight into the blood stream. Similarly, sodium affects your blood pressure. Nitrogen is lethal within minutes if it's combined with carbon as CN i.e. cyanide and nitrate is a problem for small babies at high concentrations. But on the other hand nitrogen is essential for forming the proteins in your body - you can't live without it. Lots of medicines or drugs are good for you in small, prescribed doses but can kill you if you overdose. Fluoride is good for teeth and bones at low doses but bad for them at higher doses. The Irish Fluoridation Forum web site provides some interesting presentations made by pro and anti-fluoridation at http://www.fluoridationforum.ie/forum_reports3.htm. The vast majority of representations made to it were opposed to fluoridation (as would be expected). The scientific quality of the presentations opposing fluoridation seem quite poor, however, in the sense that the anti-fluoride statements are not backed by very strong scientific evidence - they are more anecdotal in nature not based on peer-reviewed science and tend to include lots of newspaper reports in the reference lists! (Citing newspapers as the source of supposedly scientific information drives scientists nuts - the ones that go to the trouble of producing peer-reviewed journal papers at least).
So what should you be asking about fluoridation of water supplies?
1. Is it ethical for the government to implement a policy that reduces the national level of tooth decay?
2. Are we sure that the local authorities are not exceeding the 1mg/l fluorine limits? According to the EPA's web site about 74 samples from a total of 22801 samples of Irish drinking water in the year 2000 exceeded this limit in the year 2000 (0.3% failure). You can check the Castlebar water supply, for example, by getting hold of the EPA's drinking water reports - www.epa.ie.
3. Are we happy that the chemicals used in the fluoridation process are not contaminated with other nasties like arsenic (again check out the EPA's report on your own particular water supply).
The other big use of fluorine is in the making of chlorofluorocarbons or CFCs responsible for the demise of the ozone layer. CFCs have been banned now for some time in your fridge and hairspray can but there are still a lot of older fridges with CFCs still pumping around and there is a suspicion that China is still producing them in vast quantities. A very sound scientific case was made and the result was the banning of CFCs. The system works?
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