Fluoride
Naturally present in many groundwaters and added deliberately to some public supplies for dental health. Fluoride is unusual among water constituents in having a narrow band between beneficial and harmful intake, which is why both deficiency and excess are recognised public health problems.
Key facts
- Contaminant group
- Metal
- World Health Organization — guideline
- 1.5 mg/l
- European Union — legal limit
- 1.5 mg/l
- United Kingdom — legal limit
- 1.5 mg/lWhere fluoridation schemes operate, the target concentration is around 1 mg/l.
- United States — legal limit
- 4 mg/l enforceable; 2 mg/l secondaryThe recommended concentration for fluoridation schemes is 0.7 mg/l.
Where it comes from
- Natural dissolution from fluorine-bearing minerals, severe in parts of the East African Rift, India and China
- Deliberate fluoridation of public supplies
- Industrial discharge from aluminium and phosphate processing
How it behaves in water
Highly soluble and conservative in water. Concentrations in groundwater are set by geology and can exceed guideline values by an order of magnitude in affected regions.
How it is measured
Measured in milligrams per litre by ion-selective electrode or ion chromatography.
Regulatory position
| Jurisdiction | Value | Status | Notes |
|---|---|---|---|
| World Health Organization | 1.5 mg/l | guideline | — |
| European Union | 1.5 mg/l | legal limit | — |
| United Kingdom | 1.5 mg/l | legal limit | Where fluoridation schemes operate, the target concentration is around 1 mg/l. |
| United States | 4 mg/l enforceable; 2 mg/l secondary | legal limit | The recommended concentration for fluoridation schemes is 0.7 mg/l. |
Table sources
- World Health Organization — Guidelines for Drinking-water Quality. Public but restricted · CC BY-NC-SA 3.0 IGO
- European Commission — Drinking Water Directive (EU) 2020/2184 and reporting. Open — attribution required · European Commission reuse policy (Decision 2011/833/EU)
- Drinking Water Inspectorate — Drinking water quality in England and Wales. Open — attribution required · Open Government Licence v3.0
- United States Environmental Protection Agency — Safe Drinking Water Information System. Open · US Government work — public domain
Health context
At around 1 mg/l fluoride reduces dental caries. Above roughly 1.5 mg/l chronic intake causes dental fluorosis, and sustained exposure well above that causes skeletal fluorosis, a disabling bone disease affecting millions of people in high-fluoride regions. Water fluoridation is a policy question on which jurisdictions legitimately differ; the concentration-response relationship is not in serious dispute.
What removes it
| Row | Effective | Not reliably effective |
|---|---|---|
| 1 | Activated alumina adsorption | Boiling, which concentrates it |
| 2 | Bone char filtration, widely used in affected regions | Activated carbon |
| 3 | Reverse osmosis | Standard water softeners |
| 4 | Distillation | — |
| 5 | Nalgonda coagulation technique | — |
Relationships
Related intelligence
Sources
- World Health Organization — Guidelines for Drinking-water Quality. Public but restricted · CC BY-NC-SA 3.0 IGO
- Peer-reviewed scientific literature — Open-access hydrology, water chemistry and water use research. Public but restricted · Publisher terms — public access, reuse not clearly granted