Fluoride is naturally present in all water supplies at varying levels.
Some water supplies contain fluoride naturally, for instance where water is taken from an underground source where the water has passed through rocks with fluoride containing minerals in them. The natural background level of most source waters in the UK is below 1 part per million (mg/l).
Some water companies, at the instruction of health authorities, add fluoride to the water to help tackle tooth decay. We do not artificially fluoridate any of our water.