Worldwide there are thousands of fluoridation schemes in operation - the earliest dating from 1945. Water suppliers have therefore accumulated a wealth of practical experience in managing the fluoridation process safely and efficiently.

In the UK strict operational criteria are laid down in the Department of the Environment Code of Practice on Technical Aspects of Fluoridation of Water Supplies (Department of the Environment 1987). These are designed to ensure that:

• the mean fluoride content of the water leaving the works in a calendar month is maintained between 0.9 and 1.1 parts per million, calculated for those periods when the fluoridation plant is in operation;

• the fluoride content of the water leaving the works is maintained between 0.8 and 1.2 parts per million for at least 90% of the time when the fluoridation plant is in operation;

• the fluoride content of the water leaving the works shall not exceed 1.5 parts per million at any time.