Justice David Collins asks: ”Is the dosage set out in the regulations the dosage I get when I drink a litre of water?” (Fluoride opponents continue the fight, October 3). He has the crucial point, which is generally ignored by fluoridationists: dose is how much an individual has, and is determined both by how much is in the water, and how much of the water is drunk.

The dose an individual can have without harm depends on body weight, health, and intake from other sources. Toxic doses are much lower in a 10-kilogram child than a 90kg adult.

The chronic ingestion toxic limit (MRL) is exceeded by large numbers of children, compromised adults and Maori (who have higher dietary fluoride) in New Zealand.

The health risks of chronic overdose of fluoride has been clearly identified in the NRC review 2006. For the Ministry of Health to not be monitoring fluoride dosage at the individual level is irresponsible.

Planning to exempt artificially added fluoride in the water supplies from the Medicines Act sets a concerning precedent.

STAN LITRAS, dentist

Wallaceville

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