Some Practical Questions

The following questions and answers may be of interest in explaining the background to some of the practical aspects of fluoridation to those unfamiliar with the topic.

Who is responsible for the Fluoridation of Drinking Water?

The various health authorities are ultimately responsible for the fluoridation of water supplies. However, as the overall functions of sourcing, treatment and distribution of water for drinking rest with the sanitary authorities (borough corporations, county councils and urban district councils), it has been the case from the outset that the latter bodies undertake fluoridation on an agency basis.

Is the Fluoride concentration in Drinking Water measured regularly?

Yes. Monthly fluoride measurements are made of fluoridated supplies by the regional health authorities in accordance with the requirements of the Health (Fluoridation of Water Supplies) Act,1960. However, many additional fluoride measurements are made by or on behalf of the sanitary authorities as part of their overall programmes of drinking water quality monitoring. The latter are in addition to any inplant checks which are more basic tests.

Who carries out any measurements made?

An increasing number of sanitary authorities have their own laboratory facilities, with appropriately qualified staffing and equipment, which undertake regular fluoride analysis complementary to the statutory monthly sampling carried out by the health authorities. However, most of the fluoride determinations are made by the three Regional Public Analysts, based in Cork, Dublin and Galway who operate under the auspices of the regional health authorities.

The Public Analysts' Laboratories are among the longest-established, best equipped and most experienced laboratories in the country and are ideally suited to the monitoring of fluoride on a national basis.

What becomes of the results of analysis?

First of all, the analytical results are sent from the laboratory to the health authority or sanitary authority which had the tests carried out. Should there be fluoride values which are either too high or too low (i.e. outside the range 0.8 - 1.0 milligrams/litre, (as required by the Health (Fluoridation of Water Supplies) Act,1960), notification will be sent to those responsible for the fluoridation of the supply in question, stating that adjustment of the dosage is required promptly.

Second, on completion of a calendar year's drinking water quality monitoring, each sanitary authority must return complete analytical data (for a range of parameters, including fluoride) to the Environmental Protection Agency which has the statutory function of preparing and publishing an annual report on the quality of drinking water in Ireland.

While the complete analytical data are not published in the EPA reports for practical reasons, there is complete reporting of each value for each parameter for each supply which is higher (by even the smallest amount) than the permitted limit. Thus the full details of all fluoride values in excess of the limit allowed are a matter of public record.

What controls are there on Fluoride levels in Drinking Water?

The permissible concentrations of fluoride in drinking waters are governed at both national and European Union level. Under the provisions of the Health (Fluoridation of Water Supplies) Act, 1960 the concentrations of fluoride in fluoridated public water supplies must be in the range 0.8-1.0 milligrams/litre. The National Drinking Water Regulations [2000] specify a so-called "parametric value" (previously termed "Maximum Admissible Concentration" or MAC for short) of 1.0 milligrams/litre in fluoridated supplies.

Why does the Health (Fluoridation of Water Supplies) Act, 1960 specify a lower as well as an upper limit?

As mentioned in the Introduction above, the whole purpose of fluoridation was to bring about a reduction in tooth decay. The research mentioned above also showed that there were no significant beneficial effects at a fluoride concentration below 0.8 milligrams/ litre.

On what is the 1.0 milligrams/litre upper limit based?

Ongoing research findings showed that at 1 milligram/litre a maximum reduction in dental decay occurred with only a small percentage of persons with dental fluorosis (staining of teeth). As levels of fluoride in water increased so did the occurrence of dental fluorosis of aesthetic concern. Indeed, when levels were consistently significantly greater than 1.0 (around double that value) the effects of fluoride were harmful rather than beneficial. Teeth became progressively more damaged as fluoride levels rose, starting with mottling or staining.

It should be noted that, under the December 2000 Drinking Water Regulations, the upper limit for supplies which are not fluoridated but which have naturally occurring fluoride present is 1.5 milligrams/litre.

Does a limit of 1.5 milligrams/litre of fluoride meet the EU Directive?

Yes. The December 2000 Drinking Water Regulations (which transpose the 1998 Drinking Water Directive into Irish Law) are in full conformity with the Directive. In both the original [1980] and successor [1998] Drinking Water Directives the limit for fluoride in drinking water in the EU is 1.5 milligrams/litre, without qualification.

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