§ Mr. Peter Robinson
To ask the Secretary of State for Northern Ireland (1) what levels of fluoride, in parts per million, have been added to the waters of Tandragee and Holywood for each month up to April 1996; 
(2) if he will list the quantities of aluminium added to the drinking water in Northern Ireland indicating the quantities added in each year since it was first added; 
(3) in what quantity aluminium is now added to the drinking water in Northern Ireland, given the figures by treatment plant. 
§ Mr. Moss
Responsibility for the subject in question has been delegated to the Water Service under its chief executive, Mr. H. R. F. Plester. I have asked him to arrange for a reply to be given.
Letter from H. R. F. Plester to Mr. Peter Robinson, dated 28 January 1997:
You recently put down three parliamentary questions about Water Service operational matters which have been passed to me for reply as its Chief Executive. I shall answer each in turn in this letter according to the order in which they were tabled.
To ask the Secretary of State for Northern Ireland what levels of fluoride, in parts per million, have been added to the waters of Tandragee and Holywood for each months up to April 1996.
The level fluoride added to the water put into public supply at Holywood and Tandragee is governed by the provisions of the following legislation:
the Water (Fluoridation) (Northern Ireland) Order 1987; and
the Water Quality Regulations (Northern Ireland) 1994.
Under the provisions of the Order fluoride levels are, so far as is reasonably practicable, to be maintained at one milligram per litre. The maximum limit permitted by the regulations is 1.5 milligrammes per litre. The water supplies at Holywood and Tandragee met the regulatory standards for the year prior to April 1996. Fluoridation takes place at the water treatment plants serving Holywood and Tandragee under arrangements with the health authorities which the Water Service inherited from the previous local authority water supply undertakers at local government reorganisation in 1973.
To ask the Secretary of State for Northern Ireland, if he will list the quantities of aluminium added to the drinking water in Northern Ireland indicating the quantities added in each year since it was first added.303W
Aluminium is not added to drinking water supplies. Various aluminium compounds are used at certain water treatment plants during the treatment of raw water supplies to make them fit to be put into the public supply. These compounds are used as coagulants to remove impurities from the raw water during the clarification phase of the treatment cycle. They are then removed by further treatment processes. Traces of these compounds may however pass into supply. Traces of naturally occurring aluminium which is abundant in many rocks and soils, such as those in the Mourne reservoir catchment, from which water supplies are derived may also pass into supply. Maximum permitted levels of aluminium for the public water supply are set by the Water Quality Regulations (Northern Ireland) 1994. These regulations, which incorporate EC and national controls and standards, set a standard of 200 microgrammes per litre, with a derogated level of 500 microgrammes per litre permitted for supplies derived from areas where aluminium is naturally occurring.
To ask the Secretary of State for Northern Ireland, in what quantity aluminium is now added to the drinking water in Northern Ireland, giving the figures by treatment plant.
As the previous reply indicates aluminium is not added to drinking water supplies. It may occur in water supplies as a trace element after raw water treatment by aluminium compounds during the clarification process, or because of natural aluminium levels in the geological strata from which a water supply is derived. Water Service's performance in respect of the level of aluminium in water supplies is recorded in the first Drinking Water Quality Report issued by the Water Service in June 1996. A copy of this is enclosed for your information. A second drinking water quality annual report is due to be published in June this year.
§ Mr. Robinson
To ask the Secretary of State for Northern Ireland what percentage of children in Northern Ireland currently have dental fluorosis. 
§ Mr. Moss
The information requested is not available. A 1993 survey of children's dental health showed that 34 per cent. of children in Northern Ireland had enamel opacities. There are a number of possible causes of such opacities and it is not possible to determine the proportion which are due to fluorosis.
§ Mr. Robinson
To ask the Secretary of State for Northern Ireland what estimates he has made of levels of dental fluorosis among children in Northern Ireland following fluoridation of the water supply.