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Drinking Water

Volume 175: debated on Thursday 5 July 1990

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To ask the Secretary of State for the Environment if he will make a statement on the incidence and levels of (a) tetrachloroethylene, (b) trichloroethylene and (c) polycyclic aromatic hydrocarbons in drinking water; if the levels detected have in any case exceeded World Health Organisation guidelines; and if he will discuss with his European Community counterparts the establishment of maximum advisable concentrations in respect of each of these chemicals.

The Water Supply (Water Quality) Regulations 1989 set standards for tetrachloroethylene and trichloroethylene of 10 and 30 microgram/litre respectively as annual averages. These are based on tentative guideline values promulgated by the World Health Organisation. No specific standards for tetrachloroethylene and trichloroethylene are laid down in the EC drinking water directive.Comprehensive information about the current incidence and levels of tetrachloroethylene and trichloroethylene in drinking water is not, at present, held centrally. The drinking water inspectorate is aware of a few public supplies which exceed the standards for these substances. The water companies concerned have either taken the supplies out of service or have given undertakings under section 20 of the Water Act 1989 to introduce treatment by 1994 in order to reduce the levels. Because of the safety margins allowed, medical advice is that public health is not endangered by those supplies which are continuing in use.The Water Quality Regulations incorporate the standard of 0.2 microgram/litre for six specified polycyclic aromatic hydrocarbons (PAH) laid down in the EC directive. They also set a national standard, based on the WHO guideline value, of 0.01 microgram/litre as an annual average for benzpyrene, an individual PAH.At the request of my Department and the Welsh Office water undertakers carried out a comprehensive survey of their supplies in early 1989 to establish levels of PAH in drinking water. Of approximately 6,250 samples,44—0.7 per cent.—contained concentrations in excess of standards mentioned above. These results indicate that there is not a general problem with PAH in drinking water. Where a high concentration of PAH is confirmed water companies carry out remedial programmes comprising relining or replacing water mains or flushing.I see no need at present for any additional EC standards for these substances.