The quality of drinking water in England
and Wales has been summarised in the Drinking Water Inspectorate's (DWI) sixth
annual report. DWI [part of the Department of the Environment (DoE)] says that
99.5% of the 3.2 million tests (some of which are for pesticide residues),
carried out by water companies in 1995, complied with both national and European
Commission standards.
The number of individual pesticides monitored by each company
varies according to monitoring strategies. It is clear that not all pesticide
residues can be detected in drinking water. Certainly all companies have been
advised to monitor for the water soluble herbicides atrazine and simazine.
Overall during 1995, 32 pesticides were found above the
prescribed concentration value (PCV) of 0.1 µg/litre. For 24 of the 32 samples,
health based recommendations on maximum advisable concentrations or exposures
have been issued variously by the World Health Organisation, the UK Scientific
Committee on Pesticides, and the US Environmental Protection Agency. In all but
three cases (Trichloroacetic acid (TCA), chloro-toluron and DDT and
metabolites), the highest reported concentrations and corresponding exposures
were within the ranges considered acceptable by these authorities. DDT was
detected at concentrations of 6.6 µg/l and 12.2µg/litre total value (of DDT
isomers and metabolites). These are greater than the WHO guideline value (GV) of
2µg/litre for DDT (total isomers). The GV has been exceeded despite DDT having
been withdrawn from use in the UK since 1984.
The DWI found that 79.2% of water supply zones complied with
standards in the case of individual pesticides. The corresponding figure for
total pesticides was 91.2%.
Drinking Water 1995: A report by the Chief Inspector Drinking Water Inspectorate, DoE and Welsh Office, HMSO, Tel. (0)171 873 9090, Fax (0)171 873 8200, July 1996, £30.00, 221pp.
[This
article first appeared in Pesticides News No. 33, September 1996,
page 26]