Future Regulatory Parameters Implications for the UK
Final Report for Phase 1

January 2001


As knowledge regarding drinking water contaminants increases, there may be a need to consider making changes to drinking water standards and regulations. This has been recognised in the revised Drinking Water Directive (98/83/EC) with the opportunity to make changes at intervals. It is important that the Drinking water Inspectorate is in a position to judge the possible changes and to assess the implications that these would have for the United Kingdom. There are many sources of influence but the primary influences for Europe are the revision of the WHO Guidelines for Drinking Water Quality, the USEPA and concerns expressed by member states. However, there are other sources of direct and indirect influence. The Drinking Water Inspectorate placed a contract with Metcalf and Eddy Limited in partnership with CREH and Owen Hydes OBE to provide an assessment of future regulatory trends and the scientific and technical justification for those trends. This report represents the finalisation of stage 1.

A comprehensive assessment of a wide range of international sources of information was made and knowledge of the scientific and technical developments surrounding specific contaminants was used to indicate the priorities that could be applied to the substances and organisms of interest. It was recognised that priorities may change with new scientific data. Priorities may also change in response to changes in public perception and public and political concerns.

Microbial contamination remains the primary public health threat and drinking water standards have largely concentrated on the use of indicator parameters. However, the high priority organism for consideration as a possible future regulatory parameter was identified as Legionella, since one member state has already set a standard while others have expressed concerns. Medium priority organisms included Aeromonas, which grows in distribution and plumbing systems, bacteriophage, which has been discussed as a possible indicator for viruses, and Clostridium perfringens, which is already included in the directive but as an indicator parameter.

There is a high political and public perception that chemical contaminants in drinking water are of high importance, even when the scientific data do not support this. The chemical parameters considered to be of high priority were tri and tetrachloroethene, which are groundwater contaminants and which have been reassessed with regard to their carcinogenic risk, haloacetic acids, which are chlorination by-products, chlorite, which is a breakdown product of the disinfectant chlorine dioxide, uranium, which is naturally occurring in many waters, radon, which also occurs in some groundwater, aluminium and endocrine disrupters, which are both of high political and public concern in member states. A further 8 parameters were considered to be of medium priority but will depend on the availability of new data or changes in their public profile.

Recommendations for possible research were also made in order to address gaps in the scientific database.

Copies of this report may be available as an Acrobat pdf download under the 'Find Completed Research' heading on the DWI website.