Research programme

The objective of the Drinking Water Quality and Health Evidence programme is to provide the science base for policy on drinking water quality encompassing both health and consumer acceptability issues. The provision of an adequate supply of water that is safe to drink is a fundamental human requirement. The supply should also be aesthetically acceptable to consumers. Our current Drinking Water Quality and Health Evidence Plan (PDF 90.1KB) lays out the aims and objectives of the our research programme.

The adequacy of current levels of health protection is under continuous review and the decisions of the World Health Organisation (WHO), which sets global drinking water quality and health guideline values, are an important element in updating and revising the DWD. Future regulatory proposals may arise for chemical, microbiological and aesthetic parameters and so DWI must keep abreast of all these areas.

The programme as a whole, includes work to support the approval process for chemical and products in contact with drinking water and projects aimed at better understanding the best practice in drinking in water regulation, and also assesses risks to health in relation to emerging issues,and rapid methods of analysis to be deployed in the event of a threat to drinking water quality.


Current Research

Information on our part of our research programme, giving the description, objectives, contractors and costings can be found on the Defra science and research project database: under the theme Drinking Water Quality and Health.

Other ongoing new work includes:
Chlorate research project WT2209 - to be undertaken by Cranfield University

The aim of this project is to establish what current concentrations of chlorate are in drinking water supplied in England and Wales and any implications should a new health based value to be established.

Chlorate is a disinfection by product that can arise during the water treatment process where sodium hypochlorite, chlorine dioxide or onsite electrolytic chlorination (OSEC) is used for disinfection purposes.

Water companies have a regulatory duty to minimise disinfection by-products, however currently there is no prescribed concentration or value (PCV) for chlorate in drinking water. Consequently there is no routine regulatory monitoring for this species and as such limited data is held by the Drinking Water Inspectorate (DWI) on the concentrations found in public supplies. DWI has identified this as a gap in its knowledge.

Controls on chlorate are in place through national conditions of use for OSEC and chlorine dioxide and purity requirement under the BSEN for sodium hypochlorite. These should ensure that the World Health Organisation (WHO) provisional guideline value for chlorate (0.7mg/L) is not exceeded.

A recent Joint FAO/WHO Expert Committee on Food Additives (JECFA) committee has proposed an a acceptable daily intake (ADI) of 10 µg/kg bw for chlorate, and using standard assumptions, this would correspond to a health-based value of about 0.2 mg/L, which is below the current WHO provisional guideline of 0.7 mg/l. In addition, by extrapolation from perchlorate, EFSA has used a TDI of 3 µg/kg bw. This would correspond to an even more stringent value for drinking water.

The project will provide evidence of the current levels of chlorate arising from hypochlorite, chlorine dioxide and OSEC in England and Wales. It will also provide an understanding of the possible impact on disinfection practices, should a tighter health based value be adopted.


Page reviewed: 3 May 2017
Page modified: 3 May 2017

Drinking Water Inspectorate