Report No DWI0765

Jan 1996

Chemical incidents affecting drinking water are often detected by their effect on taste and odour. Such incidents vary from contamination by man-made substances such as fuels and industrial chemicals to contamination by naturally occurring compounds such as those produced by various algae and micro-organisms. In addition, chemical treatment including disinfection of water, may transform raw water contaminants into ones which have undesirable taste and/or odour properties. For example, chlorophenols are formed when raw water containing trace amounts of phenols from natural or industrial sources, is chlorinated.

Although it may be natural for consumers to assume that drinking water with an unpleasant taste or smell is not safe to drink, there does not appear to be a direct relationship between taste and odour and effects on health. Some compounds are toxic at concentrations in water which do not produce any taste or odour, whereas chemicals such as chlorophenols are typically detected by taste and odour at concentrations well below those likely to result in any health effects. The toxicity of a compound depends on the duration of exposure and higher concentrations may be tolerated if exposure is only for a short period. Although for many chemicals the taste and odour thresholds are lower than the health-based guidance value, such organoleptic effects cannot be ignored because populations exposed to unpalatable water frequently report a higher incidence of symptoms such as headache, nausea and gastrointestinal upset when compared to unexposed populations.

This reference guide is intended for use in assessing the possible health effects of chemical incidents which affect the taste and odour of drinking water. It contains data summaries on 20 priority chemicals or groups of chemicals which are considered most likely to give rise to a taste and odour incident. The data summaries provide information on taste and odour thresholds and health effects associated with short-term exposure of up to 1 week. The priority chemicals were chosen on the basis of a review of incidents which have occurred in Europe and North America over the last 20 years and which have resulted in taste and odour effects. The introduction to the data summaries gives information about the background to the project and an explanation of the terms used in the data summaries.

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