1.3.1 Introduction

The Guidelines are concerned with the safety and aesthetic quality of drinking water for consumers. Drinking water does not need to be absolutely pure to be safe. Because water is such a good solvent, pure water containing nothing else is almost impossible to attain. What is required is that drinking water be safe to drink for people in most stages of normal life, including children over six months of age and the very old. It should contain no harmful concentrations of chemicals or pathogenic microorganisms, and ideally it should be aesthetically pleasing in regard to appearance, taste and odour.

The Guidelines are derived so as to take account of the needs of an individual through a normal lifetime, including changes in sensitivity that may occur between life stages. Those at greatest risk of waterborne disease are infants and young children, people who are debilitated or living under insanitary conditions, and the elderly. Sensitive sub-populations (including those who are severely immuno-compromised) should seek further medical advice.

A wide range of measurable characteristics, compounds or constituents can be found in water and may affect its quality. They fall into several categories:

• physical

• microbial

• chemical, including

  • inorganic chemicals

  • organic compounds

  • pesticides

• radiological.

Appearance, taste and odour are useful indicators of quality because they are generally the characteristics by which the public judges water quality. However, water that is turbid or coloured, or has an objectionable taste or odour, may not be unsafe to drink. Conversely, the absence of any unpleasant qualities does not guarantee that water is safe.

The safety of water in public health terms is determined by its microbial, physical, chemical and radiological quality; of these, microbial quality is usually the most important.