ABSTRACT
The requirement to set a standard arises from a recognition or suspicion that one or more substances, when present in the environment in sufficiently high levels, will have undesirable, adverse effects of some kind. Concern will relate to the presence of the pollutant in some medium. The term might be as general as air or water, but will typically be more specific. At one extreme, a standard might be set to place a limit on the level of effect on a subject group, without actual reference to any pollutant which causes or influences that effect. The consequences, in terms of the effect on the subject group, of any particular level of pollutant in the medium are inherently uncertain. Standards will generally apply limits on some quantity such as a pollutant level. Concentrations of the pollutant will vary in time and throughout the medium at any location. This leads inevitably to sample variation.
