'Specialists working on human-induced hazards, like chemical or nuclear plants, share a common goal with those working on natural hazards such as floods and earthquakes: to reduce the impact of hazards on people, property and the environment' (Kay and Alder, 1999 p. 193).

Engineering risk assessment has a long history and has traditionally attempted to make systems and structures more reliable. Gerrard (2000) explained the translation of these assessments from internal exercises to more explicit demonstrations intended to convince external audiences. Health risk assessment has subsequently developed and attempted to quantify the risks to people from exposure to different substances or activities. Environmental risk assessment is a more recent application, which also has some added difficulties.

Firstly, 'most [environmental management] decisions have to be taken on the basis of incomplete information and sometimes in circumstances of uncertainty. When potential damage is uncertain and may be significant it is necessary to act on the precautionary principle' (DoE, 1995 p.10).

At the same time the application of sustainable development theory requires us to balance 'positive environmental utilisation and potential environmental degradation, bearing in mind the needs of future generations' (DoE, 1995 p.12). Thus an environmental risk assessment involves judging the effects of an action or event on many varied components. Furthermore it must measure and judge the damaging nature of any effect and its environmental significance.

The DoE (1995 p. 14) concluded that for environmental risk assessment:

• Our duty of stewardship and commitment to sustainable development requires proper assessment of environmental risks;
• Analysis may facilitate a judgement and allow a more quantified judgement to be made;
• Inability to make a quantified judgement should not be used to avoid doing a risk assessment and it may indicate where more information should be sought;
• The identification of uncertainty and serious potential damage may indicate the need to invoke the precautionary principle or to so modify the intention as to render the risks tolerable;
• Analysis may indicate where regulatory measures are needed;
• A prognosis of an outcome provides the basis for monitoring and control; and
• Recorded analysis facilitates a reappraisal in changed circumstances or the light of new knowledge.