Screening in assessment design
- The text on this page is taken from an equivalent page of the IEHIAS-project.
The purpose of screening is to determine whether the issue being investigated merits a full integrated assessment. This is essential because assessment is a costly and time-consuming process, and can therefore be justified only if:
- the issue itself is relatively complex, so other, more restricted assessments are not appropriate;
- the likely impacts in terms of public health and associated consequences are relatively large;
- the levels of uncertainty involved are sufficiently small to make the results of the assessment meaningful and useful in decision making.
Screening thus consists of doing a ‘rough and ready’ assessment in order to evaluate the general order of magnitude of potential impacts, relative to the likely uncertainties. This can be done in three main ways:
- expert estimation – e.g. by surveying the opinions of experts or other stakeholders;
- extrapolation - from previous studies or survey/monitoring data;
- Rapid modellingrapid modelling – using simple modelling tools.
Which is used is likely to depend on the issue and status of the science, as well as the resources available for the assessment. Because of the inevitable uncertainties involved in all three of these approaches, however, there are advantages in not relying on any one of them, but instead ‘triangulating’ – i.e. using all three methods to compare (and if appropriate deriving some weighted average of) their results. This is not only likely to improve the reliability of the estimates, but also gives stakeholders more trust in the results. The latter point is especially important where screening leads to the decision not to continue with a full assessment – a conclusion that may need to be carefully explained and justified to the stakeholders concerned.