Assessment Criteria
Risk assessment is concerned with deciding whether estimated or
observed concentrations of contaminants actually matter, usually
through comparison with assessment criteria (guideline values).
When considering risks posed by land with contaminants and applying
assessment criteria, it is essential that they are appropriate to
the site under consideration. As paragraph B.48 in the Statutory
Guidance indicates:
- any assumptions underlying the value must be fully understood
and should not limit application to the site under
consideration
- the value must be appropriate to the site and receptor under
consideration
A common practice previously was to use guideline
values derived for generic situations either within or outside the
UK, such as ICRCL (now withdrawn by the Scottish and UK
Governments) or Dutch values. Such criteria should
not be used if the assumptions used in their
derivation are unknown or inappropriate, if the criteria are not
applicable to the site being assessed or if they have been derived
for receptors other than those under consideration. A number of
methods and models are available to assist in the derivation of
site specific assessment criteria, as highlighted in the other
"technical concepts and tools"
sections.