Technical Reports

TR 088 : Environmental Risk Assessment of Difficult Substances | June 2003

Experience gained from the EU environmental risk assessments has shown that certain substances have properties that complicate the assessment of exposure and effects. Such substances, often referred to as 'difficult substances', are the subject of this report.
Also included are naturally occurring essential and multi-ionic elements, as these represent chemicals for which further scientific debate between the scientific community and the Regulatory Authorities is required, in order that realistic risk assessments can be performed.

The properties or attributes of the so-called 'difficult substances' have been analysed in relation to the problems arising from the assessment of the effects and/or exposure. Pragmatic guidance is presented to address these issues, so that more realistic assessments can be conducted. This report was produced with the intention that it should be a contribution to the revision of the EC Technical Guidance Document.

Properties and/or attributes that were specifically considered for this report are:

• Unstable and highly reactive;
• poorly water soluble;
• sorptive;
• surface active;
• volatile;
• naturally occurring, essential and multi-ionic elements.

It is clear that some substances may display more than one of these characteristics and thus, no single property should be considered in isolation. Therefore, a holistic approach should be applied when conducting a risk assessment for a 'difficult substance', taking into account the influence of all properties or attributes that can complicate the exercise.

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