The Design stage in an integrated environmental health impact assessment takes forward the 'conceptual model' of the issue, defined during issue framing, and converts it into a detailed protocol for assessment.

This is necessary because issue framing only defines what we would like to assess. It does not guarantee that an integrated assessment is worthwhile or can be done, nor does it set out how actually to do the assessment.

Designing the assessment requires three further preparatory steps:

• Screening – to determine whether a full integrated impact assessment is necessary;
• Piloting – to determine whether a full integrated impact assessment can be conducted successfully;
• Protocol development – to specify in detail the study area and population, scenario, data and methods that will be used in the assessment.

None of these steps runs only one way.  In many instances, they will reveal previously unforeseen factors that need to be included.  They may also uncover contradicting evidence which cast doubt on some of the decisions or expectations in issue framing.  As a consequence, the conceptual model of the issue may need to be reconsidered and revised. 

Nor is the complete process necessarily carried out, for the first step in this stage of the assessment (screening) may show that an assessment is not merited, while feasibility testing may show that it cannot be done.  In either of these situations, the assessment process can be terminated.  In this case, further consultation with stakeholders will be required to explain this outcome, and to consider what should be done instead.