Making Predictions in HIA

HIA claims to be able to predict the health consequences of implementing different proposals. This is a bold claim.

For each proposal there will be numerous paths by which health could be affected some good impacts some bad.

Predictions are made by systematically exploring the different causal pathways by which a proposal could affect health. For example

• Build factory – Emit particulates – Damage to health
• Create cycle path – More physical activity – Better health
• Build by-pass – Reduced traffic in town – Better health

For each impact the HIA should seek to describe

• Its nature (death, illness, contentment)
• The direction of change (increased or decreased)
• Its size (how many people affected how severely).

Impacts may be predicted by epidemiological methods (exposure and dose response) or by participative methods (asking people about their hopes and fears if the proposal is implemented).

While HIA aspires to be able to say how big an impact will be in practice very few HIAs have adequately described the size of impacts (quantification).