Scottish HIA network - how to HIA guides

This section summarises the basic principles of HIA. Our guides to Health Impact Screening and Detailed HIA are also available to download from this page.


What HIA is

In 1999, the WHO Gothenburg Consensus Paper (external link) defined health impact assessment (HIA) as:

“A combination of procedures, methods and tools by which a policy, program or project may be judged as to its potential effects on the health of a population, and the distribution of those effects within the population.”

The purpose of HIA is to:
  • predict likely health impacts of a specific proposal in a specific context, and identify who will bear these impacts
  • involve stakeholders so their views and values may be taken into account
  • inform decision making so that positive health impacts may be maximised and negative health impacts minimised.

View values of HIA

HIA involves an attempt to identify and assess all the likely health impacts of a proposal, especially those that are unintended and not previously considered by the developers of the proposal.

HIA uses a range of sources of qualitative and quantitative evidence that includes public health, epidemiological, toxicological and medical knowledge as well as public and other stakeholders´ views and experiences. It is important to apply the evidence gathered during the assessment to the specific context in order to predict the likely impacts in the defined place and populations.

As HIA aims to inform the policy and decision-making process it is best carried out prospectively at a stage when a proposal is clear enough to be assessed and there is still an opportunity to make changes to the proposal. In some instances, HIA may be done concurrently or retrospectively. It is important in these cases to ensure that there is still an opportunity to influence the proposal.

The HIA needs to fit within the appropriate decision making framework. This often causes a tension over the timing of the assessment. It needs to be done early enough to inform the relevant decisions, but cannot be too early, before the proposal is sufficiently well developed to make an assessment of its impacts. Those doing an HIA need an understanding of these decision-making processes and structures to ensure the HIA is able to influence and inform change.

There are other benefits that may be gained from doing health impact assessment. It may increase awareness of health among decision makers in other sectors and facilitate inter-sectoral working more widely. The emphasis on stakeholders’ views is also likely to facilitate community involvement in decision making. However this should not detract from the main purpose as stated above.

What HIA is not

HIA should be differentiated from other activities including primary research and evaluation although these may provide evidence to be used within HIA.

It is also important to differentiate between HIA and consultation. An HIA offers more than simply a consultation exercise with stakeholders. It will present the findings in terms of the health impacts, include other forms of evidence and involve further assessment of the impacts. An HIA does not absolve decision makers of their responsibility to consult on their decisions.

HIA may be used by communities and being involved in HIA may give a voice to groups that are not otherwise heard. But HIA should be differentiated from community development. The primary aim of HIA is to assess one specific proposal whereas community development activities will involve a much wider range of activities whose primary aim is to build community capacity.

Health impact assessment should not be used as a form of advocacy, either for or against the proposal. The HIA should be done impartially and the recommendations should be based on the evidence of health impacts rather than on a pre-existing stance. However, following the HIA it may be appropriate for the HIA practitioners to advocate for adoption of the recommendations.

Finally, HIA is a decision making support process but not a decision making process. While HIA may clarify the nature of trade offs to be made and the consequences of choosing the different options, it does not make the value judgements needed to choose between those options. This responsibility remains with the decision maker.




Values of HIA

The Gothenburg Consensus Paper identified four values to underpin HIA. The values, and their implications, are:
  1. democracy - HIA should involve and engage different stakeholders, and the process and results should be as transparent and accessible as possible. Stakeholders include all the people who will be affected by or have an interest in the policy or decision.
  2. equity - consideration of health inequalities should be central to all health impact assessments. HIA should assess not only aggregate impacts but also the distribution of health impacts across the population, in terms of gender, age, ethnic background, faith, sexual orientation, socio-economic status and other characteristics. A health impact assessment should identify different groups that may bear different impacts, and show how each group will be affected, positively or negatively. Those doing HIA should make special attempts to help the most vulnerable people to participate. In order to reduce inequalities in health, recommendations should aim to maximise the benefits to the most vulnerable groups.
  3. sustainable development - HIA should predict short and long-term impacts of a proposal, and consider reversibility of impacts and what weight should be given to impacts expected in the far distant future (to what extent they should be discounted).
  4. ethical use of evidence - this means that HIA should use appropriate evidence to predict impacts and inform recommendations. HIA should not set out to support or refute the proposal and should be rigorous and transparent.

Updated 10 April 2015

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