Health impact assessment (HIA) tools and methods

Health Impact Assessment (HIA) is a practical approach used to judge the potential health effects of a policy, programme or project on a population, particularly on vulnerable or disadvantaged groups. Recommendations are produced for decision-makers and stakeholders, with the aim of maximizing the proposal's positive health effects and minimizing its negative health effects. The approach can be applied in diverse economic sectors and uses quantitative, qualitative and participatory techniques. 

HIA provides a way to engage with members of the public affected by a particular proposal. It also helps decision-makers make choices about alternatives and improvements to prevent disease or injury and to actively promote health. It is based on the four interlinked values of democracy (promoting stakeholder participation), equity (considering the impact on the whole population), sustainable development and the ethical use of evidence. 

WHO supports tools and initiatives in health impact assessment to dynamically improve health and well-being across sectors. 

How to undertake an HIA

Health Impact Assessment (HIA) provides decision-makers and stake-holders with comprehensive information about the consequences on the health of interventions, policies, and projects. HIA has been used for example:

- Clean energy options, master plans, planning for green spaces, transportation and urban growth projects, zoning for walkability.

- Guidance documents often break HIA into four, five or six stages. Despite the differing number of stages, it is important to note that there are no significant differences between the methods that usually include screening, scoping, appraisal, reporting, and monitoring activities. 

Health Impact Assessment summary
  • Screening  

The screening stage selects an intervention, a policy or a project for which an HIA would be beneficial. Potential effects on the determinants of health, health outcome and population groups are identified. Screening results in three types of decisions 1) HIA is needed; 2) HIA is not needed, as the effects are already known; 3) HIA is not needed, as the effects are negligible. 

  • Scoping  

The second step is the planning of the HIA and identifying what health risks and benefits to consider. A steering group is created and to develop and adopt the terms of reference for the HIA. Scoping involves bringing together the major stakeholders of the proposal by creating a steering group and developing and adopting terms of reference for the HIA. In the development of the HIA to reduce the risk of presenting only one side of the evidence, it is important to be systematic. 

  • Appraisal  

An appraisal is the core of any HIA activity. All the data and evidence are gathered and analyzed, affected populations are identified, and health impacts are estimated. The impact estimates allow giving suggestions and recommendations for actions that promote positive health effects and minimize negative health effects. Depending on the context, an HIA can be conducted with a rapid appraisal or with a comprehensive appraisal. 

  • Reporting  

Presenting clear results to communities and decision-makers is an important step in HIA. The contents of the report should include a description of the scope, the priorities identified at the beginning of the process, the views expressed by the stakeholders, the evidence available from the various sources, the overall findings, and any recommendations. 

  • Monitoring  

It is the final step in the HIA process and allows to evaluate the process and the effectiveness of the HIA. 

Evaluating whether the HIA has influenced the decision-making process (and the subsequent proposal) is an important component of HIA. As with any intervention, evaluation is required to see if it has worked. 

Monitoring the implementation of the proposal is critical to ensure that any recommendations that decision-makers agreed to, actually occur. Longer-term monitoring of the health of populations is sometimes a component of larger proposals. This long-term monitoring can be used to see if the predictions made during the appraisal were accurate, and to see if the health, or health-promoting behaviours, of the community, have improved. 

Other resources

Other impacts assessment tools

Many different methods and tools can be used within HIA, risk assessment and cost-benefit analysis are among the most common:

  • Risk assessment 

Risk assessment is a systematic approach to quantify the burden of disease/injury resulting from risk factors. Risks are defined as the probability of an adverse event (eg admission to hospital for respiratory problems when pollution levels increase) and/or a factor that raises the probability of an adverse event (living close to a busy road). 

Risk assessment information can be used in the appraisal stage of HIA, to help understand the potential relationship between the proposal and the determinants of health. Risk assessment can be used for those risk factors where there is good quantitative evidence of a dose-response relationship and clear exposure. It can also be used for priority setting among the risks identified. 

  • Cost-benefit analysis 

Building on the risk assessment work that quantifies the burden of disease, cost-benefit analysis of interventions is undertaken to help identify interventions that will reduce the burden of disease. There are many ways to undertake such analyses and standard methods are available. Often within public health, it is difficult to get the necessary information to carry out cost-benefit analyses of population-based interventions: far more information exists for individual-based interventions. 

Cost-benefit information can be used in the appraisal and recommendations stages of HIA, to help understand the potential relationship between the proposal and the determinants of health, and to help identify recommendations for altering the proposal to improve health. 

  • Examples of HIA 

HIA is a consolidated approach to estimate and anticipate the consequences of policies, plans, programmes and projects. It is a key resource for achieving foresight in societal decision-making, systematically deployed worldwide. Several HIA websites provide reviews about the effectiveness of interventions. Searching this website and the HIA Gateway are good starting points. Many other organizations and collaborations have specific responsibility for undertaking reviews and are listed in the Health Development Advice (HDA) evidence base.