Health Impact Assessment (HIA) provide decision-makers and stakeholders with comprehensive information about the consequences on health of interventions, policies, and projects. 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, decision-making and monitoring/follow-up activities.

Source: World Health Organization Regional Office for Europe (2023). A place in the public health toolbox: policy brief on health impact assessments and incorporating health into environmental assessments. Copenhagen, Denmark: WHO Regional Office for Europe

Health impact assessments begin by identifying the relevant stakeholders. This usually produces a large number of relevant people and organizations. HIA is a framework to implicate stakeholders in a meaningful way, allowing their messages to be heard. The process draws on all resources in the project and wider community to help guide decision making, including developers and planners, employers and unions, local and national health workers, and those living in the community—particularly the most vulnerable members of the community and those directly impacted by the programme or project. 

Because HIA provides a way to engage with members of the public affected by a particular proposal, it can show that an organization or partnership wants to involve a community and is willing to respond constructively to their concerns. The views of the public can be considered alongside expert opinion and scientific data, with each source of information being valued equally within the HIA. The resulting decisions are often more easily accepted by all stakeholders because they are based on the ideals of transparency and active participation.

Screening

The HIA process begins with screening activities meant to quickly establish the health relevance of the policy, programme or project. It then investigates the key issues and public concerns and creates boundaries and expectations. 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

Appraisal is the core of any HIA activity. All the data and evidence are gathered and analysed, affected populations are identified, and health impacts are estimated. In the appraisal phase, a rapid or in-depth assessment is completed on the health impacts of the project with a focus on those most affected. The impact estimates allow to give suggestions and recommendations for actions that promote positive health effects and minimize negative health effects. Depending from 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.

Decision making and recommendations

Developing and formulating conclusions and recommendations is the stage where conclusions and recommendations (and usually a set of recommended changes to the proposal) are presented on the positive and negative aspects to help guide decision making.

Monitoring

When the project is complete or the policy is initiated, HIA begins the monitoring phase, in which the impacts are recorded and analysed to enhance the existing evidence base and better inform later developments. 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.

Different methods can be used within HIA, risk assessment and cost-benefit analysis are among the most common. Additionally, there are other processes that are used to assess the impacts of policies, Strategic Environmental Assessment (SEA) and Environmental Impact Assessment (EIA) just to mention the main ones. 

Risk assessment

Risk assessment consists of “scientific analyses, the results of which are quantitative or qualitative expressions of the likelihood of harm” associated with an exposure, e.g., to a chemical substance.

It 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 (e.g. 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 burden of disease, cost benefit analysis of interventions is undertaken to help identify interventions that will reduce 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.

Environmental impact assessment (EIA) and strategic environmental assessment (SEA)

“Environmental assessment” is an umbrella term. It includes assessments both at a project level, called environmental impact assessments (EIAs), and at a strategic level, such as that of a policy, strategy, plan or programme, called strategic environmental assessments (SEAs).

While EIAs were established in 1960^th in the United States of America to assess the likely significant effects of infrastructure projects, SEAs were developed in the late 1980s to address the likely significant effects at higher decision-making tiers, and thus at an earlier stage in the process.

There is now a statutory requirement for EIA to be undertaken in almost all countries in the world. The process should lead to proposals which are likely to have significant adverse effects on the environment being, abandoned or modified. However, EIA does not typically include an assessment of the health effects of proposals, and when it does it is often narrowly focused on biophysical determinants and solely quantitative in nature.