Health impact assessment

Health Impact Assessment (HIA) provides a framework and procedure for estimating the impact of a proposed programme or policy action on a selected environmental health issue for a defined population.


HIA seeks to improve the quality of policy decisions by evaluating the likely positive and negative health impacts from proposed programmes or policies, and making recommendatio ns to improve positive health impacts and mitigate negative ones. HIA stresses the participation of public stakeholders and provides for a social model of health and well-being in which there is an explicit focus on equity, sustainability and social justice, and a commitment to openness and public scrutiny. It can be included as part of an Environmental Impact Assessment (EIA), Strategic Environmental Assessment (SEA), Social Impact Assessment (SIA), or Integrated Impact Assessment (IIA).


HIA is typically a prospective assessment of a programme or intervention beforeimplementation, although it may be carried out concurrently or retrospectively. HIA gathers opinions and concerns regarding the proposed policy: and uses knowledge of health determin ants as to the expected impacts of the proposed policy or intervention, and describes the expected health impacts using both quantitative and qualitative methods as appropriate. There is no one definitive methodology for EHIA/HIA, although several toolkits are being (and have been) developed.

Procedures in health impact assessment


  • Screening determines the potential health implications of the policy or project under consideration to determine if an HIA is, in fact, required.


  • Key health issues and public concerns are identified that should be considered in the assessment. Health determinants that may be included in the scope of the review include factors such as the social and physical environment (i.e. housing quality, crime rates, and social networks), personal or family circumstances (i.e. diet, exercise, risk-taking behaviour, and employment), and access to public services.


  • Within the defined scope, available evidence is gathered and used to estimate the potential health gains or losses.
  • Considerations should include questions as to who will be affected by the proposed policy intervention or set of interventions and a review of baseline data indicating current population health status in the areas defined as determinants
  • Predictions are made as to likely changes in health status as a result of the intervention, and possible strategies that would mitigate environment and health impacts.
  • Rapid or in-depth assessment procedures may be chosen depending on limitations of time, budget and epidemiological/quantitative evidence.


  • Conclusions are drawn from available data, and recommendations are made that might remove/mitigate negative impacts on environment and health, and enhance positive benefits.


  • Action, where appropriate, is taken in order to monitor the actual impacts on health of the intervention, and to enhance the existing evidence base regarding impacts

Relevance to policy making

Decision-makers, in general, lack effective tools for assessing the health costs and benefits of various policy options that they may wish to consider. At the same time, health authorities do not have direct control over policy determinants in areas such as industry, transport and agriculture that may impact environmental health.

EIA methods have gained broad acceptance as a method for protecting the environment from potentially negative impacts of development. But while formally, health has long been a part of EIA procedures, in practice, it has been conspicuous ly absent from the process. This is despite the fact that many projects scrutinized by EIAs carry associated environment and health risks.

Whether integrated into a broader Impact Assessment, or as a stand-alone tool, HIA can play a vital role in awareness-raising, promoting public participation, and placing health on the agenda of all development sectors. More concretely, it can be used as a procedure for deciding between policy alternatives. Requirements for HIA are now emerging in the form of a UNECE Strategic Environmental Assessment (SEA) Protocol, mandating assessment of health impacts at all stages of the SEA process. The European Community’s public health strategy also focuses on HIA. European Community directorates also require health assessments within EIA and SEA directives.

Example 1: HIA in a municipal policy debate

HIA can highlight instances where environmental policies bring about health improvements, or help focus on the environmental policy option which will facilitate maximum health gain. Recently, proposals for the City of Edinburgh's transport strategy underwent a HIA by the local public health organization and the municipal council. It suggested that one option being considered would bring about health gain by reducing road traffic accidents, increasing physical activity (and thus reducing health, promoting community networks, and reducing air pollution. This option aimed to facilitate walking and cycling, develop public transport, and integrate transport policy with land use policy. The HIA influenced city policy and decision-making. The result was a transport strategy that had more positive benefits for the environment, as well as to public health.

Example 2: A health and equity assessment of a large oil project in Africa

An example of appraisal can be drawn from a health and equity assessment of a large oil project in Africa. The World Bank required the Chad and Cameroon Governments to hire a panel of experts to guide the assessment process. The panel drew documents provided by the construction consortium that provided information on a limited number of determinants of health, social and economic issues, wildlife and biodiversity. The papers also listed specific health hazards and diseases prevalent in the project area. The relationship between the determinants of health and key elements of the proposal was investigated. In this study, normal procedures for collecting field data via interviews, focus groups, surveys, etc. did not occur. The experts believed this provided a barrier to carrying out a thorough appraisal, and instead carried out a secondary analysis of existing data to estimate likely number of deaths per year from the most important he alth and safety risks. By far, the largest risk posed was the transmission of HIV via truck drivers transporting pipeline products from a port in Cameroon, where HIV infection rates are high, over 1000 kilometres into the interior of southern Chad, where infection rates are far lower. The role of long-distance truck drivers is important in the spread of HIV in Africa.


UK HIA Gateway,
Jobin W., Health and Equity Assessment of a Large Oil Project in Africa , Bulletin of the WHO - International Journal of Public Health, Forthcoming.
WHO, Health Impact Assessment in Development Policy and Planning, Report of an Informal WHO Consultative Meeting, Cartagena, Columbia, May 28, 2001, (available on PDF at:
Dora C, A Different Route to Health: Implications of Transport Policies , BMJ, 318:1686-1689: 1999.
Barnes R. & Scott -Samuel A., Health Impact Assessment: A Ten Minute Guide , (
Scott-Samuel A, Birley M. and Ardern K., The Merseyside Guidelines for Health Impact Assessment , Liverpool: Merseyside Health Impact Assessment Steering Group, Liverpool, November 1998, (
Office of Environmental Health Assessment , Environmental Assessment and Human Health: Perspectives, Approaches and Future Directions, Health Canada, May 1997, (
British Department of Health, Health Impact Assessment: Report of a Methodological Seminar , ( )
Welsh Assembly: Developing Health Impact Assessment in Wales (