Health Impact Assessment


What is a health impact assessment?

A health impact assessment (HIA) is the estimation of the overall effects of a specified action on the health of a defined population. It is an approach that ensures that decision making at all levels consider the potential impacts of policies, programmes or a project on health and health inequalities. HIA identifies actions that can enhance positive effects and reduce or eliminate negative effects. It is a systematic process that can also be used to assess service models or programme delivery by helping to evaluate the environmental, health and well-being impacts of these developments. It is a combination of procedures, methods and tools by which a policy, programme or project may be assessed for its potential and effects on the health of a population, including the distribution of these effects within the population. 

Health impact assessments have been used on a wide range of policies from rural development to mental health. Examples of HIA include looking at the impact of a new motorway in a city, expansion of an airport, effects of waste management, economic development, the impacts of noise and air quality from traffic, new housing developments  and commercial ventures. Health impact assessments are gaining popularity both within the UK and internationally, particularly in relation to urban health impact assessments.  Two tools have been developed for this - Urban HIA Screening Tool (UrHIST) and Urban HIA methodology (UrHIA), see  


  1. To assess the potential health impacts, both positive and negative of projects.
  2. To improve the quality of public policy decisions by making recommendations that are likely to enhance predicted positive health impacts and minimize negative ones.

What does a health impact assessment do?

  1. It focuses on social and environmental justice
  2. It involves a multi-disciplinary, participatory approach
  3. It involves positive encouragement of public participation in the debate about public health issues
  4. It can bring public health issues into the foreground when organisations and parties are making decisions and policies

Four Core Values of a Health Impact Assessment

HIA is based on four values:

  1. Democracy
  2. Equity
  3. Sustainable development (i.e. development that meets the needs of the present without damaging the health or environment of future generations)
  4. Ethical use of evidence

Stages of a Health Impact Assessment

  1. Screening
  2. Scoping - with multidisciplinary steering group and negotiating favoured options
  3. Appraisal
  4. Recommendations
  5. Implementation
  6. Monitoring and evaluation


  • Select and analyse policies, programmes or projects for assessment.
  • Profile the selected population - who is likely to be affected and their characteristics
  • Use the screening process to see whether or not a full-scale HIA is needed.


  • Identify the potential health impacts by getting the information from the range of people who have an interest in the policy


  • Evaluate the importance, scale and likelihood of the potential impacts (analysis is similar to decision analysis)
  • Utilise health indicators  to detect variations in impact on different populations or groups.  In other words, being able to assess health inequalities. 
  • Utilise mixed methods (quantitative and qualitative) in data collection.  Consider any available health profiles and impact analysis.
  • Synthesize the evidence available in the published and unpublished literature with evidence from stakeholders and experts. 
  • Use a hierarchy of evidence to be able to classify the strength of your recommendations (similar to conducting a systematic review).


  • Report on the impacts and make recommendations for managing the impacts


  • Monitor actual impacts of your recommendations and take action where necessary.
  • This is likely to include process, impact and outcome evaluations.

Population Impact Analysis

Population impact analysis is a framework for applying the findings of systematic reviews of public health literature to estimating the impact upon a local population.  The aim is to help decision making by showing how scare resources can best be invested and the likely population impact of an intervention on a specific context.  This includes estimating the lives saved, admissions prevented and risk factors reduced by implementing an intervention and comparisons with other interventions. 

It's a four step process:

  1. Ask - identify the need and formulate a well-specified question
  2. Collect & Calculate - estimate the benefit and harm to the population of the intervention/policy.  (Population X baseline risk of hospitalisation/death/other outcome X population attributable risk)
  3. Understand - present the data in a clear understandable and relevant way.
  4. Use - feed into decision making process and implement change.

Population impact analysis can help with the synthesis of information to estimate the potential anticipated and unanticipated outcomes of proposed interventions or policies. 

Further Reading 

 WHO Health Impact Assessment page

Verma A et al.  Population Impact Analysis: a framework for assessing the population impact of a risk or intervention.  Journal of Public Health (2011):34(1):83-89.