Methodology: Models (Taxonomy of HIA) - Health Impact Assessment

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Overview of HIA - PDF (315 KB)

Methodology: Models (taxonomy of HIA)

Differing disciplinary traditions and applications have given rise to several distinct approaches to HIA around the world. Generally these can be classified into one of three categories-1) community dialogue, 2) quantitative analysis and 3) bureaucratic pragmatism. Each of these has its own strengths and limitations that make them more or less suitable for the analysis of different policy initiatives in different policy-making contexts.

1. Community Dialogue
The focus of this approach is on public participation in decision-making, with community members actively engaged with planners in raising concerns and developing ideas for alternatives and/or for the mitigation of impacts. Assessments tend to be qualitative. When quantitative methods are used their role is to facilitate better public decision-making; not to indicate which decision is better. This approach's emphasis on community participation and consensus-based decision-making is similar to and may stem from that of the World Health Organization's "Healthy Cities Movement."

Strengths: This approach fits well with practices of democratic governance. A broad range of potential impacts and concerns is considered. Although involving the public may be perceived as time-consuming, this can actually be a fairly efficient process for generating ideas about significant concerns and possible alternatives.

Limitations: It is not very replicable or testable. Comparisons between projects and with standards are difficult since there are no common metrics. Decisions based on this approach may be difficult to support in a litigious legal system that puts a premium on quantitative "scientific" data. Issues may also arise about who represents the "community." While this approach does a good job of highlighting potential impacts, it is often lacking in the evaluation and documentation of those impacts. Likewise, levels of uncertainty are not well addressed.

Examples:

Fleeman N, Scott-Samuel A. A prospective health impact assessment of the Merseyside Integrated Transport Strategy (MerITS). Journal of Public Health Medicine, 2000, 22(3):268-274.
Winters LY. A prospective health impact assessment of the international astronomy and space exploration center. Journal of Epidemiology and Community Health, 2001 55:433-441.
Landstingsforbundet. Examples of how to start up and implement Health Impact Assessments (HIA: Stockholm County Council, Southwestern Health District). Available on-line at: http:www.lf.se/hkb/engelskversion/practice.htm.

2. Quantitative Analysis - Risk Analysis and Others
Overview: This approach goes beyond the simple quantification of data to attempt to predict impacts based on a systematic analysis involving a careful specification of outcomes and program effects, applying methods from economics, toxicology, risk analysis and especially epidemiology. While traditional epidemiologic studies focus on estimating the causal relation between one or more exposures and the occurrence of a single disease or health outcome in a population, HIAs focus on the combined impact of one or more interventions (e.g. policies) on multiple health outcomes. These impacts can be measured in different ways, including: number of prevented deaths, years of life gained (or lost) (YLL), quality-adjusted years of life gained (e.g. QALYs and DALYs), cost-effectiveness ratio (e.g. dollars per QALY) and net monetary benefit (benefits - costs). By bringing together large amounts of information in a common metric, these measures facilitate the comparison of potential impacts of various policy alternatives.

Strengths: Assessments using a systematic quantitative approach as outlined above are testable and reproducible. They provide common measures that facilitate comparison of alternatives and on-going monitoring of program impacts. The apparent objectivity of this approach makes it legally defensible; however, its assumptions and uncertainty in projections also make it vulnerable to legal challenge by competing experts. Methodologies based on a potential-outcomes model can be applied to cumulative or time-dependent exposures, such as in computer simulation modeling.

Limitations: These assessments are usually highly time- and cost-intensive which restricts their widespread application. Limits on time, money and data usually restrict their focus to single, unmixed, non-cumulative exposures and only one or a few outcomes, limiting their usefulness as a tool for evaluating policies with multiple outcomes. While this type of quantitative assessment may tend to be more objective than other approaches, it involves numerous value- and model-based assumptions that may or may not be made explicit. Assumptions are especially problematic for HIAs utilizing the "burden of disease" approach, since these methods examine the impacts of outcomes extant in the population, not the impact of interventions themselves.

Examples

Ale BJ, Piers M. The assessment and management of third party risk around a major airport. Journal of Hazardous Materials, 2000, 71(1-3):1-16.
De Hollander EM, Melse JM, Lebret, E, Kramers PGN. An aggregate public health indicator to represent the impact of multiple environmental exposures. Epidemiology, 1999, 10(5):606-617.
Fehr R. Environmental health impact assessment: evaluation of a ten-step model. Epidemiology, 1999, 10(5):618-25.
Hammitt JK et al. Residential building codes, affordability and health protection: a risk-tradeoff approach. Risk Analysis, 1999, 19(6):1037-58.
Ponce RA et al. Use of quality-adjusted life year weights with does-response models for public health decisions: a case study of the risks and benefits of fish consumption. Risk Analysis, 2000, 20(4):529-42.

3. Bureaucratic Pragmatism

This approach represents a hybrid of the other two approaches, usually focusing on a specific project, program or policy being considered for approval by a government agency. It is driven by procedural requirements to efficiently assess impacts, as specified in a regulation or agency rule. In contrast, to the "Quantitative Analysis Approach," which places a premium on accuracy and methodological sophistication, "Bureaucratic Pragmatism" emphasizes the selection of methods based on regulations and expediency. A single assessment may consider a range of impacts, using many different methods from checklists discussed in community meetings to highly sophisticated computer modeling techniques.

Strengths: This approach can be relatively quick and efficient, compared to the "Quantitative Analysis Approach," although agency rules and regulations specifying content and methods can greatly increase resource requirements for this type of assessment, as has been the case with environmental impact statements in the U.S. Methods are usually standardized. There is also usually some requirement for stakeholder involvement, such as in the scoping and screening of environmental impact assessments under NEPA.

Limitations: Assessments within this approach, while taking elements of the first two approaches, may not do either well. Bureaucratic imperatives to make a decision with limited resources in a limited amount of time, may compromise the analytic rigor of approach #2, "quantitative analysis," and the degree of meaningful public participation emphasized in approach #1. Some analyses may be ad hoc and subjective, with the use of numbers to give a patina of objectivity and expert sophistication. Public participation may be limited to nothing more than a vetting of decisions already made. There is also some question as to whether assessments are really used in the decision-making process, or whether they are just conducted to fulfill a bureaucratic requirement.

Examples

Health Canada. The Canadian Handbook on Health Impact Assessment, 2000. Available on-line at: http://www.hc-sc.gc.ca/ehd/oeha/hia. (In general, the HIA approaches described in this overview of methods and policies seem to fit best under this category, but since individual projects are not discussed in detail, this categorization is tentative.)
Rosenberg BJ et al. The work environment impact assessment: a methodologic framework for evaluating health-based interventions. American Journal of Industrial Medicine, 2001, 39:218-226.