Structures health impact assessment with exposure evaluation and risk characterization. Use when assessing health impacts, evaluating environmental exposures, or characterizing population risk.
Health Impact Assessments (HIAs) evaluate the potential health effects of proposed policies, programs, plans, or projects before they are implemented. Unlike environmental impact assessments (EIAs), HIAs specifically center population health and health equity, examining how decisions in non-health sectors — transportation, housing, land use, energy, agriculture — affect health determinants. The practice draws on the Gothenburg Consensus Paper (WHO 1999), the NRC risk assessment paradigm (hazard identification, dose-response, exposure assessment, risk characterization), and the Health Impact Project (Pew/RWJF) minimum elements. HIAs are required or recommended in several state and local jurisdictions and are a key tool for Health in All Policies (HiAP) initiatives. This skill structures the complete HIA process from screening through monitoring.
Determine whether an HIA is warranted and feasible:
Document the screening decision. If an HIA is not warranted, explain why. If warranted, specify the type (rapid, intermediate, or comprehensive) and proceed.
Define the boundaries and methods of the HIA:
Identify the health determinants and outcomes to be assessed. Use a causal pathway diagram: Proposal → Change in determinant → Change in exposure/behavior → Health outcome.
Prioritize pathways based on: magnitude of potential impact, severity of health outcome, size of affected population, and vulnerability of subpopulations.
Select assessment methods for each pathway: literature review, quantitative modeling (exposure modeling, burden-of-disease calculation, health economic analysis), qualitative analysis (community input, expert judgment), or spatial analysis (GIS).
Define the geographic and temporal scope of the assessment.
Develop a stakeholder engagement plan: identify who will be consulted, how community input will be collected (focus groups, public comment, participatory mapping), and how input will influence the assessment.
Establish the assessment team and their roles.
Health equity scoping --- Explicitly identify vulnerable subpopulations in the scoping phase: low-income communities, communities of color, children, elderly, persons with disabilities, unhoused persons, and recently arrived immigrants. For each subpopulation, assess baseline health status, cumulative environmental burden (using CalEnviroScreen or EPA EJScreen), and differential exposure to the proposed decision's effects.
For each prioritized pathway, characterize the baseline and predicted impact:
| Health Pathway | Quantitative Tool | Key Metrics |
|---|---|---|
| Air quality → respiratory/cardiovascular | EPA BenMAP-CE | Avoided premature deaths, avoided hospital admissions |
| Noise → annoyance/cardiovascular | WHO noise guidelines | DALYs, percent highly annoyed |
| Transportation → injury | Pedestrian/cyclist crash models | Predicted injuries/fatalities |
| Green space → mental health/physical activity | NDVI + dose-response | Estimated MET-hours gained, depression risk reduction |
| Housing → multiple outcomes | Housing quality indices | Lead exposure risk, mold-related asthma, displacement count |
| Economic → health via income | Income-health gradient models | Life expectancy change per income change |
Develop evidence-based recommendations to mitigate negative health impacts and enhance positive ones:
Write the HIA report following the standard structure: executive summary, background, methods, assessment findings by pathway, recommendations, and monitoring plan.
Present findings to the decision-maker within the decision timeline. An HIA that arrives after the decision is made has no influence.
Develop a monitoring plan that specifies: which health indicators will be tracked post-decision, data sources, monitoring frequency, responsible parties, and triggers for reassessment.
Track whether recommendations were adopted and whether predicted health impacts materialized. This evaluation feeds back into HIA practice improvement.
Publish the completed HIA in the Health Impact Project database and relevant peer-reviewed literature.
Evaluation of HIA effectiveness --- After the decision is made, evaluate the HIA's influence: were recommendations adopted? Did the HIA change the decision? Were predicted health impacts observed? Document lessons learned for future HIA practice in the jurisdiction.
Screening decision documented with rationale
Scoping identified priority pathways with causal diagrams
Baseline health profile completed for the affected community
Impact estimates provided for each priority pathway with direction and magnitude
Equity analysis conducted for all assessed impacts
Uncertainty characterized for each impact estimate
Recommendations are specific, actionable, and linked to findings
Report delivered within the decision timeline
Monitoring plan established with indicators, data sources, and responsible parties
Health equity analysis completed for all vulnerable subpopulations
Cumulative environmental burden assessed using CalEnviroScreen, EJScreen, or equivalent
Post-decision evaluation plan includes HIA influence assessment
Causal pathway diagrams are evidence-based and plausible (not speculative)
Exposure-response functions sourced from peer-reviewed literature or established models (EPA, WHO)
Quantitative estimates include sensitivity analysis for key assumptions
Community engagement was substantive — input influenced scoping and recommendations, not just cosmetic inclusion
SVI or equivalent equity index applied to identify disproportionately affected populations
Recommendations distinguish between design-phase mitigations and post-implementation monitoring
HIA followed Minimum Elements and Practice Standards for HIA (National Academies, 2011)
Report reviewed by multidisciplinary team (epidemiologist, environmental health specialist, community representative) before release
Health equity analysis identifies cumulative burden on vulnerable populations using validated indices
Quantitative methods reference peer-reviewed dose-response relationships
Post-decision evaluation plan assesses both recommendation adoption and health outcome monitoring
HIA report filed in the Health Impact Project database for practice advancement
An HIA is advisory, not regulatory. Its power comes from evidence quality and stakeholder legitimacy, not legal authority. Frame findings accordingly.
Timing is everything. An HIA must be completed before the decision is finalized. If the decision timeline is compressed, default to a rapid HIA rather than no HIA.
Do not overstate quantitative precision. If the best available evidence supports only a qualitative judgment (e.g., "likely to increase respiratory symptoms"), do not fabricate a numerical estimate.
Health equity must be central, not an appendix. Every impact pathway should be assessed for differential effects on vulnerable populations.
Distinguish between impacts the proposal causes directly (e.g., emissions from a new facility) and impacts that are correlated but not caused by the proposal (e.g., gentrification in a neighborhood where a transit project is proposed).
Community engagement must begin in scoping, not after the assessment is complete. Communities should help define which health issues matter, not just react to expert analysis.
Escalate to senior public health leadership or legal counsel when: the proposal involves a known carcinogen or hazardous exposure, the decision-maker is unresponsive to health findings, or political pressure is being applied to alter assessment conclusions.
Cumulative impact assessment is essential for environmental justice communities. A single project's air quality impact may be small, but it may be the 10th source of pollution in a community already overburdened. Use cumulative impact tools (CalEnviroScreen, EJScreen) to contextualize individual project impacts.
Economic impacts are health impacts. Changes in employment, income, housing affordability, and displacement have well-documented effects on health outcomes. Include economic determinants in every HIA scope, not just environmental exposures.3a:["$","$L42",null,{"content":"$43","frontMatter":{"name":"conducting-health-impact-assessments","description":"Structures health impact assessment with exposure evaluation and risk characterization. Use when assessing health impacts, evaluating environmental exposures, or characterizing population risk.","tags":["process","public-health","risk","valuation"],"metadata":{"author":"casemark","practice_areas":["Public Health","Epidemiology","Preventive Medicine"],"document_types":["Process Documentation"],"skill_modes":["Process Management"]}}}]