At a glance
CDC’s Tracking Network is an excellent data source for environmental hazards, exposures, and health conditions, making it a valuable asset to the health impact assessment (HIA) process. The Tracking Network provides national, state, and local data that may be used in several HIA steps, including community engagement, scoping, assessment, and evaluation.
About Health Impact Assessments (HIA)
An HIA is a process to evaluate the potential positive and negative public health effects of a plan, project, or policy before it is approved, built, or implemented.
Governments, community organizations, and other groups are increasingly conducting HIAs. These HIAs inform decision-making processes for transportation, land use, climate change, and other sectors.
Conducting an HIA requires access to high-quality data about many different areas that affect our health. These include environmental, cultural, economic, and social conditions.
Types of Data
Data on the National Tracking Network
CDC's Tracking Network includes data about community design elements, asthma, outdoor air quality, socioeconomic indicators, and more. Explore these data on the Tracking Network's Data Explorer. Visit the data user's guide (below) for information about how to use Tracking Network data in an HIA.
Data on State and Local Networks
CDC funds health departments to build and maintain local tracking networks as part of the national Tracking Network. These local networks may include data that are not on CDC's website. Some of these unique data also may be helpful for conducting HIAs. Access all state and local networks from this page.
Custom Data
In addition to providing data through the websites, state and local tracking programs can provide custom data by request. For example, some state or local tracking programs can provide data for specific ZIP codes or at a community level. State and local tracking programs can assist with interpretation and visualization of the data. For more information, contact the CDC Tracking Program or explore the state and local networks.
Tracking Network Diagrams and Case Studies by HIA
Case Study & Diagram: Transportation
Transportation planning and design provides a great opportunity to protect public health. Careful transportation planning can help reduce air pollution, especially fine particles and ozone. It can also promote physical activity. This can help reduce obesity and prevent physical injuries, and improve cardiovascular, respiratory, and mental health.
Major transportation corridors often create pollution levels that are higher than in ambient air. These corridors include populations that may have many health and environmental concerns. Examples include high rates of asthma, poor air quality, and poverty/low incomes. HIAs can help prevent or reduce additional burdens on these communities.
For transportation related HIAs, the Tracking Network has the following types of data.
- Food access
- Community design
- Asthma prevalence, hospital stays, and emergency department visits
- Heart attack hospital stays
- Outdoor air quality (ozone and fine particulate matter)
- Population demographics and socioeconomic measures
Case Study & Diagram: Land Use
Land use decisions affect people's health and how they live. Communities that are designed to encourage physical activity, such as walking and biking, help promote healthy behaviors. These healthy behaviors, in turn, can reduce obesity and chronic diseases like diabetes and heart disease. Land use refers to a broad set of community design and built environment topics. These include zoning, access to parks, walkability, and transportation.
For land use HIAs, the Tracking Network has the following types of data.
- Land cover and land use
- Outdoor air quality
- Community design
- Population demographics and socioeconomic measures
- Asthma prevalence, hospital stays, and emergency department visits
- Heart attack hospital stays
- Age of housing
Case Study & Diagram: Climate Change
Evidence suggests that the world's climate is becoming warmer. While climate predictions vary by region in the United States, more extreme weather is likely to occur. This will increase the potential for the kinds of environmental hazards listed below.
- More intense tropical cyclones
- More frequent and severe heat waves
- More frequent and intense tornadoes
- Increased precipitation or drought
- More frequent heavy precipitation events
- Flooding as a result of heavy precipitation
- Sea level increases
- Additional air pollution
- Increased risk and extent of wildfires
Many local communities are forming action plans to prepare for their adaptation to a changing climate. Assessing current and projected health effects may help communities estimate how their changing climate, without further adaptation, may affect their health and environment.
To assist with a climate related HIA, the Tracking Network has data on the following topics.
- Outdoor air quality
- Asthma
- Chronic obstructive pulmonary disease
- Drought
- Heart disease & stroke
- Heat & heat-related illness
- Populations & vulnerabilities
- Precipitation & flooding
- Tornados
View Climate Diagram (Heat and Ozone)
You can read more about CDC's climate adaptation work on the Climate and Health Program website.
HIA Data Guide
This guide provides suggestions for how to use data from the Tracking Network in an HIA. Users who are new to HIA practices are encouraged to seek background information about HIAs.
Tracking data may be used to inform any of the six steps for conducting an HIA. However, this guide focuses on three specific steps.
Scoping
To explore health and environment issues of potential interest to a community or when conducting an HIA
Assessment
To assess a baseline for conditions, refine priorities, inform communities, or make projections or estimates about trends
Monitoring and Evaluation
To evaluate the effects of a decision, policy, or action over time; pre- and post-implementation
Data Guide: Scoping
When conducting HIAs, scoping is a process that defines what the assessment will address. This includes geographic and time boundaries, health issues, people potentially affected, and data sources. Scoping helps create a viable work plan and timeline. This step is usually informed by the concerns identified during the stakeholder engagement process, from professional or expert opinions, and by relevant literature.
For more information about engaging stakeholders, see Guidance and Best Practices for Stakeholder Participation in Health Impact Assessments: Version 1.0. For more information about conducting HIAs, see CDC's Healthy Places Health Impact Assessment website.
The Tracking Network can be useful for two specific parts of the scoping step.
Pathway Diagrams
A central task of the scoping step is determining how the decision or project can impact health. You can facilitate this by developing pathway diagrams which illustrate the steps from decision to health outcome. Pathway diagrams help identify health effects and benefits. Tracking Network data can be used to assess these effects by providing baseline information about health status in a community or by predicting effects and benefits from a policy, plan, or project.
Identifying Questions and Data
Another key task of the scoping step is identifying the research questions, data sources, and analytic methods that will be used. The Tracking Network can be a source of data for this step. See an example of an HIA scoping worksheet from Human Impact Partners.
Data Guide: Assessment
In this step of an HIA, Tracking Network data may be used to evaluate the health effects and benefits of a plan, project, program, or policy. This can be accomplished by:
- Assessing baseline health conditions.
- Identifying and characterizing vulnerable populations, health disparities, and health inequities.
- Evaluating the direction and magnitude of potential health effects due to changes in exposure or actions to protect health.
For example, HIA practitioners and communities may want to know more about asthma in a particular area. CDC's Tracking Network can provide data about asthma hospitalizations and emergency department visits at state and county levels to establish a baseline health estimate and provide information on geographic areas within the region of interest. State and local tracking programs also may have asthma data at different levels of geography, such as ZIP code.
The assessment step in the HIA process also may include projections. These can be used to evaluate the direction and magnitude of potential health effects due to changes in exposure or actions to protect health. Tracking data may be used in quantitative or qualitative assessments to make informed projections based on trends over time.
Data Guide: Monitoring and Evaluation
Tracking Network data are updated on an ongoing basis. This makes Tracking Network data especially useful for monitoring and evaluating actions and decisions over time. For example, Tracking Network data can be used to evaluate progress pre- and post-implementation of the HIA decision or action. Furthermore, Tracking Network data are developed to be nationally consistent, which helps with comparisons from one area or population to another.
Data Guide: Consultation and Expertise
CDC Tracking Program staff and staff from state and local tracking programs have expertise in several areas.
- Data analysis and interpretation
- Data visualization (charts, maps/GIS)
- Communication message development and risk communication
HIA practitioners who have questions about tracking data, or need technical assistance, may contact CDC’s Tracking Program or the state and local tracking programs.
Data Guide: Analysis and Tools
Geographic Information Systems (GIS) are useful tools for analyzing and visualizing results for a proposed HIA. GIS maps can:
- show geographic boundaries of the area of interest.
- identify and determine accessibility to community attributes (e.g., green space, recreational areas, stores, public services).
- present health, demographic, and environmental data at different geographical scales (i.e., census tract, zip code, or community level).
- use spatial interpolation tools (e.g., ESRI's ArcGIS Spatial Analyst or Epi-Info).
CDC's Tracking Network and the state and local tracking networks offer dynamic mapping capabilities for most of the data available in the surveillance systems. You can view data with a number of different mapping options and request technical assistance with mapping if needed.
Attributable risk estimates may be used to quantify rates of death and illness associated with changes in exposure. These types of estimates can be made using the US EPA Environmental Benefits Mapping and Analysis Program (BenMAP). This is a free program that applies concentration-response functions from published studies to estimate changes in the burden of health effects associated with changes in air temperature or quality. BenMAP does not have the same spatial analysis capabilities as GIS. But it can be useful for contributing to attributable risk estimates.