Health Impact Assessment

Transportation planning and design provides a great opportunity to protect public health. Careful transportation planning can:

• promote physical activity which can help reduce obesity and prevent physical injuries, and improve cardiovascular, respiratory, and mental health
• reduce air pollution, especially fine particles and ozone.

Major transportation corridors often create pollution levels that are higher than in ambient air and they include vulnerable populations that may have many health and environmental concern (e.g., high rates of asthma, poor air quality, and poverty/low incomes). HIAs can help prevent or reduce additional burdens on these communities. For more information, and case studies, see the Transportation HIA Toolkit.

For Transportation related HIAs, the Tracking Network has

• community design data as motor vehicle fatalities, access to parks and schools, and types of transportation to work
• asthma hospital stays, prevalence, and emergency department visits
• heart attack hospital stays
• outdoor air quality measures for ozone and fine particulate matter (PM_2.5)
• a health impact assessment tool that estimates the number of deaths that could be prevented by lowering PM_2.5 concentration levels
• population demographics and socioeconomic measures

View Transportation Diagram

Land use decisions affect how people live and their health. Communities that are designed to encourage physical activity, such as walking and biking, help promote healthy behaviors. These healthy behaviors, in turn, reduce obesity and chronic diseases such diabetes and heart disease. Land use refers to a broad set of community design and built environment topics, including zoning, access to parks, walkability, and transportation.

For Land Use HIAs, the Tracking Network has

• outdoor air quality measures for ozone and fine particulate matter (PM_2.5)
• community design indicators such as motor vehicle fatalities, access to parks and schools, and types of transportation to work
• population demographics and socioeconomic measures
• asthma hospital stays, prevalence, and emergency department visits
• heart attack hospital stays
• childhood blood lead levels
• age of housing

View Land Use Diagram

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:

• more intense tropical cyclones
• more frequent and severe heat waves
• increased precipitation or drought
• more frequent heavy precipitation events (such as rain and snow)
• flooding as a result of heavy precipitation
• sea level increases
• additional air pollution (such as ozone and allergens in the air like pollen and mold)

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:

• extreme heat days and events
• heat stress hospital stays and emergency department visits
• heat vulnerability
• heat-related deaths
• asthma hospital stays, prevalence, and emergency department visits
• temperature distribution
• ozone
• population demographics and socioeconomic measures

You can read more about CDC’s climate adaptation work on our Climate and Health Program website.

View Heat and Ozone Diagram

Tracking Network data may be used to inform many other types of HIAs beyond the examples described above. For case studies and examples of different types of HIAs, see:

• Human Impact Project (interactive US map)
• UCLA Health Impact Assessment Clearinghouse

When conducting HIAs, scoping is a process that defines what the assessment will address, including 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. See examples of how Tracking data can be used in three different health impact assessments.
• 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.

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 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. The National 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 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.

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 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 compare one area or population with another.

The Tracking Program includes CDC staff and public health department staff in 25 states and 1 large city with 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 National Tracking Program or the state and local tracking programs.

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 within the project area (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 National Tracking Network and the state and local grantee 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. For example, see Mortality Benefits Associated with Reducing PM2.5(fine particle) Concentration Levels. You can generate data from the Tracking Network that provides the estimated number of deaths prevented and percent change in deaths associated with lowering PM_2.5concentration levels in air. BenMAP does not have the same spatial analysis capabilities as GIS, but it can be useful for contributing to attributable risk estimates.