Fall 2023

GIS Tools to Evaluate Environmental Justice Concerns: Uses and Limitations

By Naomi L. Slagowski, M.S., and Matthew J. Mayo, M.S., GISP, CPG, P.G.

Environmental Justice (EJ) is a growing area of interest and focus of decision-makers and community organizations across the United States (US), and the Biden-Harris Administration has spurred much EJ-related activity in the past few years (Harvard Law School, 2023).  To aid in these efforts, many tools, such as the US Environmental Protection Agency (US EPA) EJScreen, have been developed by federal and state agencies to review the complex set of stressors and demographic factors that contribute to EJ concerns for a community.  EJ tools generally share a map-based system, also referred to as a geographic information system (GIS), and data are shared between many tools.  In effect, anyone with GIS software can access the data used in the EJ tools in one centralized location (see Figure).

Environmental Justice (EJ) Tools Based on GIS

While EJ tools rely on overlapping data sources, each tool uses metrics and data sets of interest to the stakeholder and/or specific to the tool’s purpose.  For example, all prominent EJ tools incorporate environmental factors (e.g., ambient particulate matter [PM] in an area, proximity to National Priority List [Superfund] sites, or air toxics cancer risk).  In addition, some EJ tools also incorporate health factors (e.g., asthma or cancer prevalence) and, increasingly, climate change-related factors (e.g., areas at risk of sea level rise, flooding, and/or wildfires) (see Table).

Summary of Environmental Justice (EJ) Tools

EJ tools are useful because they are easy to use, provide transparency, and are publicly available.  In addition, having access to EJ tools removes the burden of high-level data analysis and modeling from community groups, agencies, or companies interested in investigating potential EJ concerns.  For example, companies that rely on EJ tools to screen areas of interest before beginning a project can potentially avoid introducing EJ-related issues, which may hold up permit applications or pause construction.  Corporate stakeholders are also interested in EJ issues near current or future industrial properties, both for community relations and environmental, social, and governance (ESG) concerns.  Because of their GIS basis, EJ tools provide a simple way for many stakeholders to view screening-level EJ data at multiple industrial sites or communities in one place.

[C]ompanies that rely on EJ tools to screen areas of interest before beginning a project can potentially avoid introducing EJ-related issues, which may hold up permit applications or pause construction.”

EJ tools have some notable limitations, as sometimes they show different levels of potential concern in the same area.  For instance, within a mile of the White House, the Climate and Economic Justice Screening Tool (CEJST) identifies only one disadvantaged census tract, while EJScreen shows multiple census block groups in the same area that exceed the 90^th national percentile for half of its thirteen EJ Indexes (see Table above).  These disparate results are driven by demographic differences – while CEJST uses income level, EJScreen also incorporates communities of color and, therefore, environmental stressors are weighted differently in these tools depending on demographics.

EJ tools have some notable limitations, as sometimes they show different levels of potential concern in the same area.”

Furthermore, EJ tools provide a high-level view of potential issues affecting an area but, with few exceptions, are not intended to be used to make specific regulatory decisions at a local level because:

• No tool captures all environmental, health, or socioeconomic factors that can affect an individual’s health;
• Non-chemical stressors, such as dietary, physical, psychological, and social risk factors, are typically qualitative and not easily incorporated into quantitative screening tools (National Research Council, 2009);
• National tools are limited to nationwide data sets, while state tools can contain additional data only available in that state and few tools incorporate local information;
• EJ tools often rely on model-based data, and models may have inherent assumptions that might not apply to all mapped areas;
• Demographic data are based on sample individuals in a geographic area not the entire population, and data are often linked to the most recent decennial census, which may be outdated (US Census Bureau, 2022); and
• Data for the EJ tools are not updated at the same frequency, thus, the various tools often display data from different years at the same geographic location.

As interest in EJ continues to grow, EJ analyses will be increasingly required by laws and regulations and/or requested by shareholders with ESG concerns.  Since EJ tools are easy to use and readily available, they provide a good information base for discussions with community groups when EJ issues arise.  As a result, EJ tools are a powerful way to view many data sets where modeling and analysis are already available, and because of their GIS basis, the results of multiple EJ tools can be readily overlaid and compared.  While EJ tools frequently use much of the same data, each tool has a specific focus; therefore, it is best to review the results of many EJ tools rather than rely on the data from just one.