Frequent Questions about Power Plants and Neighboring Communities
On this page:
- What is the purpose of Power Plants and Neighboring Communities?
- What is Power Plants and Neighboring Communities?
- How do I use the Power Plants and Neighboring Communities mapping tool?
- What are the included socioeconomic indicators?
- What is “EJScreen”?
- What are the demographic indexes?
- Why is a three-mile radius around power plants selected to represent the neighboring communities?
- How is the summary information determined for the surrounding area within three-miles of each plant?
- What is a percentile and why is it used?
- Why are areas at or above the 80th percentile highlighted?
- What are the data sources and what years do the data represent?
- How are the power plant emissions determined?
- Is data is available for download?
- Are there limitations using the data to assess whether certain communities carry a greater environmental health burden?
- How does EPA expect to use this tool, or expect state and local governments to use it?
- How do I cite Power Plants and Neighboring Communities?
- Can I provide feedback?
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1) What is the purpose of Power Plants and Neighboring Communities?
The purpose is to reduce barriers to access publicly available data. EPA has a wealth of high-quality data on power plant operation and emissions through the CAPD Power Sector Emissions Data and the Emissions & Generation Resource Integrated Database (eGRID) and also has a tremendous amount of environmental justice related information through EJScreen. The Power Plants and Neighboring Communities webpage and associated mapping tool combine power plant data with the EJScreen data in order to present the socioeconomic characteristics of communities within three miles of power plants.
The data is presented through interactive maps and graphs where users can both drill down to a specific area of interest, like where they live, or see a comprehensive view of the socioeconomic characteristics of all communities adjacent to power plants in the United States.
2) What is Power Plants and Neighboring Communities?
Power Plants and Neighboring Communities (PPNC) is an interactive webpage and mapping tool that presents power plant data with an environmental justice focus. For every fossil fuel-fired power plant in the U.S., PPNC provides information on emissions (e.g., SO2, NOX, CO2) and summarizes the socioeconomic characteristics of the communities around each plant. The socioeconomic information (i.e., people of color, low-income, unemployment rate, limited English speaking, less than high school education, under age 5, and over age 64) is taken directly from EPA’s EJScreen. Summary information is presented through interactive graphs and users can filter plants based on plant characteristics or socioeconomic characteristics of those people living near power plants. And the data is downloadable.
3) How do I use the Power Plants and Neighboring Communities mapping tool?
You can interact with the map by using both the layers and filters. The layers are displayed on the right side of the map. A couple of the layers are visible when the map is loaded, but most are not visible until you toggle them on. You can turn on the visibility of a layer by clicking the “eye” icon to the left of the layer name. Some layers are not visible until you zoom in.
You can also filter the map results according to different parameters (e.g., power plant fuel type, emissions) to help answer questions about power plant characteristics and surrounding community socioeconomic characteristics.
See the Power Plants and Neighboring Communities Training page for more details. To learn more about navigating online maps, visit the Finding and Navigating Maps in ArcGIS Online website for a short video and interactive sample map.
4) What are the included socioeconomic indicators?
The socioeconomic indicators included in the Power Plants and Neighboring Communities information are people of color, low-income, unemployment rate, limited English speaking, less than high school education, under age 5, and over age 64. These socioeconomic indicators can provide a very general indicator of a community’s potential susceptibility to environmental pollution.
These socioeconomic indicators are consistent with the demographic indicators used in EJScreen. More information is available in this Overview of socioeconomic indicators in EJScreen. Detailed information about the socioeconomic indicators, including data sources, can be found in Section 2, "Overview of Data in EJScreen", of the Technical Documentation for EJSCREEN.
5) What is “EJScreen”?
EJScreen is an environmental justice mapping and screening tool that provides a nationally consistent dataset and approach for combining environmental and demographic indicators. The frequent questions about EJScreen page has more information.
6) What are the demographic indexes?
The demographic index is based on the average of two demographic indicators: low-income population and people of color. Minority and low-income populations were explicitly named in EO 12898, which is intended to focus federal attention on the environmental and human health effects of federal actions on minority and low-income populations with the goal of achieving environmental protection for all communities. See EPA’s definition of low-income population and people of color.
The demographic index counts each indicator as adding to overall potential susceptibility of the population and assumes the two demographic indicators have equal and additive impacts.
The supplemental demographic index is based on the average of five socioeconomic indicators; low-income, unemployment, limited English, less than high school education, and low life expectancy (which is a health dataset).
More information can be found in the “Overview of Data in EJScreen” section 2 of the Technical Documentation for EJScreen.
7) Why is a three-mile radius around power plants selected to represent the neighboring communities?
A three-mile radius is consistent with environmental justice literature and studies, including the National Association for the Advancement of Colored People (NAACP) report " Coal Blooded: Putting Profits Before People”, EPA’s “EJ Screening Report for the Clean Power Plan”, Toxic Wastes and Race and Toxic Wastes and Race at Twenty (which uses various buffer sizes including 5 kilometers, or 3.1 miles), and Historical red-lining is associated with fossil fuel power plant siting and present-day inequalities in air pollutant emissions. More information about buffers can be found in the “Buffer Reports” section of the Technical Documentation for EJScreen.
8) How is the summary information determined for the surrounding area within three-miles of each plant ?
EPA uses methodology consistent with EJScreen to calculate the summary information for the areas around plants (i.e., buffers). The socioeconomic summary for a buffer is designed to represent the average resident within the buffer, and also provides an estimate of the total population residing in the buffer. U.S. Census defined block groups and blocks are used to determine the summary socioeconomics. Some block groups will be partly inside and partly outside the buffer, and the buffer analysis must estimate how much of each block group’s population is inside the buffer.
To provide the most accurate counts that are currently feasible for this mapping tool, an approach based on Census block internal points is used. The methodology estimates the fraction of the Census block group population that is inside the buffer by using block-level population counts from Census 2010. These blocks provide data about where residents are at a higher resolution than block groups. Each block has an internal point defined by the Census Bureau, and the entire block population is counted as inside or outside the buffer depending on whether the block internal point is inside or outside.
The calculation of a value for the buffer is essentially the population-weighted average of the indicator values in the blocks included in the buffer, where each block uses the indicator values of the block group containing it. A block group is weighted based on the fraction of the U.S. Census American Community Survey (ACS) block group population that is considered in the buffer. That fraction is estimated as the Census block population divided by the Census block group population.
Detailed information about calculating data for surrounding buffers can be found in section 6, “Buffer Reports”, of the Technical Documentation for EJScreen.
9) What is a percentile and why is it used?
A percentile is a relative term. Percentiles are a way to see how local residents in a given community compare to everyone else in the United States. Instead of just showing numbers out of context, percentiles let you compare a community to the rest of the nation. The national percentile tells you what percent of the U.S. population has an equal or lower value.
For example, if an area is 50% people of color and is at the 70th national percentile, this means that 50% of the area’s population is people of color, and that is an equal or higher percentage of people of color than where 70% of the U.S. population lives.
This EJScreen frequent question gives more details on the relationship between raw data and percentile and the Technical Documentation for EJScreen gives more information in section 4, "Technical Details on Percentiles".
10) Why are areas at or above the 80th percentile highlighted?
EPA uses the 80th percentile as a starting point for the purpose of identifying geographic areas that may warrant further consideration, analysis, or outreach. Communities above the 80th percentile for any socioeconomic indicators are communities where a particular socioeconomic indicator is at a level equal or higher than where 80% of the U.S. population lives (i.e., 80th percentile nationally). The use of the 80th percentile is consistent with EJScreen. More information about the use of the 80th percentile in EJScreen can be found in this frequent question and in section 4, " Technical Details on Percentiles" of the Technical Documentation for EJScreen.
11) What are the data sources and what years do the data represent?
The data is updated annually to the lasted available data. The following table presents the data source, source website, and the year or version of data used.
| Data Source | Source Website | Data Year or Version |
|---|---|---|
| eGRID | Emissions & Generation Resource Integrated Database (eGRID) | US EPA | 2022 |
| CAPD Power Sector Data | Clean Air Power Sector Programs | US EPA | 2023 |
| EJScreen | EJScreen: Environmental Justice Screening and Mapping Tool | US EPA | Census Bureau’s ACS 2018-2022 5-year Summary accessed via EJScreen Version 2.3 |
EJScreen combines data from many different sources, including the U.S. Census Bureau’s American Community Survey (ACS). For more information on the ACS data year and data years for the other data sources compiled in EJScreen, go to the Overview of Environmental Indicators in EJScreen page.
The Power Plants and Neighboring Communities Map webpage and the Announced Power Plant Retirement map pages provide additional details on data years and data sources.
12) How are the power plant emissions determined?
For a subset of power plants (generally, those that are above 25 MW nameplate capacity), the SO2, NOX, and CO2 emissions are directly reported to EPA through CAPD’s Power Sector Emissions data and the PM2.5 data is reported under EPA’s National Emissions Inventory (NEI).
For the remainder of power plants, emissions are calculated by multiplying the operating data (i.e., heat input) reported directly to EIA from the power plants by EPA developed emission factors. The emission factors are either derived from like-kind units, when available, or from EPA’s AP-42: Compilation of Air Emissions Factors.
More information on determination of emissions and emission rates can be found in the eGRID Technical Guide.
13) Is data is available for download?
Yes, the data is available for download in an Excel spreadsheet or CSV file . This spreadsheet includes:
- Emissions and operating data from eGRID;
- Emissions data from EPA’s Power Sector Emissions Data (when available); and
- EJScreen data on socioeconomic indicators.
14) Are there limitations using the data to assess whether certain communities carry a greater environmental health burden?
Yes, the underlying EJScreen data presented has its own limitations and caveats, explained in the EJScreen frequent questions and on this webpage. The Power Plants and Neighboring Communities mapping tool only presents power plant locations and does not include information regarding other types of facilities that may be located near the same communities and that may contribute to the environmental impacts on public health.
Additionally, it’s important to note that impacts of power plant emissions are not limited to a three-mile radius because pollutants can travel over long distances. For this reason, there is a level of uncertainty that must be considered when looking at community demographics and power plant pollution. EPA is exploring additional methods of addressing these uncertainties, but the primary purpose of this tool is to illustrate the characteristics of communities closest to power plants.
15) How does EPA expect to use this tool, or expect state and local governments to use it?
EPA created this resource to inform and assist all stakeholders with improved access and integration of EPA’s emissions and EJScreen data. This resource can enhance the public’s understanding of the potential impacts of power plants on their communities. We encourage state, local and tribal governments to employ all of the tools and information at their disposal to make the best decisions in protecting the environment and public health. As such, we welcome use of the Power Plants and Neighboring Communities website by state, local and tribal governments if it proves useful in their environmental protection efforts.
16) How do I cite Power Plants and Neighboring Communities?
The following citation for Power Plants and Neighboring Communities is suggested:
United States Environmental Protection Agency (EPA). 2022. “Power Plants and Neighboring Communities (PPNC), 2022” Washington, DC: Office of Atmospheric Programs, Clean Air Markets Division. Available from EPA’s PPNC web site.
17) Can I provide feedback?
Yes, we greatly appreciate feedback! Please use this form or email.
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