Air & Water Quality – Wastewater Discharge
This indicator reports the RSEI modeled Toxic Concentrations at stream segments within 500 meters, divided by distance in kilometers (km). It quantifies a block group’s relative risk of exposure to pollutants in downstream water bodies. Areas with higher wastewater discharge values are placed higher in percentile (national ranking). The percentile could be interpreted as, for example, for a place at the 80th percentile nationwide, 20% (i.e., 100 minus the percentile) of the U.S. population lives in a block group that has a higher value.
The EJ Index for Wastewater Discharge is a combination of this environmental indicator and the Demographic Index (the average of percent low-income and percent people of color).
Data are acquired from EPA’s EJScreen dataset, 2024.
Source
Source Description
EJScreen is an EPA’s environmental justice mapping and screening tool that provides EPA with a nationally consistent dataset and approach for combining environmental and demographic socioeconomic indicators. An EJ index combines demographic factors with a single environmental factor. For example, the EJ index for traffic proximity is a combination of the following populations residing in the Census block group:
- The traffic proximity indicator;
- The low-income population;
- The people of color populations.
Note that an EJ index does not combine various environmental factors into a cumulative score — each environmental indicator has its own EJ index.
The EJ index is higher in block groups with large numbers of mainly low-income and/or people of color residents with a higher environmental indicator value.
For more information, please visit the EJScreen website.
Methodology
This indicator reports the RSEI modeled Toxic Concentrations at stream segments within 500 meters, divided by distance in kilometers (km). It quantifies a block group’s relative risk of exposure to pollutants in downstream water bodies.
To place higher emphasis on stream reaches with higher toxicity-weighted pollutant concentrations, the toxicity-weighted value for all stream reaches within 500 meters of a census block centroid is divided by the distance in meters to the census block centroid to create a weighted proximity value indicating a block’s risk of exposure to pollutants in the stream reaches.
The results are aggregated to the parent block group using the population weight for each block within the block group. The population weights come from the 2010 Census. Minor adjustments are needed to crosswalk Census 2010 blocks and 2019 blocks. Based on the block group data, CARES estimated the values for all other geographic levels using total population (ACS 2018-22) and the technique of Population-weighted Small Area Estimate. Wastewater discharge source is provided by EPA’s Office of Pollution Prevention and Toxics (OPPT) on March 15, 2021 from 2019 Risk-Screening Environmental Indicators (RSEI) modeled results.
The percentile in EJScreen is reported as what percent of the U.S. population lives in a block group that has a lower value (or in some cases, a tied value).
The relevant EJ Index is calculated as:
where Normalized Environmental Indicator is the percentile of the particular environmental indicator source data.
For more information about this indicator or the methodology of EJScreen, please refer to the EJScreen Technical Documentation.
This indicator is available at the following subscription levels:
- Premium (currently viewing this indicator and report combination)