Water Releases
TRI chemicals released into streams or other water bodies are referred to as “water releases” or Surface Water DischargesIncludes discharges to streams, rivers, lakes, oceans and other bodies of water. These discharges come from contained sources, such as industrial process outflow pipes or open trenches. Facilities must identify the name of each water body into which the TRI chemical is being discharged. Releases of TRI chemicals due to runoff, including stormwater runoff, are also reportable in this category.. They are regulated by the Clean Water Act, which requires facilities that discharge pollutants into surface water to obtain permits under the National Pollutant Discharge Elimination System (NPDES).
The following graph shows the 10-year trend in the amount of TRI chemicals directly released into water bodies.
From 2013 to 2022:
- Discharges of TRI chemicals into surface water decreased by 18 million pounds (-9%). Most of this decline was due to reductions in releases of nitrate compounds.
- Nitrate compounds are often formed as byproducts during wastewater treatment processes such as neutralization of nitric acid, or when nitrification takes place to meet standards under EPA’s effluent guidelines.
In 2022:
- Nitrate compounds alone accounted for 90% of total releases of TRI chemicals to water.
- Many sectors release nitrate compounds, but facilities in the food manufacturing sector released the most.
The following graph shows the 10-year trend in RSEI Scores for TRI chemicals directly released into water bodies.
- While total water releases have been fairly steady from 2013 through 2022, associated RSEI Scores have fluctuated substantially. Nitrate compounds account for most water releases, and the quantity of nitrate compounds released has not changed significantly from year to year. Although nitrate compounds can cause serious problems in the environment like eutrophication, their relatively low toxicity means they do not impact RSEI Scores as much as more toxic chemicals. Relatively small changes in release quantities of more toxic chemicals can have large impacts on RSEI Scores but little impact on the trend in total pounds released.
- The largest chemical contributors to the changes RSEI Scores for water releases between 2013 and 2022 were arsenic compounds and mercury compounds.
- For a complete, step-by-step description of how EPA’s RSEI model derives RSEI Score values for surface water discharges of TRI chemicals, see “Section 5.4: Modeling Surface Water Releases” of EPA’s Risk-Screening Environmental Indicators (RSEI) Methodology.
- For general information on how RSEI Scores are derived, see Potential Risks from TRI Chemicals.
Nitrate compounds are a group of chemicals with relatively low toxicity to humans compared to many other TRI compounds. However, these compounds have the potential to cause increased algal growth leading to eutrophication in the aquatic environment. See EPA’s Nutrient Pollution webpage for more information about the issue of eutrophication.
This page was published in March 2024 and uses the 2022 TRI National Analysis dataset made public in TRI Explorer in October 2023.