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TRI National Analysis

Releases of Chemicals

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Helpful Concepts

What is a release?

In the context of TRI, a “release” of a chemical generally refers to a chemical that is emitted to the air, discharged to water, or disposed of in some type of land disposal unit.

Disposal or other releases of Toxics Release Inventory (TRI) chemicals into the environment occur in several ways. Chemicals may be disposed of on a facility’s property by being released to the air, water or land. Facilities may also ship (transfer) wastes that contain TRI chemicals to an off-site location for treatment or disposal. Most disposal or other release practices are subject to a variety of regulatory requirements designed to minimize potential harm to human health and the environment. To learn more about what EPA is doing to help limit the release of TRI chemicals into the environment, see EPA's laws and regulations webpage.

Evaluating releases of TRI-listed chemicals can help identify potential concerns and gain a better understanding of potential risks that may be posed by the releases. This evaluation can also help identify priorities and opportunities for government and communities to work with industry to reduce chemical releases and potential associated risks. However, it is important to consider that the quantity of releases is not an indicator of health impacts posed by the chemicals. Human health risks resulting from exposure to TRI chemicals are determined by many factors, as discussed further in the Hazard and Potential Risk of TRI Chemicals section.

Many factors can affect trends in releases at facilities, including production rates, management practices, the composition of raw materials used, and the installation of control technologies.

As with any dataset, there are several factors to consider when using the TRI data. Key factors associated with data presented are summarized in the Introduction. For more information see Factors to Consider When Using Toxics Release Inventory Data. Also note that the list of TRI chemicals has changed over the years. For comparability, trend graphs include only those chemicals that were reportable for all years presented. Figures that focus only on the year 2017 include all chemicals reportable for 2017, therefore, values for a 2017-only analysis may differ slightly from results for 2017 in a trend analysis.

The following graph shows the disposal or other releases of TRI chemicals, including on-site disposal to land, water, and air, and off-site transfers for disposal.


From 2007 to 2017:

  • Total disposal or other releases of TRI chemicals decreased by 7%.
    • Excluding the metal mining sector, releases decreased by 37%.
    • Reduced hazardous air pollutant (HAP) emissions, such as hydrochloric acid, from electric utilities were the most significant contributor to the decline, with additional air emission reductions from the chemical and paper manufacturing sectors.
  • On-site air releases (down 57% from 2007), on-site surface water discharges (down 20% since 2007), and off-site releases (down 31% since 2007) declined during this 10-year period.
  • The number of facilities reporting to the TRI Program declined by 8% overall, although the count has remained relatively steady since 2010.

From 2016 to 2017:

  • On-site air releases and on-site surface water discharges decreased while off-site disposal increased, each with under 5% change. Total releases to the environment increased by 13%, driven by the 21% increase (433 million pounds) in on-site land disposal.

Releases in 2017

Use the interactive chart below to explore how total releases of chemicals that occurred in 2017 are associated with different industry sectors, specific chemicals, and geographies. Visit the full TRI National Analysis Qlik dashboard to explore even more information about releases of chemicals.

Releases by Chemical

Release quantities of 8 chemicals comprise 76% of total releases.


Note: In this figure, metals are combined with their metal compounds, although metals and compounds of the same metal are usually listed separately on the TRI list (e.g. lead is listed separately from lead compounds). Percentages may not sum to 100% due to rounding.

Releases by Industry

The metal mining sector accounted for 50% of releases (1.95 billion pounds), which were primarily in the form of on-site land disposal.


This page was published in March 2019 and uses the 2017 TRI National Analysis dataset made public in TRI Explorer in October 2018.

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