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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. The vast majority of TRI releases occur in the course of routine production operations at the facility.

ReleasesHelpReleasesAny spilling, leaking, pumping, pouring, emitting, emptying, discharging, injecting, escaping, leaching, dumping, or disposing into the environment (including the abandonment or discarding of barrels, containers, and other closed receptacles) of any toxic chemical. [42 U.S.C. §11049 (8)] [40 CFR § 372.3] or disposalHelpDisposalAny underground injection, placement in landfills/surface impoundments, land treatment, or other intentional land disposal. [40 CFR § 372.3] of chemical waste into the environment occur in several ways. Facilities may release chemical waste into the air or water or dispose of it on land, per EPA regulatory requirements. Facilities may also ship (transfer) wastes that contain TRI chemicals to an off-site location for treatment or disposal. Release and disposal practices are subject to a variety of regulatory requirements designed to minimize potential exposure or 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 the EPA laws and regulations webpage.

Evaluating releases of TRI-listed chemicals can help identify potential concerns and gain a better understanding of potential risks the releases may pose. 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 necessarily 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 reading about or 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 and text that focus only on the year 2018 include all chemicals reportable for 2018, therefore, values for a 2018-only analysis may differ slightly from results for 2018 in a trend analysis.

The following graph shows the total disposal or other releases of TRI chemicals (also referred to as “total releases”), including on-site disposal to land, discharges to water, and releases to air, and off-site transfers for disposal or release.


Note: For comparability, trend graphs include only those chemicals that were reportable to TRI for all years presented.

From 2007 to 2018:

  • Total disposal or other releases of TRI chemicals decreased by 9%.
    • Excluding the metal mining sector, releases decreased by 34%.
    • 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.
  • Air releases decreased 56%, surface water discharges decreased 18%, and off-site disposal decreased 22%.
  • The number of facilities reporting to the TRI Program declined by 8% overall, although the count has remained relatively steady since 2010.

From 2017 to 2018:

  • Total disposal or other releases decreased by 3%.
    • On-site land disposal decreased by 6%, which is the main driver for the decrease in total releases. There was little change in on-site air releases or on-site surface water discharges, while off-site disposal increased by 11%.

Releases in 2018

Use the interactive chart below to explore how total releases of chemicals that occurred in 2018 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 comprised 75% of total releases.


Note: In this figure, metals are combined with their metal compounds, although metals and compounds of the same metal are 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 47% of releases (1.80 billion pounds), which were primarily in the form of on-site land disposal. Learn more about this sector in the Metal Mining profile.


This page was published in February 2020 and uses the 2018 TRI National Analysis dataset made public in TRI Explorer in November 2019.

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