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TRI National Analysis

Dioxins Releases Trend

Helpful Concepts

Toxic Equivalent Factor (TEF)

Each dioxin congener is assigned a TEF that provides that compound’s toxicity relative to the most toxic compound in the dioxin and dioxin-like compounds category.

Toxic Equivalency (TEQ)

A TEQ is calculated by multiplying the reported grams released of each congener by its corresponding TEF and summing the results, referred to as grams-TEQ.

Dioxin and dioxin-like compounds (“dioxins”) are persistent bioaccumulative toxic (PBT) chemicals characterized by EPA as probable human carcinogens. Dioxins are the byproducts of many forms of combustion and several industrial chemical processes.

TRI requires facilities to report data on the 17 individual members, or congeners, that make up the TRI dioxin and dioxin-like compounds category. While each of the dioxin congeners causes the same toxic effects, they do so at different levels of exposure, as indicated by their varying toxic potencies. As a result, the mix of dioxins from one source can have a very different toxic potency than the same total amount of a different mix of dioxins from another source.

EPA accounts for the differences in toxic potency of the dioxin congeners using Toxic Equivalency (TEQ) values. TEQs help the public better understand the toxicity of dioxins releases and are useful when comparing disposal or other releases of dioxins from different sources or different time periods, where the mix of congeners may vary.

This graph shows the trend in the grams of dioxins disposed of or otherwise released by TRI-reporting facilities from 2010 to 2019. Note that the dioxins chemical category is reported to TRI in grams while all other TRI chemicals are reported in pounds. A shorter timeframe is presented for the dioxins release trend than for other trend graphs because of the limited availability of TEQ information prior to 2010.


From 2010 to 2019:

  • Dioxin releases increased by 157%. This increase was largely driven by three facilities that together released 67% of all TRI-reported dioxins.
    • Increases in off-site releases of dioxins were largely driven by the same three facilities, two basic organic chemical manufacturing facilities and one smelting and refining facility.
    • Toxicity-equivalents (grams-TEQ) increased by 43%, indicating that releases of the less potent dioxin congeners increased more than the releases of the more potent dioxin congeners from 2010 to 2019.

From 2018 to 2019:

  • Releases of dioxins increased by 9%.
    • On-site disposal to land increased by 57% and was driven by two facilities. One of these facilities is in the primary metals sector and regularly reports large year-to-year variance in its releases of dioxins. The other is a hazardous waste management facility, which reported receiving a dioxin-contaminated debris stream in 2019.
    • Toxicity-equivalents (grams-TEQ) increased by 2%.
  • In 2019, most of the TRI-reported dioxin quantity released was disposed or otherwise released off site (54%) or disposed of on site to land (44%).

This page was published in January 2021 and uses the 2019 TRI National Analysis dataset made public in TRI Explorer in October 2020.

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