TRI National Analysis

Dioxins Releases Trend in the 2015 TRI National Analysis

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This graph shows the trend in the pounds of dioxin and dioxin-like compounds disposed of or otherwise released.


Dioxin and dioxin-like compounds (dioxins) are Persistent, Bioaccumulative, and Toxic chemicals (PBTs) characterized by EPA as probable human carcinogens. Dioxins are the unintentional byproducts of many forms of combustion and several industrial chemical processes. TRI requires facilities to report on 17 types, or congeners, of dioxin. Congener information was first collected in 2010.

These congeners have a wide range of toxic potencies. The mix of dioxins from one source can have a very different level of toxicity than the same total amount, but different mix, from another source. These varying toxic potencies can be taken into account using Toxic Equivalency Factors (TEFs), which are based on each congener’s toxic potency. EPA multiplies the total grams of each congener reported by facilities by the associated TEF to obtain a toxicity weightHelptoxicity weightThis weight is a proportional numerical weight applied to a chemical based on its toxicity. The toxicity of a chemical is assessed using EPA-established standard methodologies. For each exposure route, chemicals are weighted based on their single, most sensitive adverse chronic human health effect (cancer or the most sensitive noncancer effect). In the absence of data, the toxicity weight for one pathway is adopted for the other pathway. The range of toxicity weights is approximately 0.02 to 1,400,000,000., and sums all congeners for a total of grams in toxicity equivalents (grams-TEQ). Analyzing dioxins in grams-TEQ is useful when comparing disposal or other releases of dioxin from different sources or different time periods, where the mix of congeners may vary.

From 2005 to 2015:

  • Releases of dioxins increased by 5%, with a significant decrease in on-site land disposal and increase in off-site disposal or other releases.

From 2010 to 2015:

  • Since 2010, grams-TEQ increased by 222%, while dioxin grams released increased by 121%.
    • This suggests that releases of the more toxic congeners have increased at a faster rate than releases of dioxins overall, causing grams-TEQ of dioxins to increase at a higher rate than overall grams.

From 2014 to 2015:

  • Releases of dioxins increased by 1%, but grams-TEQ decreased by 11%.
  • In 2015, most (60%) of the quantity released was disposed of off-site.

This page was published in January 2017 and uses the 2015 TRI National Analysis dataset made public in TRI Explorer in October 2016.

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