Section 6: Chemicals of Special Concern

Releases of Dioxin and Dioxin-like Compounds

Dioxin and dioxin-like compounds (dioxins) are PBTs characterized by EPA as probable human carcinogens. Dioxins are the unintentional byproducts of most forms of combustion and several industrial chemical processes. This figure shows the amount of total disposal or other releases of dioxins in grams. Releases of dioxins decreased by 43% from 2003 to 2013, but increased 23% from 2012 to 2013. This increase in 2013 was largely due to an increase in dioxins reported by one chemical manufacturer and one smelting facility. In 2013, most (73%) of the quantity released was disposed of off-site to a landfill.

TRI requires facilities to report on 17 types of dioxin (or congeners). These congeners have a wide range of toxicities. 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 toxicities can be taken into account using Toxic Equivalency Factors (TEFs), which are based on each congener’s toxicity. The total grams of each congener can be multiplied by its TEF to obtain a toxicity weight. The results can then be summed 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. Since 2010 grams-TEQ have increased by 159%, while dioxin grams released have increased by 92%. 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.

This page was published in January 2015 and uses the 2013 TRI National Analysis dataset made public in TRI Explorer in October 2014.