TRI Suit Extended Pending EPA Discussions on PBT Reporting
Parties to a federal lawsuit challenging EPA's new reporting requirements for releases of 17 persistent bioaccumulative toxic (PBT) chemicals have agreed to defer court briefing while discussions about supplemental reporting continue with the agency. The plaintiffs, including CRE Board Member Jim Tozzi, have agreed to postpone their summary judgment filing until November 1, 2001 in the hope that talks with the agency may yield an agreement on broader use of toxic equivalents or "TEQ" methodology under the agency's new reporting rule. In another development, EPA stated in a letter to Congress that the agency is "working in partnership with the American Chemistry Council and the Chlorine Chemistry Council" to provide improved public access to TEQ data.
The Value of TEQ Reporting
There are two fundamental methods used to specify a given quantity of dioxin. These are the TM-17 (Total Mass of 17 dioxin family member compounds) and the TEQ (Toxic Equivalent) methods. While communicating amounts of most chemical compounds is a simple matter of measuring and reporting their masses in grams, the case of dioxin is complicated by the fact that "dioxin" is not purely one chemical compound. Dioxin always occurs as a mixture of its family member compounds. The exact composition of the mixture depends upon the physical and chemical conditions of its formation. Moreover, the 17 individual dioxin family member compounds of concern vary up to 10,000-fold in toxicity. Thus, the toxicity of a gram of dioxin could vary considerably depending on the toxicities of the individual compounds that compose the dioxin mixture.
While the TM-17 method specifies the total mass, in grams, of a dioxin mixture, the TEQ method is designed to communicate the toxicity of the mixture in grams-TEQ. Within the TEQ method, "Toxic Equivalency Factors" (TEFs) are assigned to each of the individual dioxin family members. TEFs are order of magnitude estimates of toxicity of individual compounds relative to 2,3,7,8-TCDD. The TEF of 2,3,7,8-TCDD is defined as one. Nearly all other family member compounds have TEFs less than one, and proportional to their toxicities relative to that of 2,3,7,8-TCDD. TEFs may be thought of as "weighting factors" in calculating the number of grams-TEQ of a dioxin mixture. Using the TEQ method, the masses of individual dioxin compounds in a mixture are multiplied by their respective TEF weighting factors and these figures are then summed to obtain a gram-TEQ total.
The value of TEQ reporting of dioxin quantities (e.g., annual TRI reporting of emissions, source reductions, or quantities disposed) can be demonstrated by comparing reported TEQ masses -- of one facility's emissions, for example -- from one year to the next. Given the information that the number of grams-TEQ from a particular dioxin source had risen over the course of a year from 14 to 35, one could reasonably conclude that the toxicity of emissions from that source had increased. However, the same quantity reported by the TM-17 method would conceal any change in toxicity of the mixture. For this reason, TEQ reporting of dioxin amounts offers valuable information that cannot be imparted by the TM-17 method.