MP2 Toxicity of Mixtures
255 Portland Ballroom
1:20 PM - 4:40 PM, Monday
() Shortcomings of the TEQ approach in measuring compliance with AWQC.
Ebert, E1, Samuelian, J1, Anderson, P 2, 1 AMEC, Portland, ME, USA2 AMEC, Westford, MA, USA
ABSTRACT- The use of the toxicity equivalence (TEQ) method to evaluate potential risks associated with polychlorinated dioxins and furans (PCDD/PCDF) and certain polychlorinated biphenyls (PCBs) is becoming more commonplace. It has been proposed that compliance with the ambient water quality criterion (AWQC) for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) should be measured using the total TEQ of the mixture, including all PCDD/PCDF congeners as well as the dioxin-like PCB congeners. To use such an approach, it is necessary to apply both toxicity equivalency factors (TEFs) and bioaccumulation equivalency factors (BEFs) to analytical results for water and biota. This approach to developing the AWQC and measuring compliance with it is inappropriate due to the fact that it relies on highly uncertain TEF values and oversimplifies the important site- and species-specific factors that affect BEFs. In addition, it presents substantial challenges and potential inequities in implementation and compliance. If regulatory agencies are concerned about the potential impacts of PCDD, PCDF, and PCB mixtures, then it is recommended that agencies derive criteria for the individual components of the mixtures in order avoid these important limitations.
Key words: toxicity equivalence, AWQC, bioaccumulation equivalency, TCDD