Frequent Questions

Why is the dioxin/furan Hazardous Waste Combustion Emission Standard expressed on a TEQ basis as opposed to a Total Congener basis used in the municipal waste combustor regulations?

There is a divergence in the way the standards are expressed. Dioxin/furan standards have been proposed on a TEQ basis, as this format has been recommended by the international committees and is the regulatory format for most European countries. The Agency is generally moving to expressing dioxin and furan limits in terms of TEQs, which is a more descriptive indicator of potential risk. For a rule such as this one, where it is also being used for RCRA purposes, a TEQ basis is the better choice. 

Additional Detail 
Dioxin/furan emissions are a mixture of 210 compounds (congeners). Only 17 of these compounds are considered to be toxic and the relative potency of these compounds are different from one another. The relative potencies of these compounds is considered in calculating the TEQ of dioxin/furan emissions. 

Different types of sources typically emit different types of dioxin/furan congeners, and the types of congeners emitted at a given source can change as design or operating conditions change.
 
Therefore, even though various sources may be emitting dioxin/furans at the same total congener level, the TEQ (which is indicative of potential risk) may vary dramatically. Therefore, the Agency generally believes that a TEQ-based standard is more appropriate for hazardous waste combustors than a total congener-based standard.

For more information, see http://www.epa.gov/epaoswer/hazwaste/combust/.

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