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Cong, These are great questions and fit in well with the fact that
PCDD/F are among the chemicals we’ve identified to spend some effort on
revising our treatment of in the near future. Here are my initial responses,
which are open to discussion and correction by the group: 1)
As with everything else, we store this data at the regional level
in pounds. Some inventories store these as grams or another smaller unit to avoid
the problem that we sometimes encounter that the values are often so small when
expressed in pounds that the 12 digit field limits in our database can cause
loss of data. For these compounds, the input we’ve gotten from
toxicologists is that even very small quantities are important and we should
not assume that if something is many orders of magnitude less than a pound that
it is insignificant. I do not believe that we are including any data as TEQs.
It’s possible that we should be and that is one reason for wanting to
revisit our approach to these 2)
Yes, the PCDD and PCDF groups represent the sum of all congeners
(by weight, not TEQ). The only exception is below. Someone correct me if I am
wrong. 3)
No. Where we can quantify the 2378 congeners alone, those
are reported in these separate categories. The PCDD/F categories should not
include those numbers to avoid double counting. Again, someone correct me if I’m
wrong. The answers above reflect how I believe we currently are dealing
with these categories, but that does not imply that this is how we should be dealing
with them. I think there is good rationale and data available to be treating these
categories differently than we do. Reviewing this, especially in light of the
EPA’s recent report, is on the to-do list for the future. Jon ~~~~~~~~~~~~~~~~~~~ Jon Dettling 734-274-5183 dettling@glc.org From: Doan, Congtru (ENE)
[mailto:Congtru.Doan@ontario.ca] Hi
Jon, We
have discussed about conventions on PCDD and PCDF few times. Could you please
let me know what conventions used by the group regarding the units and
congeners of PCDD, PCDF?
Thanks. Cong, |