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Jon, Tom: Thank for your responses. Tom, I interpret TEQ as a unit not a pollutant.
Based on this, I believe you mean “all dioxins, furans” have their
own CAS number … Like other pollutants, the emission units for congeners are
lb, gram … However, the unit “TEQ” is commonly used for PCDD,
PCDF groups. One can calculate TEQ values for each congener of each group then add
them up and represent the total as a single pollutant group (PCDD or PCDF) with
TEQ unit. So if one knows the emission for each
congener, he/she can always represent the PCDD, PCDF in any units (lb, gram,
TEQ). Problem arises when the unit of available emission of the group is in
TEQ. It is not possible to convert it back to the natural unit. My question is that should we consider additional
unit “TEQ” to RAPIDS for the purpose of making use of PCDD, PCDF
numbers that are in TEQ. The consequence of adding this new unit is having two
units for PCDD, PCDF! What do you mean by saying “The Dioxin and
Furan groups exclude the TEQs” ? You subtract the total emission of the
congeners from the total or did not total up the emissions of the congeners to
produce PCDD, PCDF or just simply saying you do not use “TEQ” unit
in PCDD, PCDF. Thanks. Cong, From: Tom
Velalis [mailto:tom.velalis@epa.state.oh.us] Jon I believe you
provided an accurate response to Cong's question. Also, that is the
arrangment used by
NEI. Attached is groups exclude
the TEQs. The Explanation is provided in the
HAP_CATEGORY_NAME. The TEQs have their own CAS number and enjoy their
own space in the pollutants table. As far as
units go, I have converted all Webfire units into unit of mass,
pounds (except radiocative units). Tom. 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: 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, |