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RE: tox values for PCB congeners
Anne,
Thanks for sending this information. Understanding the risks related to
these emissions is the ultimate goal, so it's important to have input of
this kind.
As I'm sure you know, there are many challenges in speciating emissions a
class of chemicals such as PCBs or PCDD/Fs. Including codes for congeners
and/or homologue groups in the system is only one step. The larger
constraint is having information on the relative content of various
homologues or congeners in emissions of a given type. Without this
information, it is not possible to produce accurate speciated PCB emissions,
even if one were able to do the requisite work of entering the codes into
the system, etc. The rationale for including the set of codes we did at this
time is that we had an information source presenting emissions at this level
of specificity.
Roy's point is a good one. I think the important point is not that
homologue-level speciation is useless as much as it is that congener-level
speciation would be much more useful. We will continue to work toward that
as information becomes available allowing us to do so.
All the best,
Jon
______________________
Jon Dettling
Great Lakes Commission
734-971-9135
dettling@glc.org
-----Original Message-----
From: owner-airtoxics@great-lakes.net
[mailto:owner-airtoxics@great-lakes.net] On Behalf Of
Pope.Anne@epamail.epa.gov
Sent: Thursday, January 18, 2007 6:59 AM
To: airtoxics@great-lakes.net
Subject: Fw: tox values for PCB congeners
Jon,
I have added these additional pollutants to the NEI pollutant code
table, but you may want to read the message from Dr. Smith below. He
maintains the file with the UREs and RFCs that we use in NATA. His
point is that without specific congeners of PCBs, it will not matter in
risk assessment. So it may create more work for GLC to maintain these
pollutants rather than reporting PCBs as a group unless you revised the
list of PCBS to include congeners rather than homologues.
anne
----- Forwarded by Anne Pope/RTP/USEPA/US on 01/18/2007 06:55 AM -----
Roy
Smith/RTP/USEPA/
US To
Anne Pope/RTP/USEPA/US@EPA
01/17/2007 10:02 cc
AM
Subject
Re: tox values for PCB congeners
(Document link: Anne Pope)
Hi, Anne:
Happy new year to you, too!
Actually, most of the proposed additions are homologs, not congeners.
On that list, only 2,4,4'-tri-, 2-mono-, and deca- are congeners. None
of the three has any information that would support a different URE.
The rest (i.e., homologs) are mixtures of congeners with the same level
of chlorination, but with the chlorines at different positions. There
is some information that would let us use different UREs for some of
these, but it's not possible unless you know the exact compounds within
the homologous group. For example, 2,2',4,6,6'-pentachlorobiphenyl
would use the generic URE for PCBs, but we could assign a different URE
to 2,3,3',4,4'-pentachlorobiphenyl. In other words, the pattern of
chlorine substitution is critical to the process.
The bottom line is if the requestors have any congener-specific data for
these homologous mixtures (e.g., exactly what congeners are included in
"total heptachlorobiphenyls), then we may be able to do something.
Otherwise there's probably no alternative to using the same old PCB URE,
which makes me wonder why they want to subcategorize.
Best,
Roy
_______________
Roy L. Smith, Ph.D.
Office of Air Quality Planning & Standards (C539-02)
US EPA, RTP, NC 27711
(919) 541-5362
Anne
Pope/RTP/USEPA/U
S To
Roy Smith/RTP/USEPA/US@EPA
01/10/2007 08:36 cc
AM Ted Palma/RTP/USEPA/US@EPA
Subject
tox values for PCB congeners
Roy
Happy New year......
Here is list of PCB congeners that Great Lakes States wanted added to
the NEI . Will the UREs be different for each PCB congener or will we
use the PCB URE that we used in 99 NATA? Thanks- for looking into the
list.
anne
CAS# Pollutant
7012-37-5 2,4,4'-Trichlorobiphenyl
2051-60-7 2-Monochlorobiphenyl
2051-24-3 Decachlorobiphenyl
2050-68-2 Dichlorobiphenyl
28655-71-2 Heptachlorobiphenyls, Total
26601-64-9 Hexachlorobiphenyls, Total
25429-29-2 Pentachlorobiphenyls, Total
26914-33-0 Tetrachlorobiphenyls, Total
thanks anne
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