Reading it in a bit more detail, I understand that it comes from the fact that the oral ID is not based on minimal risk. The logic appears to be as follows:
1. You should use minimal risk to derive ID.
2. However, if a guideline has already been produced for another UK regulatory regime, and this is higher than the contam land ID based on min. risk, then you use the higher value as it would be disproportionate to use the lower one.
3. This is the case for As oral ID.
4. However, the inhal ID is based on min. risk.
5. If you mix (ie integrate) the non-min. risk and the min. risk approaches, the non-min risk portion drags the SGV back down (disproportionately); thereby going against the ethos of item 2 above.
6. Therefore, the SGV is based on the oral pathway and the inhal pathway is ignored.
7. This is deemed to be OK because the contribution to intake by inhal is quite small.
Regards,
Kevin Privett.
Dr Kevin Privett
Geo-Environmental Associate
Hydrock
Over Court Barns, Over Lane, Almondsbury, Bristol BS32 4DF
Tel:+44 (0)1454 619 533 Fax:+44 (0)1454 614125
Cell phone: +44 (0)7799 430870
Email: [log in to unmask]
-----Original Message-----
From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Paul Quimby
Sent: 13 May 2009 09:45
To: [log in to unmask]
Subject: Re: New Soil Guideline Values - Arsenic, Nickel......
Will,
I am not sure arsenic has been derived that way in the model. It says
on page four that SGV based on comparison of oral and dermal exposure
routes with the oral ID only. Therefore, by looking at the oral HCV
only you get 32.4mg/kg for residential (I assume rounded down by the EA
to 32mg/kg).
Of more interest maybe is the justification for not using the inhalation
HCV (such as the killer dust pathway), based on the low exposure
contribution (<0.1%), even though the risk when taking account
inhalation tox is about 28%. This could be used for contaminants where
inhalation is not a primary pathway and inhalation effects not of
primary concern
Nickel SGV for example has not been done this way. It has a low
combined contribution for inhalation, but the effects of inhalation are
separate to other pathways and therefore treated independently.
Interesting times :)
Paul
Dr Paul Quimby
Senior Environmental Consultant
www.thelkgroup.com
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-----Original Message-----
From: Contaminated Land Management Discussion List
[mailto:[log in to unmask]] On Behalf Of Wills
Gareth
Sent: 12 May 2009 16:03
To: [log in to unmask]
Subject: Re: New Soil Guideline Values - Arsenic, Nickel......
The EA have made some strange decisions...
To replicate the values, the arsenic SGV is based on comparison of oral,
dermal and inhalation exposure with the oral ID (NOT inhalation ID).
For nickel, it's more confusing. Residential and commercial SGV are
based on comparison of inhalation exposure with inhalation TDI ONLY.
Allotments bsaed on comparison of oral, dermal and inhalation exposure
against oral TDI ONLY.
Phew.
Gareth Wills
Project Manager, Communities
44-(0)117 9339 335
Think before you print
-----Original Message-----
From: Contaminated Land Management Discussion List
[mailto:[log in to unmask]] On Behalf Of Kevin
Privett
Sent: 12 May 2009 16:03
To: [log in to unmask]
Subject: Re: New Soil Guideline Values - Arsenic, Nickel......
I don't like to mention this, but I cannot replicate these values with
the data given in the SGV reports.
Regards,
Kevin Privett.
Dr Kevin Privett
Geo-Environmental Associate
Hydrock
Over Court Barns, Over Lane, Almondsbury, Bristol BS32 4DF
Tel:+44 (0)1454 619 533 Fax:+44 (0)1454 614125 Cell phone: +44 (0)7799
430870
Email: [log in to unmask]
-----Original Message-----
From: Contaminated Land Management Discussion List
[mailto:[log in to unmask]] On Behalf Of Chris
Dainton
Sent: 12 May 2009 11:01
To: [log in to unmask]
Subject: Re: New Soil Guideline Values - Arsenic, Nickel......
New values with old values in brackets
Arsenic:
Res: 32 (20)
Res w/o PU: No value (20)
Allot: 43 (20)
Com: 640 (500)
Nickel:
Res: 130 (50)
Res w/o PU: No value (75)
Allot: 230 (50)
Com: 1,800 (5,000)
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