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RE: Background Dioxin Levels?
Are Dennis's values in TEQ or not? I assume not.
Lets see if this message gets through (On August 17, I tried to send some
spreadsheets of dioxins in UK cowsmilk from near industrial sources. That
message was rejected by the dioxin list server as being too big - if anyone
is still interested in cowsmilk sampling, please let me know and I'll make
time to split it down into smaller chunks).
I attach Excel spreadsheet data from the 1995 UK report by H.M. Inspectorate
of Pollution (HMIP) on dioxin in UK soils. [1]
Our computer is virus-checked every time it is powered on, so the attached
file should be safe to use.
This small subset of samples from survey of UK soil samples gives mean TEQ
values
Urban locations (Mean of 5 samples) = total I-TEQ 28.37 ng/kg (=ppt)
Rural locations (Mean of 11 samples) = total I-TEQ 5.17 ng/kg (=ppt)
The TEQ value for individual congeners are given in the spreadsheet.
N.B. Alan Watson says the data in that report is not very representative of
background dioxin levels in UK soil. He says that when he has time, he will
find and send out some better data.
If you cannot read the spreadsheets and want the data instream, let me know.
As you see, this is much higher than the 2 ppt under discussion, but it is
total TEQ per sample. This report analyses most of the samples by total
tetra- to octa- PCDDs and PCDFs, reanalysing relatively few samples into TEQ
values. They gave a statistical summary of the full urban data set of 28
samples, which showed
full urban data set of 28 samples Report [1]
mean ppt median ppt
TCDD 70 60
PeCDD 80 70
HxCDD 170 180
HpCDD 640 280
OCDD 5500 740
They didn't give a statistical summary of the rural samples, which is a pity
as they would better represent "background" presumably.
It is interesting that in HMIP's earlier report [3] they give a summary for
a data set of 66 samples from a 50km grid across the UK (reduced from 78
samples by ignoring samples with value for any congener outside 2.5 std
deviations of the mean). This would be more like background:
Reduced data set of 66 UK soil samples (concentrations in ng/kg) Report
[3] 1989
mean ppt median ppt
TCDD 9.4 6.0
2,3,7,8-TCDD <0.5 <0.5
PeCDD 6.6 4.6
1,2,3,7,8-PeCDD <0.5 <0.5
HxCDD 38 31
HpCDD 66 55
OCDD 190 140
I wonder if Dennis is quoting median values, rather than mean values, as the
median values above match the means he quotes, from work I suspect is from
the same co-author in the same year of 1989. I personally never got a grip
of the difference between mean and median, (lies, damn lies and statistics
if you ask me), but there does seem to be a difference in practise, as above.
The original 2ppt figure (quoted by Rebecca's FDA person) = the same amount
as was estimated by a Dutch government committee (in 1996) to be the average
dioxin intake of the Dutch population [2], so I wonder if Rebecca's FDA
person was really talking about background level in food, after all.
The Dutch report said (p14) "Most adults in the Netherlands are exposed to
approximately 2 picogrammes of toxic equivalents of dioxin-like substances
per kilogramme of bodyweight per day." This committee derived, from animal
studies, a health-based exposure limit of 1 picogramme TEQ/kg
bodyweight/day, which they recommended instead of the WHO limit of 10 pg
TEQ/kg bw/day. As the Dutch population generally is exposed to twice their
recommended safe level, the committee concluded that the best way to limit
adults and babies intake to a safe level would be to reduce the exposure of
the whole population. I do not know whether the Dutch government has
accepted these recommendations.
[1] "Determination of polychlorinated biphenols, polychlorinated
dibenzo-p-dioxins and polychlorinated dibenzofurans in UK soils. 2nd
Technical Report" by E.A.Cox & C.S.Creaser. Published by the then UK
regulators, H.M. Inspectorate of Pollution, December 1995. I ASSUME that
the report is available from the UK Environment Agency, Rio House, Waterside
Drive, Aztec West, Almondsbury, Bristol, BS12 4UD, England, since HMIP
merged to become part of this Agency.
[2] "Dioxins. Polychlorinated dibenzo-p-dioxins, dibenzofurans and
dioxin-like polychlorinated biphenols" Health Council of the Netherlands:
Committee on Risk Evaluation of Substances/Dioxins. Rijswijk: Health
Council of the Netherlands, 1996; Publication no. 1996/10E
[3] "Determination of polychlorinated biphenols, polychlorinated
dibenzo-p-dioxins and polychlorinated dibenzofurans in UK soils." H.M.
Inspectorate of Pollution, 1989.
Viv Mountford
At 12:16 26/08/97 -0400, Catalano, Dennis wrote:
>This 2 -3 ppt range is a bit low actually from some references I have
>seen. A study of soils in the UK had mean values of background of 6ppt
>for TCDD up to 143ppt for OCDD. The furans ranged from 16ppt for TCDF
>to 32 ppt for HxCDF. This data can be found in:
>
>Survey of Background Levels of PCDDs & PCDFs in UK Soils, Chemosphere,
>Vol 18 Nos 1-6 pp 767-776 1989.
>
>Some papers I have read find similar levels in the US. I am sorry, but
>I do not have references to those at my fingertips.
>
>Dennis Catalano
> ----------
From: Rebecca Leighton Katers
To: Multiple recipients of list
Subject: Background Dioxin Levels?
Date: Tuesday, August 26, 1997 8:11AM
I was just told by an FDA policy person that
recent information shows that dioxin background
levels range from 2 to 3 ppt.
This seemed awfully high to me, so I questioned
him and asked if he meant background
in the food supply or natural background in the
soil --- and he said natural background in soil.
He said that the 1 ppt limit for the chicken
recall and fish farms was simply their limit of detection,
not a regulatory number.
Can anyone recommend key documents which show natural
background levels are lower?
Rebecca Leighton Katers
Clean Water Action Council of N.E. Wisconsin
2220 Deckner Avenue
Green Bay, WI 54302
Phone: 414-468-4243
Fax: 414-468-1234
E-mail: cwac@execpc.com
SOILSMP5.XLS