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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
  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