Re: Does dioxin degrade in the environment??

[Alan Watson <alanwatson@gn.apc.org>]

  Jon wrote:
  
  >That's FASCINATING! I understand, all too well,
  >that TCDD is the most stable of the compounds.
  >Are you saying that OCDD, etc actually degrade
  >to TCDD? That would be an INCREDIBLY POWERFUL
  >bit of information to oppose the use of 2,4 D which
  >I read (in another anecdote somewhere in the distant
  >past) is contaminated primarily with OCDD, which is
  >*only* 1/1000 as toxic as TCDD. But if OCDD 
  >stabilized to TCDD, then that is another matter
  >entirely!!!
   
  I agree.
  
  I don't know whether this happens in the environment or and what the 
  dynamics of the degredation reactions would be but it looks plausible and 
  I would think that it certainly merits further discussion.
  
  Another example that may strengten the argument is "Modelling study on 
  contribution of combustion source complex to PCDD/PCDF
  levels in urban air" by Yamamoto, T and Fukushimu, M.  Published in
  Chemosphere Vol 27 nos 1-3, pp295-300, 1993.  The authors fed emissions 
  data
  from Osaka MSW incinerators into an atmospheric dispersion model.  The
  PCDD/F concentrations measured in soil samples were compared with
  predictions from the air model and the results correlated.  Observations 
  in
  2,3,7,8-substituted congener pattern of soil samples collected from
  different sites indicated consistent composition and somewhat systematic
  changes from the combustion congener profile to the congener profile in 
  the
  soil samples.  The higher chlorinated congeners seemed to have degraded
  towards the more toxic, lower chlorinated congeners.
  
  The authors concluded that it was too difficult to model these effects.
  
  
  ........................................................
         _\\|//_                Alan Watson C.Eng                  
        (' O^O ')               Oakleigh                      
   ==|=ooO=(_)=Ooo=|==          Wernffrwd                            
     !             !            Gower                                 
     !   PUBLIC    !            Swansea   SA4 3TY                 
     !  INTEREST   !            UK                                    
     ! CONSULTANTS !            Tel: 01792 851599                   
     !             !            Fax: 01792 850056                     
     !             !   Check out:                           
     ^^^^^^^^^^^^^^^   http://www.gn.apc.org/pmhp/            
                       For UK issues and information                
  ........................................................