Re: Does dioxin degrade in the environment??

[asagady@sojourn.com]

  At 09:16 AM 8/1/97 -0400,cwac@execpc.com wrote:
  >Several years ago, Wisconsin research with the landspreading of 
  >dioxin contaminated paper mill sludges was used 
  >to claim that dioxins have a 10 year half life.
  >
  
  If they use landfarming technique with the big wheels
  subsurface injector, you would expect minimal photodegradation
  of any chlorinated dibenzo dioxin/furan contaminants present.
  
  The biggest problem with both aqueous and solid wastes from
  bleached kraft mill bleaching plants is that  they are contaminated
  with potentially thousands of chemical compounds, including
  many chlorinated organics for which there is absolutely no
  toxicology data.   Some of these materials are also volatile
  organic compounds and the mere spreading of pulp mill 
  sludge is likely to be an uncontrolled emission source of 
  these as well. 
  
  >Unfortunately, when I quizzed the lead researcher 
  >(Dr. Jack Sullivan, Wisconsin Dept. of Natural 
  >Resources) about this, he admitted that although 
  >half the dioxins disappeared in 10 years, they 
  >didn't know where they went or if they degraded.
  >
  >This makes the "half-life" claim terribly 
  >misleading.  The term "half-life" should only be 
  >used to describe actual degradation.
  >
  
  In order to really figure this out, you would have to 
  radio-label some of the dioxins to see if some of
  the carbons or chlorines remained in the sample
  in another form.  You'd probably also want to 
  track, collect and capture soil gases and water
  leachates....   considerably tougher and more
  expensive research than just measuring PCDD/F
  contents in the soil on an annual schedule.
  
  The other problem with soil tests is that it is 
  difficult to know whether you have an appropriate
  representative sample when any degradation 
  or transport mechanism may be depth dependent or 
  dependent on the actions of biological 
  mechanisms which are depth dependent.
  
  I agree with you on the concerns about land 
  spreading kraft mill waste.  EPA acted 
  precipitously to allow this without having all 
  of the facts.   Dedicated landfilling and not
  agricultural land spreading is how this waste
  should be handled.
  
  When bleach plant wastes are mixed with 
  fly ash from coal fired boilers at kraft mills, you 
  also have the issue of thallium and arsenic
  contamination of such sludges.
  
  
  >If dioxins break down, how long do the breakdown 
  >products last? --- How toxic are they? --- And 
  >where do they go?   
  >
  >If photodegradation is a 
  >solution, why would air pollution sources of 
  >dioxin be such a concern? 
  
  I didn't say photodegradation is a "solution;"  I was 
  merely pointing out that chlorinated dioxins/furans
  can degrade in the environment so that it is 
  plausible that such compounds emitted long ago
  could degrade or migrate, so if they are not found
  in 1880 sediments that does not mean that they
  were not emitted by coal burning and metal processing
  of that time.
  
  The reason why dioxin air pollution is such a concern
  is that emissions of it are fully capable of elevating 
  health risks from inhalation and non-inhalation 
  exposures, even if some of it degrades or
  "photodechlorinates" prior to entering some 
  living thing.
  
  
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