Re: DIOXIN-L digest 547

[ttweed@wildrockies.org (Tony Tweedale)]

  i haven't checked lately, but the last time i looked at some of the
  literature 3-4 years ago, no one knew enough to declare any trends or
  general rules.  it also contradicts your statement about the env. stability
  of higher cl congeners.
  
  are you sure peterson wasn't refering to teq's?  that would be normal, make
  more sense.  if so it would invalidate it as a proof for you.
  
  >Subject: Re: Does dioxin toxicity increase in the environment??
  >Message-ID: <970802223514_-322649408@emout08.mail.aol.com>
  >
  >Most of the things I''ve seen recently seem to show that the higher
  >chlorinated materials are both more stable and less reactive (those are two
  >different things) and also are less volatile.
  >
  >Destruction reactions are mostly gas phase rather than sorbed on solids.
  > What this means is vvolatilization as well as photolysis or hydroxlation of
  >the octa are the rate determining steps: all others are faster, and there
  >would not tend to be an increase in TEQ due to buildup of lower chlorinated
  >congeners.
  >
  >This squares well with the difference seen between the fingerprint of sources
  >of emission (generally more furans and higher in penta) vs. environmental
  >samples (generally higher chlorinated and dioxins).
  >
  >Bill Carroll
  >Chlorine Chemistry Council
  >
  >------------------------------
  >
  >Topic No. 4
  >
  >Date: Sat, 2 Aug 1997 22:43:53 -0400 (EDT)
  >From: DrBillC@aol.com
  >To: cwac@execpc.com, dioxin-l@essential.org
  >Subject: Re: Does dioxin toxicity increase in the environment??
  >Message-ID: <970802224352_1081529909@emout07.mail.aol.com>
  >
  >One other note on the buildup of TEQ.
  >
  >Dick Petersen at Wisconsin notes that the return of trout is due to reduction
  >in TCDD concentrations.  He says the critical level in fry for development is
  >30 ppt.  Levels were as high as 100 years ago, and now are at about 5.
  >
  >He noted in a recent interview that levels peaked about 1970 "and have been
  >dropping" ever since.  This would not be consistent with degradation of
  >higher congeners to TCDD.
  >
  >Bill Carroll
  >Chlorine Chemistry Council