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Re: Does dioxin degrade in the environment??
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- Subject: Re: Does dioxin degrade in the environment??
- From: "Rebecca Leighton Katers" <email@example.com>
- Date: Fri, 1 Aug 1997 08:16:29 +0000
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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.
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.
Jack admitted the dioxins could have simply moved
For example, the dioxins could have percolated
deeper in the soil or moved off-site with wind
and water erosion of the soil.
The dioxins were certainly moved off-site by
earthworms, birds or other wildlife (the study
showed that robins and other wildlife were
picking up dioxins from the soil organisms.)
The dioxins could also be volatilizing away by
air to settle down and contaminate some other
site downwind. (The Mass Balance Study of PCB
movement in the Fox River and Green Bay showed
that over 3,500 pounds of PCBs volatilize off the
surface of the river and bay each year.)
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? Why would dioxin
deposition on the soil surface or plants be a
concern. Isn't the air exposed to sunlight?
Date: Thu, 31 Jul 1997 22:23:14 -0400 (EDT)
To: Multiple recipients of list <firstname.lastname@example.org>
Subject: Does dioxin degrade in the environment??
At 07:28 PM 7/31/97 -0400, email@example.com wrote:
>There has been some discussion here about "natural"
>dioxin formation from the burning of coal and oil.
>There is a great deal of evidence that the burning of
>does *not* produce any significant amounts of dioxin.
>of older sediment have essentially ruled out the
>of dioxin. There is essentially no dioxin in sediment
>previous to 1940 (Czuczwa, 1984, 1985, 1986).
The above assumes to some extent that chlorinated dibenzo-dioxins will
never degrade in the environment.
However, according to the articles below, that may
not be necessarily the case. This guy discusses
a half-life of dioxins in soils at Seveso of 9.5 years, although
photodegradation of chlorinated dioxins/furans would
be unlikely to be a factor for buried sediments not
exposed to light (or contained in someones fat cells)..
As near as I can tell from other articles I've read,
PCBs are more stable and less susceptible to
degradation than chlorinated dibenzo-dioxins. That is
why PCBs have been found to be recycling between
atmosphere/water interfaces in the Great Lakes.
In addition, I've heard
about research at Michigan State University that
is examining the ability of naturally occurring
white rot fungi to dechlorinate
On the issue of dioxin formation from the burning of
coal, it is well known that such compounds can be formed
in cement kilns that do not burn hazardous waste. In fact,
non-waste burning cement kilns are in the list of EPA's
source catagories ranking dioxin emitters as I recall.
Dioxins that form in such situations arise from the action
of hydrogen chloride produced when inorganic chlorine
in coal is burned, producing hydrogen chloride. Hydrogen
chloride in turn reacts with ordinary straight chain hydrocarbons
commonly found in limestone or shale under the influence
metallic catalysts to form chlorobenzenes and chlorinated
phenols. These reactions occur downstream from the main
The chlorobenzenes and chlorophenols in turn are available to participate in
more catalyzed reactions to form chlorinated dibenzo-dioxins/
Ecotoxicol Environ Saf 1989 Oct;18(2):149-164
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) persistence in the Seveso
(Milan, Italy) soil.
Cerlesi S, Di Domenico A, Ratti S
Department of Nuclear and Theoretical Physics, University of Pavia, Italy.
Preliminary results of a new study on TCDD environmental
persistence at Seveso (Milan, Italy) are presented. For this study,
the most contaminated territory, Zone A, was divided into areas
to fractionate the available TCDD levels in soil into data sets
with reduced value spreads. In addition, various time subsets
were defined for each area. Selected data were fitted with the
exponential model y = y0.e-k.1. It was estimated that at least
1.2 kg TCDD was present in Zone A shortly after the accident.
On average, a considerable portion (23%) of this amount lay
on vegetation; TCDD which was not photodegraded or
volatilized before the heavy rains of fall 1976, was later washed
off and transferred to ground by water action. From this study,
mean analytical underestimations affecting January 1977 and
March 1978 contamination map data were on the order of 30 and
24%. All the above figures are considered optimistic. A few
years after the accident, mean TCDD half-life in soil appeared to
be 9.1y (t1/2-95% CLs, 6.2-17y).
Science 1977 Mar 25;195(4284):1337-1338
Environmental degradation of 2,3,7,8-tetrachlorodibenzo-p-dioxin
Crosby DG, Wong AS
Herbicide formulations containing known amounts of
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and exposed to natural
sunlight on leaves, soil, or glass plates lost most or all of the
TCDD during a single day, due principally to photochemical
dechlorination. Despite the known persistence of pure TCDD,
it is not stable as a contaminant in thin herbicide films exposed to
Abstracts with a considerable amount of
environmental content like these can be found on Pub Med....
The price is right.... Free searching!!!
Alex J. Sagady & Associates Email: firstname.lastname@example.org
Environmental Consulting and Database Systems
PO Box 39 East Lansing, MI 48826-0039
(517) 332-6971 (voice); (517) 332-8987 (fax)
Rebecca Leighton Katers
Clean Water Action Council of N.E. Wisconsin
2220 Deckner Avenue
Green Bay, WI 54302