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Re: Does dioxin degrade in the environment??
At 09:16 AM 8/1/97 -0400,email@example.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
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