Re: DIOXIN-L digest 164

[cmcr@ism.net (Cold Mountain, Cold Rivers)]

responding to ferdinand w/out taking up a lot of kilobytes, and hoping he
(mark too) will slim down too.  we _all_ are busy, i know, and will benefit
from concise but strong posts.

in this last regard, ferdinand especially needs to cite summarized peer
reviewed data!  i'm not going to reply to his constant but prposterous
assertion that pvc is a trivial source of dioxins, other than that i don't
recall any peer reveiwed references he made (there may have been, as i
wasn't actively checking).  and for all the data you do post, try to make
your point with less of it!

regarding your dioxin formation in incinerators, i found it useful.
charlie cray cited a _chemosphere_ refutation, that there is a direct
relationship between dioxin formation & pvc input.

thomas & spiro 'an estim. of dioxin emissions in the u.s.' _tox. & env.
chemistry_ 50:1-37 (jan '95) show, based on review of studies, a clear (and
greater than 1:1) relationship of dioxin formation:chlorine burning feed
content (fig. 1): "In hospital waste, a large fraction...PVC...while in
municipal waste a significant fraction may be in the form of sodium
chloride...The figure indicates that, by & large, dioxin emissions are
roughly independant of the original form of the chlorine...According to the
current understanding..., HCl is the chlorine source for dioxin formation
in catalyzed rx on fly ash...HCl is formed during combustion as part of the
breakdown process of Cl containing molecules.  Thus the amt. of HCl formed
might not depend strongly on the type of chlorine compound, although the
conversion of chloride salts to HCl is uncertain."  [because chloride ion
is so stable? --this would be a big q. in the only known natural source of
dioxins, biomass fires.  also, several studies show you can form dioxins
from aromatic precursors and from indiv. C atoms, in the lab anyway.].

this article is a thorough investigation into dioxin sources, and has
detailed emission data, by source.  it concludes there is no source gap (ie
in previous studies there's ~10x more dioxin in the general environment
than known sources have been estimated to have emmited).  their estim.
total annual dioxin emissions--400kg--are in rough agreement with measured
environmtl. concentrations.  ie, they estimate (w/ cites & discussion) much
more emissions.  and they estim. anthropogenic emmissions as 10x > than
natural.  all in all, it's another data point on dioxins sources.


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