Re: dioxins cigarette smoking/EPA's draft inventory

[ttweed@wildrockies.org (Tony Tweedale)]

>At a recent seminar on dioxins a Public Health Official, in trying to avert
>attention from the high dioxin emissions from the local sinter plant,
>stated that cigarette smoking also produced dioxins. It was claimed that 20
>cigarettes could expose a person with 4.3 pg/kg/day.
>How correct is this and is there a scientific paper to back it up ?
>Thanks for your help and I apologize if this subject has been discussed before.
>
>Yoke Berry
>Wollongong
>Australia
---

EPA/ORD's '4/98 External Review Draft (sensitively printed on Unity DP's
unbleached paper) of "The Inventory of Sources of Dioxins in the U.S.' is
relatively thorough, including estimates of releases in products; and it's
discussion is direct, simple & thorough.  For example, it ranks and
discusses the estimates by confidence of accuracy, so while it is very
thorough in discussing and summarizing available source info for many
categories, it refrains from including many important ones in the actual
draft emissions inventory.  E.g:  backyard trash burning & l. fill fires (1
kg/yr, high uncertainty estimate) (TEq basis, incl coplanar PCBs, to be
consistent w/ their political hostage, the draft dioxin risk
(re)assessment).  Source emissions are estimated for '87 and '95.  It does
make the seemingly valid point that large, (combustion, presumably)
emissions sources may be quite far from the nation's food supply (ie fields
turned into feed for the animals you eat), so it cannot be assumed the
largest sources are the largest contributors to human body burdens.

It's outrageous they refuse to estimate EDC/VC dioxin releases, given that
there is enoough data (thanks in part to GPeace) now to at least give a
"highly uncertain" estimate.  Given that EPA has requested this type of
chemical data from industries hundreds of times over the years, I have
little doubt it's political.  Bldg fires, PCB combustion, petroleum
catalyst regeneration (a huge source, as I understand it), and scrap wire
regenration (burning off PVC coated copper wire--Cu is the ideal catalyst
for dioxin formation), PCP treated wood emissions (though PCP manufacture
is listed as far and away (89.9%) the largest source of dioxins (TEq basis)
in the USA, the releases from the wood it's used to treat (and intermediary
steps) aren't estimated (tho obviously exposure isn't near as great as
combustion sources)), and finally, reservoir sources--all these and some
others too, EPA begs-off with  "insufficient data to make an estimate".
Yet when thy do put an estimate in the inventory, the confidence can be as
low as a 10-fold spread in the number given.

Anyway, whether a source is in the draft inventory or not with an estimate,
the data summarized for all sources tends to be quite thorough, w/ useful
graphs & summary tables.  So, hopefully by the time it's finalized, a lot
more  of these critical estimates will be in place.  Note that EPA has an
Emissions Inventory Improvement Program (EIIP, in which it recognizes that
emission factors (concentrations) and inventories (mass amnts) are
generally always biased low--due to industry supplied data, data taken
during ideal stack test conditions, etc. etc.)  This is a massive problem
that makes something of a joke of everything EPA does in air pollution, as
EI & EF are used in almost every rule and permit in the country.  Of
course, dioxin emisison inventory data is based on an even wider range of
data quality...

So, for ciggies, they use several studies, and overall emissions of
0.25-2.5g (median 0.81g)/yr are averaged from 2 models, the low one
assuming no dioxins are formed during combustion (based on a large analysis
of dioxin content unburned).  During a drag, T's go from 900d.C to
200-400d.C 2 mm past the char line--this is an ideal dioxin formation T
drop, but EPA doesn't say that.  Confidence is high for the amnts of
tobacky burned, but low for the emission factor.  Nonetheless, typically, a
good deal of EF data is summarized.  EF's for burned ciggies had similar
congener profiles, but varied > 1 order magnitude, 0.09 - 0.9
pg/cigarrette.  In the large, unburned study, 109 -1,136 pg/*pack*, w/ the
low # coming from one Chinese brand (possibly unbleached paper?).  As
apparantly the congener profile in this & in one other small uburned study
is similar to the profiles when burned, EPA believes it valid to average
both models together (as above) for its inventory estimate.  Also given the
moisture that collects behind the char line, and the large # of compounds
known to be moved by a water distilation process from the tobacco into the
smoke in this unburned area, EPA again believes its plausible to assume
some of the inhaled dioxins are from unburned tobbacky.  But presumably
there's a lot of chlorine in the bleached paper not subject to this
distilation into the smoke stream, that instead is burned, liberated, and
converted into dioxins when the T drops (as they always are formed during
combustion).

Tony Tweedale

Causality is a concept not subject to empirical demonstration. -David Hume
(1711-'76)

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