Question re dioxin levels

msadkins04_at_yahoo.com
Date: 12/28/04 

Date: 28 Dec 2004 13:18:26 -0800

An Associated Press article by Paul Recer, appearing in the
Sunday, December 26, 2004 edition of the Arizona Republic,
compared the dioxin level measured (in one test) in Viktor
Yushchenko, with that of Vietnam War era veterans exposed to
Agent Orange.

The article stated "it is unlikely if many, if any, Americans
absorbed the dose Yushchenko ingested". It then went on to
descibe Yushchenko's dioxin level as "100,000 units per gram of
blood fat"; it then gave estimates from "studies" conducted years
after the war's end, of dioxin levels in veterans ranging from
5 parts per trillion to 20 parts per billion.

Well, 100,000 to 1 certainly sounds bigger than 5 out of
a trillion or 20 out of a billion: but it is obvious to me
that these measurements do not use the same measurement
scale and that they are therefore incommensurate. The
comparison would be quite misleading to those who lacked the
scientific/mathematical literacy necessary to realize that
these figures represent two different measuring scales. At
the same time, it can be expected that most readers lack the
technical medical background necessary to convert these figures
into a single commensurable measurement scale, permitting a
meaningful comparison between them. I myself lack this
specialized knowledge.

How many parts per X does "100,000 units per gram of blood fat"
represent? Alternately, how many units per gram of blood fat
does 20 parts per billion represent?

Also, are these studies merely models using assumptions (without
actual measurements of dioxin levels) about the exposure of
"the typical" Vietnam veteran under specific conditions? Do
these studies rule out the possibility of much higher exposures
among vets than these studies suggest, given conditions that
may or may not have been exceptional? How does one measure
the "likelihood" of such exposures, and to what concept of
probability does this conform?

Obviously studies conducted years after a war cannot measure
contemporary levels, so to the extent that these studies
incorporated actual measurements at all, these would have been
some sort of residual levels (in organ tissues?) and then used
more assumptions to retroactively model the levels years earlier.
Or perhaps it merely examined existing unrepaired organ or other
tissue damage and made similar assumptions and retroactive
modeling. How reliable are such indirect methods (whatever those
might be), when recent newspaper reports gave widely varying
contemporary measurements of Yushchenko's dioxin level using
different tests with varying methodologies, and suggested that
even with such direct and recent measurements, obtaining an
accurate measurement of Yushchenko's dioxin level required the
work of a rare specialist lab to verify the quantification?
.
Mark Adkins
msadkins04@yahoo.com