Dioxin body burden increases with age

["james lynch" <james_lynch@berea.edu>]

Hello,

    I am doing a little research on the topic of dioxin's so I can make a feeble 
attempt at assessing the risks of a proposed military incinerator at the Blue 
Grass Depot in Richmond, Ky, and I have a few questions.  I hope that this is 
the appropriate forum; I have been trying to find out the answers on my own 
(well, myself and my fellow researchers), but I can't seem to locate anything 
that addresses this issue;  so I hoped maybe real live people could help.  I 
apologize if this is not kosher.

    Anyway, we have been trying to calculate how much dioxin will be in our 
bodies given some exposure rate (such as .006 pg/kg/day deemed "safe" by the 
EPA) over time.  We assumed that this rate was the amount coming in, and what 
came out (dissipated or was passed or what we are not concerned with) was 
determined by the half-life of dioxin as reported in several studies (the EPA's 
figure was a half-life between 7 and 11 years).  But this leads to an 
exponential model, namely D(t)=R/k(1-exp(-kt)), where D(t) is the amount of 
dioxin in the adipose, R is the rate dioxin enters the body, and k is the half-
life constant of dioxin in adipose. 

    Now, there is something horribly wrong with this work.  First of all, my 
subject line.  By this logic and given the incredible rates of dioxin exposure 
of infants and teenagers, it just doesn't make sense that the body burden 
increases with age.  But also, the current body burdens (as we found in the 
Adipose Tissue survey --I can not recall the name of the organization--um, did 
it in 1982 and again in 1987) would require far higher rates of exposure than 
most figures I have seen (breast-fed infants yes, but no one else, it seems).  

    My question is simply, what's wrong?  Why does the EPA say .006?  Is the 
half-life not relevant here; if not, why not?  I've seen papers discuss it, but 
never have I seen them use it in their modelling.

    Oh well, I don't want to go on too much, especially if I'm asking questions 
that are not appropriate here.  If they are appropriate, naturally, I have 
plenty more.  So, be careful.  


                                    Oh, and thanks,

                                    James K. Lynch