New dioxin research

[slester@essential.org]

In the September 1995 issue of "Environmental Health Perspectives" 
(v.103, n.9), there are two good articles related to dioxin that we 
thought you all should know about.  The first is titled "Comparisons of 
Estimated Human Body Burdens of Dioxinlike Chemicals and TCDD Body 
Burdens in Experimentally Exposed Animals."  It was authored by Michael 
J. DeVito, Linda S. Birnbaum, William H. Farland, and Thomas A. 
Gasiewicz.  

ABSTRACT:

Humans are exposed to mixtures of polyhalogenated aromatic hydrocarbons, 
and the potential health effects of these exposures are uncertain.  A 
subset of this class of compounds produce similar spectra of toxicity in 
experimental animals as does 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 
and these chemicals have been classified as "dioxins."  IN this study, we 
compared the body burdens of dioxins that produce effects in experimental 
animals to body burdens associated with these effects in humans.  Human 
body burdens wee estimated from lipid-adjusted serum concentrations of 
dioxins, assuming dioxins are equally distributed in body fat and an 
adult has 22% body fat.  The toxic equivalency factor (TEF) method was 
used to calculate body burdens of dioxins in humans.  These calculations 
included dibenzo-p-dioxins, dibenzofurans, and polychlorinated 
biphenyls.  IN the general population, average background concentrations 
were estimated at 58 ng TCDD equivalents (TEQ)/kg body weight.  For 
effects that have been clearly associated with dioxins, such as chloracne 
and induction of CYP1A1, humans and animals respond at similar body 
burdens.  Induction of cancer in animals occurs at body burdens of 
944-137,000 ng TCDD/kg body weight, while noncancer effects in animals 
occur at body burdens of 10-12,500 ng/kg.  Available human data suggest 
that some individuals may respond to dioxin exposures with cancer and 
noncancer effects at body burdens within one to two orders of magnitude of 
those in the general populations.  


The second article is titled "Focus:  Assault on the Male."  This article 
deals with the effects that exposure to environmental estrogens can have 
on the male reproductive and endocrine systems.  Some of these effects 
include prostate and testicular cancers.  

Both these articles would be good to check out.  We hope you find them 
helpful.  

Michael Drescher
Citizens Clearinghouse for Hazardous Waste
e-mail:  slester@essential.org