Comments:
Effects of Chlorpyrifos
I have been working on this problem of how it is that pesticides cause chronic toxicity effect for several years now. My conclusion is that
chronic toxicity is not related to whatever it was that made a chemical an insecticide or herbicide in the first place. If this were the case, PCBs would have no long term toxic effects.
I have most of the data I need now and hope to get it organized and on the web shortly. Thanks for putting this out.
Bill Plapp
I've been saying this since I worked on the birth defects cases....
The critical portion of chlorpyrifos is NOT the OPO4... it is the tri-chlorinated part!!!!!!
Thanks for all your hard work.
Janette Sherman, MD
Hi Steve:
As long as Dow can keep the world looking for cholinergic
effects, there will be no progress as to why Dursban (chlorpyrifos) is such a
health hazard.
Rather than looking at ChE effects, researchers should
note the similarity of chlorpyrifos to TCDD, 2,4-D and 2,4,5-T.
All of these contain phenyl or pyridyl groupings containing 2 or 3
chlorines. In the case of TCDD,
it is well established (A. Brouwer
et al. from the Netherlands) that TCDD binds to transthyretin, the
carrier protein that moves thyroid hormones and vitamin A from storage sites
to the liver, where they are active. If
the protein is poisoned by reacting with dioxin (PCBs do the same thing) there
will be a shortage of retinoic acid in the liver.
This shortage means protein synthesis will be decreased.
This means a shortage of enzymes to degrade the chemicals and a
shortage of antibodies for antigens. No
wonder TCDD and the phenoxyacetic acid herbicides are carcinogens.
I am no longer in research but it seems obvious to me
that chlorpyrifos, like its Dow-derived relatives, will react with
transthyretin. It is also likely
that chlorpyrifos will poison the esterases that activate retinol, the vitamin
precursor of retinoic acid, by inhibiting the process of turning storage
retinyl esters to retinol.
These are the questions that need asking.
Working with PCBs and TCDD, the chemistry of 30 years ago, is simply
not pertinent to the problems we face today.
What is the critical need today is the measurement of the
interference of pesticides with the action of retinoic acid via either
transthyretin binding or inhibition of the esterases. Strange, isn't it, that no work in this area is never done in
the U.S.?
Bill Plapp