Memo from | To: miss Mary D. Wills
JOSHUA LEDED BERG MAY 17 1971

Human toxicity of defoliants

~ am somewhat mystified why Mr. Conrad lumps me

with Meselson and Sidel, as IT have taken 4 rather
different position on defoliants, and in any case
do not pretend to have authoritative information
about them. It ts clear that some batches of
2,4,5-T were contamhnated with dioxins, and that
the Latter played an important part in fetal damage
in the experiments conducted by the Bionetics res.
labs. Later experiments have given confliciting
results on the question of damage from 1) chemical
ly purified samples of 945-T, and 2) samples typi-
cal of general commercial output. 1 do not know
what is being used in Vietnam; tn the Light of all
these uncertainties, it would certainly be prudent
(as eth military authorities have done) to Limit
the use of these chemicals in any circumstances
where they maz might enter the food chain.

On the whole, 1 would consider these sideseffects
to be relatively unimportant compared to the direct
effects of f irepower-

Dr. Meselson has been much more deeply involved in
the study of defoliants, and I suggest that you ‘
write him directly at the Dept. of Biology,

Harvard University.

Sincerely,

cc: Mr. Conrad

PROFESSOR JOSHUA LEDERBERG
Department of Genetics
Schoo! of Medicine

Stanford University
Stanford, California 94305