STANFORD UNIVERSITY
      MEDICAL CENTER
   PALO ALTO, CALIFORNIA

DEPARTMENT OF GENETICS
?????o o ? ??????*

March 19, 1960

Dear Dr. hurli&er-

Thank you for the material.

  I have no information on mutagenicity of DDT.   I would caution
you on loose talk and misinterpretation, lil\e the enclosed, which
confuses selective effects (favoring better adapted genotypes) with
mutation-induction.

  In fact, our general methodology in this area is very bad. Before
long every compound is going to flunk the leucocyte/chromosome
breakage test, which may discredit the whole inquiry.  By the same
token we might have to inculpate coffee, and we would if we did not
have a better understanding now of alhe mechanism of action of caffeine
(an inhibitor of some enzymes of DNA repair) that rule out a simple   E
extrapolation from high dose&in laboratory experiments to low ones in   -
human exposure.                                             a
  A propos DDT, one of my deepest concerns would be its ecological     m
impact, i.e., the selection for more resistant species of marine
algae t)rnlpxanx which could have serious adverse effects long before  ;;\
we actually had to worry about the termination of photosynthesis.    )b
Finally, I would be disappointed at a ruling that peremptorily

forbade DDT. It ought to be licensed and regulated, perhaps even
taxed to balance the merits with the costf;.   I am afraid this kind
of blanket determination may set a very poor precedent for making
a flexible response)! to other social irritations where your and my
own preferences might be quite on the other side.  'ihe legal approach
to marijuana is a case in point.

PS: Is the whole subject of
DDT effects going to be reopened
by differential effects of the
o- and p- isomers?