animals give more prompt results, and after the two years it was evident that this miticide was
indeed a carcinogen. Even at that point, in 1957, the Food and D rug Adminis tration could not
instantly rescind the tolerance which allowed residues of a known carcinogen to contaminate
food cons umed by the public. Anothe r year was requi red for various legal procedures. Finally,
in December 19 58 the ze ro tolerance which the Commis s ioner had recommended in 1955
became effective. Thes e are by no means the only known carcinogens among pes ticides. In
laboratory tests on animal subjects, DDT has produced s us picious liver tumors. Scientis ts of the
Food and Drug Admi nis tration who reporte d the dis covery of thes e tu mo rs were u ncertain h ow
to classify them, but felt there was some ‘justification for considering them low grade hepatic
cell carcinomas.’ Dr. Hueper now gives DDT the definite rating of a ‘chemical carcinogen’.
Two he rbicides belonging to the carba mate group, IPC and CIPC, have been found to play a role
in producing s kin tumors in mice. Some of the tumors were malignant. These chemicals seem to
initiate the malignant change, which may then be completed by othe r chemicals of types
prevalent in the environme nt.
The weed-killer aminotriazole has caused thyroid cancer in test animals. This chemical was
mis us ed by a number of cranbe rry growe rs in 1959, producing res idues on s ome of the
marke ted be rries. In the controve rs y that followed s eizure of conta minated cranberries by the
Food and Drug Administration, the fact that the chemical actually is cancer producing was
widely challenged, even by many medical men. The scientific facts releas ed by the Food and
Drug Administration clearly indicate the carcinogenic nature of aminotriazole in laboratory rats.
When these animals were fed this chemical at the rate of 100 parts per million in the drinking
water (or one teas poonful of chemical in ten thous and teas poonf uls of water) they began to
develop thyroid tumors at the 68th week. Afte r two years , s uch tumors were pres ent in more
than half the rats examined. They we re diagnos ed as various types of benign and malignant
growths. The tumors also appeared at lower levels of feeding—in fact, a level that produced no
effect was not found. No one knows , of cours e, the level at which aminotriazole may be
carcinogenic for man, but as a professor of medicine at Harvard University, Dr. David Ruts tei n,
has pointed out, the level is just as likely to be to man’s disfavor as to his advantage.
As yet insufficient time has elapsed to reveal the full effect of the new chlorinated hydrocarbon
ins ecticides and of the mode rn herbicides. Mos t malignancies develop so slowly that they may
requi re a cons iderable s egment of the victim’s life to reach the stage of showing clinical
s ymptoms. In the early 1920s women who painte d luminous figures on watch dials swallowed
minute amounts of radium by touching the brus hes to thei r lips ; in s ome of thes e women bone
cancers developed after a lapse of 15 or more years. A period of 15 to 30 yea rs or even more
has been demons trated for s ome cancers caus ed by occupational expos ures to chemical
carcinogens.
In contras t to thes e indus trial expos ures to various carcinogens the firs t expos ures to DDT date
from about 1942 for military personnel and from about 1945 for civilians, and it was not until
the early fifties that a wide variety of pesticidal chemicals came into use. The full maturi ng of
whateve r s eeds of malignancy have been s own by thes e chemicals is yet to come.
There is , however, one pres ently known exception to the fact that a long period of latency is
common to mos t malignancies. This exception is leukemia. Survivors of Hiroshima began to
develop leukemia only three years after the atomic bombing, and the re is now reas on to
believe the latent period may be cons iderably s horter. Other types of cancer may in time be
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