There are s trong indications that fields clos er to our daily lives are being opened up. You may
now give y our dog a pill which, it is claimed, will rid him of fleas by making his blood poisonous
to them. The hazards dis covered in treating cattle would pres umably apply to the dog. As yet
no one s eems to have propos ed a human s ys temic that would make us lethal to a mosquito.
Perhaps this is the next s tep....
So far in this chapter we have been dis cuss ing the deadly chemicals that are being us ed in our
war against the insects. What of our s imultaneous war agains t the weeds? The desire for a
quick and easy method of killing unwanted plants has given rise to a large and growing array of
chemicals that are known as herbicides, or, less formally, as weed killers. The s tory of how
thes e chemicals are us ed and mis us ed will be told in Chapter 6; the ques tion that he re conce rns
us is whethe r the wee d killers are pois ons and whethe r their ris e is contributing to the
pois oning of the environment.
The legend that the herbicides are toxic only to plants and so pose no threat to animal life has
been widely dis s eminated, but unfortunately it is not true. The plant killers include a large
variety of chemicals that act on animal tissue as well as on vegetation. They vary greatly in their
action on the organism. Some are general poisons, some are powerful s timulants of
metabolism, causing a fatal rise in body temperature, some induce malignant tumors either
alone or in partnership with other chemicals, some strike at the genetic material of the race by
caus ing gene mutations. The herbicides , then, like the ins ecticides , include s ome very
dangerous chemicals, and their careless use in the belief that they are ‘s afe’ can have dis as trous
results. Des pite the compe tition of a cons tant s tream of ne w chemicals iss uing from the
laboratories, arsenic compounds are still liberally used, both as insecticides (as mentioned
above) and as weed killers, where they usually take the chemical form of s odium ars enite. The
his tory of their us e is not reass uring. As roads ide s prays , they have cos t many a farmer his cow
and killed uncounted numbe rs of wild creatures. As aquatic weed killers in lakes and res ervoirs
they have made public waters uns uitable for drinking or even for s wimming. As a spray applied
to potato fields to des troy the vines they have taken a toll of huma n and nonhuman life.
In England this latter practice developed about 1951 as a result of a shortage of sulfuric acid,
formerly us ed to burn off the potato vines. The Minis try of Agriculture cons idered it neces sary
to give warning of the hazard of going into the arsenic-s prayed fields , but the warning was not
unde rs tood by the cattle (nor, we mus t pres ume, by the wild animals and birds ) and reports of
cattle pois oned by the arsenic sprays came with monotonous regularity. When death came also
to a farme r’s wife thro ugh ars enic-contaminated water, one of the major English chemical
companies (in 1959) s topped production of arsenical sprays and called in supplies already in the
hands of dealers , and s hortly thereafte r the Minis try of Agriculture announced that becaus e of
high ris ks to people and cattle res trictions on the us e of ars enites would be imposed. In 1961,
the Australian government announced a similar ban. No such restrictions impede the us e of
thes e pois ons in the United States , however.
Some of the ‘dinitro’ compounds are als o us ed as herbicides. They are rated as among the mos t
dangerous materials of this type in us e in the United States. Dinitrophe nol is a s trong me tabolic
stimulant. For this reason it was at one time used as a reducing drug, but the ma rgin between
the s limming dos e and that require d to pois on or kill was s light—so slight that s everal patients
died and many s uffered permanent injury bef ore us e of the drug was finally halted. A related
chemical, pentachlorophenol, sometimes known as ‘penta’, is used as a weed killer as well as
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