Agriculture Reference
In-Depth Information
blast-averting sulfur, nurse, bring fire! / That I may fumigate
my walls.” It is likely that the Greeks had used sulfur since
prehistoric times, and that experience taught them how to
use it safely. Today synthetic pesticides are typically created
in a factory. New formulations are continually introduced,
ones humans do not have generations of experience using, so
controlled experiments are needed to determine what health
threat they may pose.
The United States requires all pesticides to be registered
with the EPA, and older pesticides are continually reviewed to
make sure they meet the newer safety requirements. When a
pesticide is registered, it can then be used, but only in settings
and at levels approved by the EPA. If the EPA makes wise deci-
sions about registering pesticides and determining approved
dosages, then little to no harm should come from pesticide use.
To determine whether a pesticide is safe the EPA first
requires the pesticide company to provide data regarding the
largest amount of pesticide residues one would expect to see
on the crops in the field (when pesticides are applied at their
highest dosage) and in processed food made from those crops.
The agency then seeks to determine if those residues are
harmful. This is where the tasters—laboratory animals—are
used. By exposing animals to different levels of the pesticides,
researchers can determine the threshold beyond which they
cause harm to the animals. This threshold can be stated in
terms of residues divided by the animal's weight, so that it can
be used to determine the appropriate threshold for humans.
In toxicology this threshold may be specified as a median
lethal dose, or LD 50 , which refers to the dose required to kill
half of the animals exposed in experiments. It is a standard-
ized dosage that allows us to compare the relative dangers
posed by different chemicals, and in doing so it sometimes
shows how safe many pesticides are. The herbicide glyphosate
used on almost all soybean acres has an LD 50 of 4,320 milli-
grams. This seems safer than table salt (LD 50  = 3,300 mg) and
much safer than caffeine (LD 50  = 192 mg). If you do not fear the
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