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There are pesticides and then there are pesticides. Most
anti-louse shampoos probably use pyrethrum or one of its
synthetic derivatives. Pyretrum is made from the dried and
ground-up flower heads of a certain species of chrysanthemum.
It is relatively non-toxic to warm blooded animals, but is deadly
to cold blooded ones such as insects, fish, and reptiles; it acts
like nerve gas to them. But it is bad news for people with
allergies; when the flowers are ground up, they are ground up
pollen and all. It has a number of synthetic derivitives and
analogs--allethrin, promethrin--that should avoid this problem.
On the other hand, organic phosphates (e.g. Malathion) and
chlorinated hydrocarbons (e.g. DDT) are much more toxic. Some
of these chemicals (e.g. Tetraethyl pyrophosphate) are so toxic
that a nearly microscopic droplet on your skin can kill you within
minutes. Progably the least toxic of the organic phosphates is
Malathion. The problem with Malathion is that while it is
relatively safe when used alone, there is a synergistic effect
when it is used in combination with other pesticides. Its
toxicity is magnified many times. (See Rachel Carson,
SILENT SPRING).
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alamosaurus
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