I had an embarrassing moment today when I forgot what DDT stood for, and when I finally thought I'd gotten it, I was proved wrong by a student of English literature (for crying out loud). I agree that literature students also went to school and learnt these things in the chemistry classes, but an engineer is supposed to know better; in fact, a prospective science journalist ought to know better! Consequently, I'm imposing upon myself a punishment: a sufficient explanation of the synthesis, applications and mechanisms of action of DDT.
DDT stands for dichlorodiphenyltrichloroethane - yes, that's one word. The International Union of Physical and Analytic Chemists doesn't care if it takes even the accomplished science student a couple reads to get that right, but as long as it's a perfect representation of the molecule, it makes the cut. Anyway, it was first synthesized in 1874 by Othmar Zeidler, an Austrian chemist who reputedly completed his doctoral studies at the age of 14. The compound's pesticidal properties were discovered in 1939 by Swiss chemist Paul Herman Muller, and it was subsequently deployed on a large scale in the Second World War to quell malaria and typhus among the troops. After the war ended, its application as an insecticide gained popularity. Soon, it's production and use in agricultural establishments went through the roof.
I'm an amateur toxicologist, and one of the things I find fascinating about DDT is its simple mechanism of action in insects: it opens the sodium ion channels in the neurons. What happens is, in simple words, the voltage across the neuron's cell membrane rapidly rises and falls over a short interval, causing sodium ions to move from inside the cell to outside it and potassium ions from outside the cell to inside it. This gives rise to a charge gradient that is used in intracellular communication: signals are spontaneously fired to muscles commanding them to contract and dilate repeatedly, resulting in a spasm and eventual death.
DDT's mechanism of action in humans is more complex because it affects the human endocrine system. DDT is xenoestrogenic, which means it is similar enough to estrogen by way of its behavior and properties to trigger hormonal reactions. Its effects are on semen quality, menstruation, lactation periods and chances of getting pregnant. Dichlorodiphenyldichloroethane, or DDE, which is a DDT metabolite, behaves as an antiandrogen in the human body. They block the production of androgens, compete with them for receptor sites or block such sites entirely, resulting in the biological effects of androgens prevented from being expressed on living tissue. Since antiandrogens are involved in pre- and neo-natal development, reduced cognitive skills in a child could well be attributed to the possible (and accidental) ingestion of DDT by the mother.
I don't think I'll forget what DDT stands for ever again, or, for that matter, what DDE stands for, too. Such embarrassment.
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