Weeds suck nutrients from the soil, thus fewer nutrients left for the crops that you wantInsects – the corn borer for example invades our cornNematodes destroy the roots of apple orchards treesOne of the first chemicals that was used wasSulfurSulfur can be mined (it occurs in nature in its elemental form)When you burn sulfur, it produces sulfur dioxide: SO2kills many insects and fungiOne of the first insecticides ever used – but has a chocking odorTobacco plant – produces nicotine
24The plant evolved to protect itself against insects Nicotine is a natural insecticide!!Synthetic pesticides(made in the laboratory):oCopper acetoarsenate– which can be made by combining arsenic trioxide and copperacetateCalled “Paris Green”, because it was used to rid the sewers of Paris (rats andmice)It was sold as a pigment and used in paintsWallpaper was dyed with Paris Green and some arsenic compounds wouldevaporate out of the paper… Rumor has is that Napoleon was poisoned in hisprison cell because of the wallpapersoDDT – very effective against fleas, all kinds of insects, mites and ants, anything thatcrawledDuring WW2, the Allied soldierswere spread with DDT, which kept them free oflice and insects that could transmit typhoid fever (so they were healthier thanthe Germans)The W.H.O estimates that ~25 million lives saved because of the use of DDTPaul Muller, the physicist who introduced DDT, received a Nobel Prize inmedicine in 1948The problem in DDT it was too good, farmers overused DDTIt was even sprayed on beaches!The first problem that was noted was that eggshells that were laid by birds broketoo frequently, so that there were fewer hatchingsDecline in the population of the eagle and the ospreyRachel Carson and her classic book “Silent Spring” introduced the idea thatpesticides were a double-edged swordShe used DDT as an example, and explained how it build up in the food chain, itisn’t biodegradable, it gets into the water, fish consume it, bigger fish eat thesmaller fish, birds eat the fish, etc.1969: banned in Canada1972: banned in the US2006: The W.H.O suggests DDT be used to control Malaria in AfricaIt will kill the mosquito that transmits MalariaSpraying a powdered version on the inside of homesHow dangerous was DDT?Rats exposed to traces of DDT develop fewer livertumors than unexposed ratsExposure to DDT causes the animal to generate some detoxicating enzymes thatwill then detoxicate other substances as well (that has never been shown inhuman)Berkeley Public Health Institute: Among women who were under 14 years ofage during heaviest DDT exposure (1945-1959) blood levels of DDT were foundto correlate with future breast cancer riskLong Island Study: No relationship between breast cancer and blood levels ofDDT, but blood samples were taken after cancer was diagnosed
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- Spring '11
- Silent Spring, Food coloring, Sucralose, E number, Food additive