Herbicides and PCB’s. Herbicides Largest sales of any pesticide in US - $4bill/yr Most useful are...
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Transcript of Herbicides and PCB’s. Herbicides Largest sales of any pesticide in US - $4bill/yr Most useful are...
Herbicides• Largest sales of any pesticide in US -
$4bill/yr
• Most useful are selective ones– Phenoxy herbicides kill broadleaf plants
• 2,4-D kills broadleaf weeds but not grains and grasses
• 2,4,5-T kills broadleaf brush – now banned since middle 80’s in US
– Because there are trace amounts of dioxin in it– Agent orange is 2,4-D plus 2,4,5-T plus dioxin
• Di or Tri chloro phenoxylacetic acid
PCDD’s
• General family of chlorinated compounds that includes dioxin or 2,3,7,8-TCDD
• Very stable in the environment
• Toxic to animals in low concentrations, but may not be toxic to humans at all.
• Found all over the world in low concentrations
PCB’s
• Also chlorinated organic compounds that are very stable.
• Spread out everywhere– Even found in polar regions and in bottom of
the ocean
• Under heat, produce dioxin and PCDF’s (polychlorinated furans)– PCDF’s are more toxic to animals and we
think humans
Environmental Estrogens
• Estrogen-like compounds in the environment– Many man-made but some natural
• DDT, PCB’s and dioxins• Phytoestrogens in soy, wheat, apples, cherries,
etc.– May protect against some kind of cancers
– Interfere with the normal work of estrogen– May only be a problem at high concentrations
Tiny Concentrations
• Just because we can detect them, doesn’t mean that they are harmful
• Overall, humans are living longer, more productive lives
• We just like to scare ourselves.