Herbicides and PCB’s

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

Herbicides

• Most important other herbicide is glyphosphate (Roundup)– Not a selective herbicide

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

PCB’s in a Great Lakes area

TEQ = Toxicity equivalency

Chloracne from organochlorine compounds

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.

H24 – C10

• 31 - 34, 37, 38, 41, 44, 46, 74, 76, 89, 91 - 93