October 18 Chlorinated Hydrocarbons

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• October 18 Chlorinated Hydrocarbons
• Chlorinated Hydrocarbons
• Co-exist as mixtures (congeners) in environment
• 3 categories of mixtures Dioxins, Furans, PCBs
  100s of individual chemicals
• All are toxic, persistent, bioaccumulative some
  worse than others (vary 10,000 fold)
• Public health threat rivals that of DDT in the
  60s
• In 90s, biomonitoring of levels of these
  chemicals in general US population showed levels
  at or near those known to produce adverse health
  effects (cancer reproductive toxicity
  neurotoxicity)

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• II. Dioxins
• Many individual ones varying in toxicity
• Most toxic is 2,3,7,8-tetrachlorodibenzo-p-dioxin
  (TCDD)
• Toxicity of other dioxins, furans, and PCBs are
  measured in relation to TCDD (often called
  dioxin)
• Not manufactured, but a by-product of other
  products
• Formed during waste incineration, backyard trash
  burning, chemical and pesticide manufacturing,
  pulp and paper bleaching, production of polyvinyl
  chloride (PVC) plastics

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• III. Exposure to Dioxins
• WHO TDI set at 1-4 pg/kg bw/day
• Picogram is 1 trillionth of a gram
• Average US adult intake is now 0.5-1 pg/kg/day
• In past, it was much higher and in danger zone
  decreased 50-75 1980-1996 (related to air
  quality laws)
• Industrial sources reduced by 80 between 1987
  and 1995 and expected to have fallen 90 since
  then due to EPA regulations
• Todays main new sources (57) backyard burn
  barrels agricultural burning, landfill fire

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• III. Amount of Exposure to Dioxins
• 95 of our exposure through foods
• Bioaccumulates so mostly meat, dairy, fish, eggs
• Significant bioaccumulation fish may have
  100,000x that of waters
• IV. Adverse health Effects
• Acute, High levels ? chloracne
• Chronic cancers in workers
• V. Best Example of Toxicity Viktor Yushenko
  story

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• PCBs Polychlorinated Biphenyls
• Unlike dioxins, these are commercially made
  contain 21-60 chlorine
• Exist as oily liquids, solids, vapors no smell
  or taste
• Used as coolants and lubricants in transformers,
  capacitors, and other electronic equipment
  because they dont burn easily and make good
  insulators
• Leading tradename - Aroclor
• Banned in 1977
• Before 1977, in flourescent lighting, capacitors,
  old microscope and hydraulic oils
• Now found in 1/3 of Superfund Sites and in
  general environment soils, waters ? fish and
  wild sport animals ? diet. Air from use of old
  fixtures or from burning ? inhalation
• Occupational risks for firefighters and those
  that work at incinerators