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  1. 1. PolychlorinatedBiphenylsAditya G
  2. 2. Chemical Composition Name: Polychlorinated Biphenyls (PCB) General formula: C12H10-xClx, where x is an integer from 1 to 9
  3. 3. Chemical Reactivity Degraded by  Hydroxyl radicals  Photolysis  Bacteria and Eukaryotes  Reductive dechlorination – releases chloride ions  Oxidized by dioxygenase
  4. 4. Physical Characteristics Odorless, tasteless, clear to pale-yellow viscous liquid Low water solubilities  0.0027-0.42 ng/L High solubility in organic solvents (oils, fats)
  5. 5. Movement through Environment Accumulates in the hydrosphere, the organic fraction of soil, and in organisms Oceans dissolve a significant quantity of PCBs Detected in atmosphere of urbanized areas Found in regions north of Arctic Circle Atmosphere is the primary route of global transport
  6. 6. Movement into Cells Binds to aryl hydrocarbon receptor (AhR)  Alters the transcription of genes Commercial PCB formed triacylglycerol-like droplets that accumulate in hepatocytes Mode of uptake is through hydrophobic domains of lipids for the transport of PCBs by plasma fractions  Accumulates in adipose tissue
  7. 7. Major Sources Landfills containing transformers, capacitors, and other PCB waste Incineration of municipal waste Evaporation from contaminated water bodies Wastewater effluent Scrap metal recycling (heat transfer and hydraulic equipment) Used oil (<50 ppm) Asphalt roofing materials Auto salvage yards (hydraulic fluid, ignition coils)
  8. 8. Toxicity Maximum containment levels in drinking water mandated by the EPA is 0.5 ppb 2,3,7,8-tetrachlorodibenzo[p]dioxin is assigned a toxic equivalency factor of 1
  9. 9. Environmental Damage Classified as a persistent organic pollutant  Bioaccumulation Does not decompose readily Long half life of 8 to 10 years Generates toxic dibenzodioxins and dibenzofurans Damages animal life  Liver damage  Hepatocarcinoma  Impaired reproduction
  10. 10. Health Effects Endocrine disruption Neurotoxin Skin conditions, such as chloracne or rashes Fatigue, headaches, coughs, unusual skin sores Ocular lesions, irregular menstrual cycles, lowered immune response
  11. 11. Link to Cancer Imitates estrogen compound and can feed breast cancer cells Linked to cancer of the liver and biliary tract Department of Health and Human Services conclude PCBs are anticipated to be carcinogens