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POLYCHLORINATED BIPHENYLS (PCBs). By Jenn Corpuz. PHYSICAL & CHEMICAL PROPERTIES. C 12 H 10-x Cl x MP: 340-375 C Thin, lightly colored liquids to yellow or black waxy solids. picture from: www.epa.gov. PRODUCTION HISTORY. Developed in 1929 Multiple congeners developed - PowerPoint PPT Presentation
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POLYCHLORINATED BIPHENYLS
(PCBs)
By Jenn Corpuz
PHYSICAL & CHEMICAL PROPERTIES
C12H10-xClx MP: 340-375 C Thin, lightly colored
liquids to yellow or black waxy solids
picture from: www.epa.gov
PRODUCTION HISTORY Developed in 1929 Multiple congeners developed Used as a coolant for electrical equipment and as a
plasticizer in paints, plastics and rubber products Banned by EPA in 1979 Products manufactured before 1979 are still releasing
PCBs into the environment Most commonly known as: Aroclor, Phenoclor and
Kanechlor
MODE OF ENTRY INTO AQUATIC ENVIRONMENT
Run off Poorly maintained hazardous waste sites
containing PCBs Burning of wastes in municipal or industrial
incinerators
CHEMICAL REACTIVITY 209 known congeners
(species) Most common: Aroclor,
Phenoclors, Kaneochlors
Most toxic: coplanar mono-orthosubstituted species
Figure by Safe et. al.
CHEMICAL REACTIVITY (cont’d) Most species: insoluble in
water Solubility decreases with
increasing chlorination 0.01-0.0001ug/L Halflives: 3 wks -2 yrs (air) <6 yrs (aerobic
soils/sediments)picture from: www.epa.gov
TOXICITY TO AQUATIC LIFE Sediment bound Bioaccumulated and magnified through the
food chain Rainbow Trout LC50= 0.32ug/L
Laboratory Rats LD50= 1g/kg by weight Acute toxicity generally low Chronic toxicity gave results
TOXIC EFFECTS NOTED PCBs are known carcinogens Found to be highly associated with cancers
in the immune, reproductive and endocrine systems
Iipophilicity allows PCBs to live in animal’s tissues
MODE OF ENTRY Ingestion (most common)
gills
MODE OF INTERACTION Induces AHH and
binds to AhR Binds ARNT Leads to gene
transcription PCBs have been
linked to activation of oncogenes and inactivation of tumor suppressing genes
BIOCHEMICAL METABOLISM AND BREAKDOWN
CYP1A and CYP1B are induced
Resulting hydroxylated and methylsulfonyl PCB metabolites bind to DNA
Highly chlorinated biphenyls are metabolized very slowly if at all
Phase II (excretion) is unlikely
Figure from Tabb et. al.
DEFENSE STRATEGIES FOR DETOXIFICATION
For less chlorinated species: oxygenating chlorine sites excretion through urine
None for highly chlorinated species
BIBLIOGRAPHY www.epa.gov
www.ehponline.org
Hansen, Larry G. “Stepping Backward to Improve Assessment of PCB Congener Toxicities.” Environmental Health Perspectives. Volume 106. Feb 1998.
McConnell, Ernest. “Comparitive Toxicity of PCBs and Related Compounds in Various Species of Animals.” Environmental Health Perspectives. Volume 60. 1985. 29-33.
Neal, Robert A. “Mechanisms of the Biological Effects of PCBs, Polychlorinated Dibenzo-p-dioxins, and Polychlorinated Dibenzofurans in Experimental Animals.” Environmental Health Perspectives. Volume 60. 1985. 41-46.
Safe, Stephen, Stelvin Bandiera, Tom Sawyer, Larry Robertson, Lorna Safe, Andrew Parkinson, Paul E. Thomas, Dene E. Ryan, Linda M. Reik, Wayne Levin, Mary Anne Denomme, and Toshio Fujita. “PCBs: Structure-Function Relationships and Mechanism of Action.” Environmental Health Perspectives. Volume 60. 1985. 47-56.
Tabb, Michelle M., Vladyslav Kholodovych, Feliz Grun, Changcheng Zhou, William J. Welsh, and Bruce Blumberg. “ Highly Chlorinated PCBs inhibit the Human Xenobiotic Response Mediated by Steroid and Xenobiotic Receptor (SXR). Environmental Health Perspectives. Volume 112. 163-169.
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