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Polybrominated Biphenols: Structure, Properties, and Environmental Impact

Learn about the structure, physical and chemical properties of Polybrominated Biphenols (PBBs), their uses, historical production, mode of entry into the environment, chemical reactivity, toxicity effects on aquatic life and humans, and defense strategies against contamination.

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Polybrominated Biphenols: Structure, Properties, and Environmental Impact

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  1. Polybromated Biphenols Andrea Leasure BIOL 464

  2. Structure of the Compound

  3. Physical & Chemical Properties • Colorless to off-white solids • Low vapor pressure • Soluble in fat, organic solvents (solubility decreases w/ increasing bromine number) • Insoluble in water • Relatively stable & chemically unreactive • Photodegrade upon exposure to UV light

  4. Uses & Applications • Flame retardant additives in synthetic fibers & molded plastics. • Added to plastics to make them difficult to burn • Ex: Home electrical appliances, textiles, plastic foams.

  5. Production History • No longer produced in the United States (1976) • PBBs are still around in the environment because they do not degrade easily or quickly • Formerly produced in 3 primary forms: • Hexabromobiphenyl • Octabromobiphenyl • Decabromobiphenyl

  6. Production History • In 1973, several thousand pounds of hexabromobiphenyl were accidentally mixed with livestock feed in Michigan • 1.5 million chickens • 30,000 cattle • 5,900 pigs • 1,470 sheep • Bitter Harvest, 1981 film

  7. Mode of Entry in Aquatic Environment • PBBs entered the air, water & soil from • poorly maintained hazardous waste sites • Improper incineration of plastics containing PBBs. • Lower brominated PBBs are widely spread in the environment & bioaccumulate in aquatic biota • Higher brominated PBBs primarily bind to sediment & will hardly spread in aquatic systems or accumulate in biota.

  8. Chemical Reactivity • 209 congeners (congener pattern found in fish samples is different from that in commercial products) • 3,3',4,4',5,5'-hexaBB (BB-169) was found to be the most toxic PBB • Half-life in humans 7.8-12 years

  9. Toxicity to Aquatic Life • Exposed PBB water birds, nesting on islands in Lake Michigan, had no effect on reproduction. • Zebra mussels (Dreissena polymorpha) • Concentrations ranged from 0.85 to 22.44 (ng/g ww) with no effect • Freshwater Tilapia (Oreochromis niloticus ) • 6 h EC50 6.6 × 10−6 M • 24 h EC50 7.3 × 10−6 M

  10. Toxicity Effects • Reduction of feed consumption (decrease in body weight) • Causes skin disorders, nervous and immune systems effects, and effects on the liver, kidneys, and thyroid gland • Changes in the metabolism of vitamin A (retinol compounds and retinoic acid), which is important for cellular growth and differentiation

  11. Mode of Entry into Organisms • Gills • Ingestion • Breast milk

  12. Molecular Mode of Toxic Interaction • Induces CYTP450 • Induction of metabolic enzymes of hepatic microsome (arylhydrocarbon hydroxylase) • Interaction w/AHH receptors cause alteration in the expression in a number of genes.

  13. Biochemical Metabolism • Higher brominated PBBs are metabolized at a much slower rate than the lower brominated isomers. • The most frequently reported route of PBB metabolism was hydroxylation • aryl hydrocarbon hydroxylase (AHH system)

  14. Defense Strategies • Excretion through feces • Excretion through breast milk • Treatment to increase elimination of PBB in animals or humans was usually unsuccessful

  15. Bibliography • Primary cultured cells as sensitive in vitro model for assessment of toxicants- compasion to heptocytes and gill epithelia. Aquatic Toxicology, Volume 80, Issue 2, 16 November 2006, Pages 109-118 Bingsheng Zhou, Chunsheng Liu, Jingxian Wang, Paul K.S. Lam, Rudolf S.S. Wu • Microcontaminant accumulatoin, physiological condition and bilateral asymmetry in zebra mussels (Dreissena polymorpha) from clean and contaminated surface waters. Aquatic Toxicology, Volume 79, Issue 3, 12 September 2006, Pages 213-225 Judith Voets, Willem Talloen, Tineke de Tender, Stefan van Dongen, Adrian Covaci, Ronny Blust, Lieven Bervoets • http://www.inchem.org/documents/hsg/hsg/hsg083.htm Accessed April 17,2008 • http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s148pbb.pdf Accessed April 17, 2008 • http://www.atsdr.cdc.gov/tfacts68.html Accessed April 17, 2008 • http://www.michigan.gov/documents/mdch_PBB_FAQ_92051_7.pdf Accessed April 28, 2008 • http://www.ehponline.org/docs/1978/023/toc.html Accessed April 28, 2008 • http://www.meti.go.jp/english/report/downloadfiles/gED0306e.pdf Accessed April 30, 2008

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