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Lecture 4

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University of Waterloo
BIOL 354
Bruce Greenberg

BIOL354 – Environmental Toxicology I Spring 2012 Lecture 4: Organic Pollutants - Review: Ammonia toxicity is modified abiotically primarily by pH & secondarily by temperature, they are the parameters that change the [un-ionized ammonia] (increase/decrease in [H ions]) - Sydney Tar Ponds: o Canada’s LARGEST contaminated site (700 000 tonnes of PAH with 5% PCBs) o 90 years of steel making discharge consisting of volatilized or liquid solvents (coal tars) produced during coke production that contains BTEX (significant # of PAHs).  PAHs (Polysistic aromatic hydrocarbons) naturally found in crude oil & coal deposits.  Heating fuels releases more PAHs. o 0.5 tons/m2 particulate within 3km radius -> NATIONALLY HIGHEST cancer mortality rates. o $400 million on site remediation to solidify & stabilize the ponds, sediments & soils. o Estimated time span: at least 25 years, even after 25 years, S/S treated sediment must be maintained separated from both the surface & the drinkable ground water. o If unsuccessful, costly alternative: excavate & treat sediments offsite. - Organic Pollutants: Carbon-based, structurally diverse, usually w/ low persistence & degrades easily, but exceptions exists (Persistent Organic Pollutants/POPs) because they are being synthesized synthetically. o No general classification, can be classified based on chemical structure, physical property etc. o Petroleum Hydrocarbons (PHCs):  Mixture of organic geological substances (e.g. oil, bitumen & coal).  Provides energy, fuel, lubrication, power, & are sources of synthetic plastics.  Lipophilic, persists in soils (approx 60% of Canada’s contaminated sites).  Based on the compounds’ molecular weight:  Lighter Hydrocarbons: More valuable, toxic, volatile & mobile. Due to their lipophilic nature, can be a problem @ distances away from point of release  Heavier Hydrocarbons: More absorbed into sediments, more persistent & are less bioavailable compare to lighter MW. o Bioavailable: absorption across membrane from environment into the organism’s blood stream (Intravenously: 100% bioavailable) o Polycyclic/Polynuclear Aromatic Hydrocarbons (PAHs):  2+ FUSED aromatic (benzene) rings (very stabilized structures) -> persistency  Produced by burning of organic material (especially incomplete, low temp combustion of C-containing fuels such as oil, wood, coal, tobacco, & fats)  Natural: Volcanoes & Forest Fires  Anthropogenic: Fossil fuel, smoke stacks, automobile exhaust, tobacco,& metal refining  Higher levels @ big cities, increased potential for exposure  Grilling sausages: high level of PAHs production, likely carcino/muta/teratogenic  Highly lipophilic, rapidly stored in lipids (biotic) or into sediments (abiotic)  16 Priority PAHs  Low MW PAHs: 1-3 benzene rings  High MV PAHs: 4+ benzene rings, less volatile & more lipophilic  Easily absorbed by soils, but still readily bioavailable to aquatic organisms (bio-meg/accu)  Easily accumulates airborne/waterborne PAHs  Higher Vertebrates: most PAHs don’t accumulate (rapidly metabolize & excrete) o Parental PAHs are unreactive, but reactivity/toxicity can be altered through metabolism [Post-Ingestion-Modification] o Polychlorinated biphenyls (PCBs): [ALL ANTHROPOGENIC (Synthetic “man-made”)] BIOL354 – Environmental Toxicology I Spring 2012  Highly lipophilic, low acute toxicity, & are chlorinated organics  Chemically inert: Stable, inflammable/non-volatile, non-conducting, & hydrophobic  Widely used as fluid insulators, flame retardants, & hydraulic fluids  Chronic effects after long term exposure: effects endocrine system  209 congeners (differentiated based on number & position of Cl atom) o Dioxins & furans: [Dioxin-like & furan-like chlorinated organic compounds]  Lipophilic, w/ high bioconcentration factors (BCFs)  Not directly produced, but are by-products of chlorination/bleaching processes  E.g. pulp & paper mills, or production of PCBs, lampricides & pesticides  Not easily metabolized or excreted due to high degree of chlorination  Toxicity increase by binding to the Aryl Hydrocarbon (AH) receptor, which can induce alterations in gene expression (cytochrome P450 dependent genes) o Not directly linked to associate endocrine dysfunctions  Polychl
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