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