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Arturo A. Keller
ESM 222
Classification of Pollutants
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Priority Pollutants
Amount Produced/ReleasedPersistenceBioaccumulationToxicityOther Effects
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Amount Produced or
ReleasedSome pollutants are produced in largeamounts but only released accidentally(e.g. chlorinated solvents, benzene)Others are released intentionally in largeamounts (e.g. pesticides)Some very toxic pollutants are onlyproduced in very small amounts (e.g.dioxins)
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Persistence
Resistance to transformation in theenvironment either chemical or biologicalPersistent chemicals can migrate widelyMeasured as residence time or as half-life Chlorinated/halogenated compounds aretypically persistent (e.g. DDT, PCBs, CFCs)
Rate of degradation depends on environmentalconditions
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Bioaccumulation
Uptake of pollutant by organismsDepends on hydrophobicity (i.e. water-hating), persistence and toxicity of pollutantConcentration may increase more than100,000 times from water to fishConcentration is biomagnified going upthe food chain
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Bioaccumulation
Sediments
Sea water
Fresh water
Sewage
Plankton
Aquatic invertebratesFishBirdsBird eggs
Marine Mammals
10 -7 10 -5 10 -3 10 -1 10 1 10 3 10 5
Concentration of total PCBs in ppm (mg/kg)
(from Pearson, 1982)
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Toxicity
Acute toxicity: concentration which kills 50% of a given
population (usually determined in lab) expressed as Lethal Dose to 50%: LD 50 ,
in units of mg chemical/kg body weight also depends on exposure
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Toxicity
Chronic toxicity Sub-lethal tests adverse effects: cease to feed, grow more
slowly, unable to reproduce or just abnormalbehavior
typically occurs at dosages 10 to 100 timessmaller than acute toxicity; more difficult,controversial & expensive to test
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Toxicology
Solvents as a general class Usually have high vapor pressures, so they
form vapors: major intake route is throughinhalation
Toxicity usually expressed as LD 50 in termsof air concentration
Most solvents depress the central nervoussystem => anesthetic effect
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Toxicology
Solvents CNS depression symptoms:
dizziness, confusionheadachesloss of coordination
convulsionscomadeath
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Toxicity
Genotoxicity Carcinogenic or mutagenic New tests are constantly developed, but
given low dosage and exposure, it is alwaysdifficult to determine increased risk
Short-term, high dosage test vs. long-term,low dosage in real life
Additional environmental factors alsogenotoxic
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Other Effects
Ability to influence large-scale biogeochemistry(e.g. CFCs, acid rain)
Alter availability of nutrients or other neededorganic chemicalsOdor (e.g. sulfur compounds, MTBE)Color (e.g. organic dyes)Foaming (e.g. detergents)Interfere with visibility (e.g. SO 2 particulates)
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Classification of Pollutants
What is the best criteria forclassification? Physical properties Chemical properties Chemical structure Effect on the environment
Organic vs. Inorganic
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Classification of Pollutants
Organic Chemicals Hydrocarbons Halogenated hydrocarbons Oxygenated hydrocarbons Nitrogen compounds
Sulfur compounds Phosphorus compounds
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Classification of Pollutants
Inorganic pollutants Arsenic Lead Copper Cadmium Mercury Chromium
Chlorine Cyanide Nitrate Ammonia
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Hydrocarbons
Formed by biogenic processes: microbes,vegetation, animalsContamination from oil spills, refineries,leaking USTs, fuel transport and useOnly slightly soluble in water, veryhydrophobic: Hexane about 10 mg/L = 10 g/m 3Linear hydrocarbons are easily degraded bymicrobes; branched are resistant
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Hydrocarbons
Hydrocarbons with double or triple bonds(alkenes, alkynes) are highly reactive: short lives in the environment
Aromatics: Fairly toxic (e.g. benzene, xylenes, ethylbenzene,
toluene) Considerably more soluble in water
(e.g. benzene = 1780 g/m3
)major concern for water supplies.
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Hydrocarbons
Fusion of benzene rings producespolycyclic aromatic hydrocarbons (PAHs)= polynuclear aromatic hydrocarbons(PNAs) Many are considered potential carcinogens.
benzo(a)pyrene
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Hydrocarbons
Effects on Living Organisms Physical
smotheringreduced lightinability to swim, fly, etcfur or feathers cannot function properly
Habitatdecrease dissolved oxygendecrease food availability
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Hydrocarbons
Effects on Living Organisms Toxicity of most hydrocarbons is usually low
at low concentrations, given theirbiodegradability
may affect internal organ functions (liver, kidney,etc) if ingested
PAH cause cancerous and non-canceroustumors in fish, reptiles, amphibians andmammals in lab studies
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Toxicology of Alkanes
Highly lipophilic so they target fatty tissueCNS depressantsDirect aspiration causes chemical pneumonitisConcentrated gasoline vapors cause cardiacarrhytmiaTypical half-life of hexane in body is 2h 10 days to remove hexane from fatty tissue
Some metabolites of hexane may cause otherfunctional disturbances
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Toxicology of AromaticHydrocarbons
Benzene and derivativesPrincipal exposure route is by inhalation30 to 80% absorbed by circulating bloodConcentrates in fatDestroys bone marrow and affects blood cellsConsidered a carcinogen (lungs, leukemia)
Acute exposure depresses CNS (3000 to 5000ppm)Higher concentrations cause death
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Halogenated Hydrocarbons
Halogens: Chlorine, Bromine, Iodine,Fluorine halogens are highly reactive as gases form very stable organic compounds
less flammablemore persistent in environment
less hydrophobic => more soluble inwater
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Toxicology of ChlorinatedHydrocarbons
Chloroform (CHCl 3)discontinued use as anesthetic in medicine due toeffect on liver and heartused in lacquers, plastics and refrigerantmanufactureexposure routes: inhalation, ingestion, dermalsuspected animal carcinogen (liver, renal)present in drinking water as a byproduct of chlorination to disinfect water
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Toxicology of Chlorinated
HydrocarbonsCarbon Tetrachloride (CCl 4)
anesthetic and antihelmintic agentused in dry cleaning and degreasingclassified as carcinogenacute exposure depresses CNSchronic exposure affects liver and kidney
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Trichloroethylene (TCE) (CHCl=CCl 2)dry cleaning, degreasing, solventused to extract caffeine from coffeediscontinued use as anesthetic in medicineclassified as carcinogendirect exposure irritates eyes, nose, throatacute exposure affects CNSchronic exposure affects liver and kidneys
Toxicology of ChlorinatedHydrocarbons
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Tetrachloroethylene (PCE) (CCl 2=CCl2)dry cleaning, degreasing, grain fumigantexposure routes: inhalation and dermalabsorptiondistributes through body, stored in fatsclassified as carcinogenacute exposure affects CNS
Toxicology of Chlorinated
Hydrocarbons
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Halogenated Hydrocarbons
Chlorinated aromatics biologically active, i.e. they interfere
with normal processes persistent useful as pesticides and disinfectants
Pentachlorophenol Chlorobenzenes, dichlorobenzenes
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Halogenated Hydrocarbons
Polychlorinated biphenyls (PCBs)Large family (209) of compounds
Very stable, used as electrical insulator fluids inpower transformers until ~ 20 yearsfluorescent light until 1970shydraulic fluids, brake fluids, heat transfer,plastizicers, lubricants, flame retardants
base for pesticides
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Halogenated Hydrocarbons
PCBspersistent and significant bioaccumulationlow acute toxicityincident in Japan in 1968 brought them attention(1291 individuals affected by contaminated riceoil)
from 1979 on, total ban on use of PCBs except incompletely enclosed systemsriver sediments are a major reservoir (e.g. UpperHudson, St. Lawrence)
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Halogenated Hydrocarbons
Fluorinated and chlorofluorinatedhydrocarbons are extremely stable best example is TEFLON, a fluorinated polymer
with extreme stability, temperature resistance andhydrophobicity (usually not a pollutant)
CFCs are used as refrigerants due to their stability.Their persistence in the lower atmosphere allowstransport to stratosphere where they interact withozone formation. Half-lives of decades in theatmosphere .
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Oxygenated Compounds
Alcohols (OH group) very widely used industrially usually water soluble usually highly degradable in the
environment
only an issue if spilled in large quantities large-chain alcohols (e.g. octanol) can besolvent for hydrophobic and hydrophilicorganics.
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Toxicology of Alcohols
Rapidly absorbed through lungs,gastrointestinal tract and skinDistributed through body tissues and fluidsCNS depressants at high doses (e.g. ethanol !)Methanol => formaldehyde => formic acid,which affect optic nerve, causing blindnessEthanol in large doses or repeated ingestioncauses hepatic or cardiac toxicity
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Oxygenated Compounds
Phenols aromatics with alcohol group may disrupt biological processes chlorinated phenols are particularly toxic
used in wood preservation (e.g. telephonepoles) which has led to widespreadcontamination of certain sites
Biodegradablemay be used to stimulate bioremediation
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Oxygenated Compounds
Esters, Ethers, Ketones & Aldehydes usually only a problem in atmospheric
pollution, where they contribute to ozoneformation in urban areas
fairly reactive in aquatic systems may be formed by incomplete combustion
industrial use is relatively small carcinogenicity of aldehydes
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Oxygenated Compounds
Organic acids usually quite reactive, so they are not of
major environmental concern
Dioxins and dibenzofurans form by oxidation/combustion of
chlorinated organics at high temperatures possibly the most toxic organics
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Nitrogenated organics
Amines, amino acids, proteins, etc. most are formed in biological processes can be quite toxic, but typically produced only in
small quantities biologically active but degradable some are formed during incomplete combustion
of fossil fuels (e.g. nitro PNAs) explosives manufacture and use (TNT)
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Pesticides
Organochlorines DDT, Methoxychlor, Aldrin, EndosulfanOrganophosphates Malathion, Parathion, Diazinon,
Chlorpyrifos, Glyphosate (Roundup)
Carbamate Esters Carbofuran, AldicarbPhenoxy Esters 2,4-D, Silvex, 2,4,5-T
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Pesticides
Also grouped by intended function:InsecticidesHerbicidesFungicidesRodenticides
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Inorganic Pollutants
Metals most are essential for biological activity
macronutrients: calcium, magnesium, iron,potassium, sodiummicronutrients: chromium, cobalt, copper,manganese, nickel, selenium, zinc
toxic in large doses mercury and lead form organometallic compounds
which disrupt normal biological processes
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Inorganic Pollutants
Natural releases via volcanoesHuman sources:
miningfuel combustion, cement productionfoundriesrefuse incinerationindustrial products, processes and waste
pesticides or fertilizers
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Toxicology of Metals
Arsenic Substitutes for phosphate, disrupting
metabolic processes (e.g. in ADP-ATP energycycle of cells)
Cadmium
Affects renal, pulmonary, skeletal, testicularand nervous systems Disrupts zinc-dependent enzymes
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Toxicology of Metals
Lead Inhibits hemoglobin synthesis => anemia Substitutes for Calcium, reducing cellular
functions (e.g. ATP production) Stored in bones, where it becomes a life-
long source of lead to the blood Organic lead compounds affect brain
function May cause lung cancer
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Toxicology of Metals
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Toxicology of Metals
Mercury Mercury vapors and organomercury enter
central nervous system Affects brain and nerve cells Sensory disturbance, reduced field vision
and ataxia
Impairment of speech, hearing and mentalfunctions
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Toxicology of Metals
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Inorganic Pollutants
Nitrate (NO -3) good fertilizer, toxic at high concentrations easily leaches out to rivers, ponds, lakes cause of lake eutrophication
Ammonia (NH 3) good fertilizer very toxic even at low concentrations
easily oxidized to nitrate in presence of O 2 in high concentrations affects pH of soil
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Biological Pollutants
Human pathogens
Medical Waste
Animal pathogens