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80 Cards in this Set
- Front
- Back
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What are the 10 factors affected toxicity?
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dose/concentration
route of uptake liphilicity exposure time and animals size biotransformation potential presence of target sites life stage volatility/chemical stability environmental conditions bioavailability |
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old paradigm for pollution -
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dilution is the solution for pollution
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boomerang paradigm
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the problem will come hit us back in the face
-eg DDT -mercury poisoning in fish - birth defects |
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toxicant
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poison, substance causing illness, injury or death by chemical means
-any compound can be a poison depending on the dose |
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contaminant
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chemicals exceeding environmental background levels
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pollutant
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chemicals exceeding environmental background levels and potentially causing harm
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xenobiotic
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substance that is foreign to an organism
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environmental toxicology
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study of nature, properties, effects, and detection of toxic substances in the environment and in environmentally exposed organisms
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ecotoxicology
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study of the adverse effects of environmental contaminants on biological systems
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what are 4 ways that humans can increase the bioavailability of elements?
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-release from lithospere into biosphere
-redistribution in the biosphere -changing form of elements (eg from Cr-3 to Cr-6) -changing environmental conditions (decreasing pH, changing temperature) |
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Mercury
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-neurotoxin
-most applications obsolete, but still used in gold mining |
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Cadmium
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-mimics Zinc
-binds strongly to ligands (especially S containing) |
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Lead
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-mimics Calcium
-very malleable, heavy, low melting point |
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Copper
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-used in alloys
-good conductor -used as pesticide |
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Nickel
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-used in alloys to prevent corrosion
-some nickel compounds are carcinogenic |
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Chromium
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-occurs as Cr-3 and Cr-6
-used in alloys, as anti-corrosive, paints |
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Tin
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-very malleable, low melting point
-used as metal, anticorrosive -organo-tin compounds are of most concern (TBT = tri-butyl-tin) |
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Arsenic
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-bangladesh (high levels in groundwater)
-poison (napoleon?) -wood preservative, alloys |
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Halogens
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-F2, Cl2, Br2, I2
-when bound to organic compounds, they increase the persistence and toxicity of those compounds |
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Phosphorous
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-nutrient
-fertilizer (phosphate) (can cause algal blooms and eutrophication) |
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Nitrogen
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-nutrient
-fertilizer (nitrate, ammonium) (eutrophication) -as NOx is major air pollutant, causes smog |
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Sulfur
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-ancient pesticide (allowed in organic farming)
-preservative -SO2 released from coal burning, causes acid rain (becomes sulfuric acid) |
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Radioactive Pollutants
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decay to form eventually stable elements while emitting
-alpha radiation (He ions) -beta radiation (e- or e+) -gamma radiation (photons) -neutrons |
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Nanoparticles
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-size in nanometer range
-size and shape determine toxicity -large increase in productions, applications -ZnO -TiO2 |
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Four factors of concern with organic compounds :
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(1) Polarity (lipophlicity)
(2) Persistence (compounds that degrade poorly) (3) Halogens (they increase toxicity and persistence of organic compounds) (4) Toxicological hazard (interfere with biochemical and physiological processes) |
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Aromatic hydrocarbons
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-low polarity, accumulate in sediments
-volatile (chlorinated hydrocarbons act differently) |
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Chlorinated Hydrocarbons
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-highly lipophilic
-very persistent |
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Biphenyls
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PCPs (polychlorinated biphenyls) are very persistent, very lipophilic
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Dioxins
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-byproducts of chemical reactions
-highly persistent -high bioaccumulation potential |
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DDT
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-very persistent
-highly lipophilic -pests can develop resistence -decay into DDE and DDD (these are the persistent ones) -is an Organochlorine Pesticide |
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Organo-phosphorus and Carbamates
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modern insecticides
-neurotoxins (mostly for invertebrates) -low persistence -acute toxicity |
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Pyrethroids and Neonicotinoids
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modern insecticides
-neurotoxins (low for mammals and birds, high for fish and invertebrates) -rapidly biodegrades |
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Triazines
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herbicides
-inhibitors of photosynthesis -atrazine is endocrine disruptor, associated with amphibian decline |
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Glyphosphate
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herbicides
-disrupts protein synthesis in plants -round up -may be endocrine disruptor |
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What are 4 factors determining the fate of pollutants?
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-Polarity
-Volatility (low boiling point) -Chemical stability -Environmental conditions (pH, Temp, Redox potential) |
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What are the major environmental compartments?
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-water
-air -soil -sediment -biosphere |
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Ways in which organic compounds can be degraded :
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-Photodegradation
-Oxidation (compound is e- donor) -Reduction (compound is e acceptor) -Hydrolysis (compound breaks into two parts - one side receives H, the other OH) -Biodegradation |
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Main uptake routes for pollutants in organisms :
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-alimentary tract (GI tract)
-respiratory surfaces -skin -leaves and roots |
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Elimination of pollutants is achieved via :
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(1) Gills - removal of lipophilic comounds
(2) Feces - removal of metals by shedding gut lining, removal of lipophilic compounds with bile (3) Urine - removal of lipophilic compounds ad metals (4) Eggs and Milk - removal of lipophilic compounds (5) Molting, shedding - remoal of metals with exoskeleton, leaves, bark, hair, feathers |
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Toxicokinetics
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model for compartment exchange
-assumes animal is homogenous (one compartment) -doesn't consider biotransformation rate toxicant changes in body = rate toxicant enters - rate toxicants are removed from body |
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Kb =
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bioconcentration factor
= ku/ke = C(inf)/C(env) =0.04 Kow when log Kow is between 2 and 6 |
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in the accumulation and elimination graphs, the horizontal asymptote =
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The ultimate body burden :
C(inf) = Kb•C(env) |
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when ku increases,
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C(inf) increases
(but it doesn't take longer to reach the ultimate body burden) |
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when ke increases,
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lower ultimate body burden (C(inf)), but toxin accumulates more quickly
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body burden
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toxicant density or concentration
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Why is it important to measure the body burden instead of just the ambient concentration?
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-only a fraction of the pollutant may be bioavailable
-pollutants differ in accumulation potential -a pollutant may be chemically transformed once inside an animal -ambient concentrations are highly variable |
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Molecular toxicity can translate to :
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-reduced growth and reproduction rates
-lower population densities -altered community structures -changed ecosystem functioning |
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ways organisms neutralize/cope with pollutants :
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•Reparation
-response to stress - induction of stress proteins -general goal is to maintain homeostasis of stressors •Sequestering -metallothionins •Biotransformation -reducing lipophilicity, enhancing elimination |
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Biotransformation phases :
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Phase 1 transformation
-increasing water solubility by adding O or OH groups, breaking double bonds, removing groups Phase 2 transformation -increasing water solubility by adding polar groups like sugars, sulfate, glutathione |
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general toxicity
specific toxicity |
-multiple target sites in different tissues
-specific - a single site in specific tissue (eg neurotoxic compounds) |
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teratogenic effects
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-substances that can interfere with normal embryonic development
(sensitivity to toxin can depend on life-stage) |
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Intoxication Mechanisms
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(1) Genotoxic compounds - compounds that bind to DNA, may causes mutations when repair mechanisms fail
(2) Neurotoxic compounds - can affect signal transduction (3) Vitamin K antagonists inhibit production of clotting proteins (4) Mitochondrial poisons (5) Chloroplast poisons (6) ATPase inhibitors (osmoregulation) (7) Non-competitive inhibition of enzymes (8) Plant growth hormone analogues (9) Endocrine disruptors |
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Interactive effects of pollutants in an organism:
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(1) Additive Effects - net toxicity is the sum of the toxicities of individual pollutants (most common effect)
(2) Antagonistic Effects - net toxicity is less than the sum of the toxicities of the individual pollutants (3) Synergistic Effects (potentiation) - net toxicity is greater than the sum of the toxicities of individual pollutants |
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Potentiation
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(synergistic effects)
(1) Inhibition of detoxification -one compound inhibits enzyme system that detoxifies another compound (2) Stimulation of activation -one compound induces the expression an enzyme system that activates toxicity of another |
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Toxic effects on organism level :
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(1) Sublethal - reduced feeding/photosynthesis, higher maintenance costs, lower growth and reproduction rates, reduced vitality or reproductive matter, develpmental disorders
(2) Lethal - acute, chronic, increased risk of predation/infection |
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Scope for Growth
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Type of energy budget
-low tech, easy to interpret, nonspecific biomonitoring tool -shows actual impact -lacks interpretive power |
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what is the drawback of Scope for Growth?
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Is purely descriptive, lacks interpretive power :
-multiple stressors? -link to physiological effect? -could be interpreted incorrectly -can't apply information to other pollutant levels -other effects (viability? mortality?) |
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Dynamic Energy Budget Theory
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Type of energy budget
-very math oriented -used to make predictions -analysis tool with wide application potential -show actual impact -has interpretive power |
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acute toxicity tests
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lasts between 1-3 days
-end point is usually mortality -yields info about proper pesticide application dose and acute toxic effects -problem - bioaccumulation may not be complete - results depend on experiment duration |
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chronic toxicity tests
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experiment last more than 1-3 days, less than lifespan
-any end point -results more relevant for environmental risk assessment than acute toxicity tests |
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life cycle tests
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-experiment lasts several generations
-any end point |
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microcosm
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a few small species (foodchain) in a relatively small, controlled enclosure
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mesocosm
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multiple speces, potentially including a vertebrate, in medium sized, controlled enclosure
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LC50
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concentration at which 50% of test animals survive
(Lethal effects) |
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EC50
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concentration at which end point is 50% of control
(Sublethal effects) |
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LOEC
NOEC NEC |
lowest observed effect concentration
no observed effect concentration no effect concentration |
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Biomarker
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any biochemical, physiological, morphological, behavioral or energetic response in individual organisms to an environmental pollutants
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Bioindicator
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any response on the level of population, communities or ecosystems to an environmental pollutant
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Ecological indicator
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any response of biological systems to environmental stressors
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Environmental indicator
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any biological, chemical, or physical response of a system to environmental stressors
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Types of Biomarkers
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(1) Physiological Biomarkers
-imposex, feminization, egg shell thinning -relatively clear link between response and pollution -better link between response and performance of individual, population, community, ecosystem (2) Whole Organism Biomarkers -scope for growth, reproduction, mortality, behavior -may respond to many environmental stressors, not just pollution. -best link between response and performance of individual, population, community, ecosystem |
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Specificity of Biomarkers
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•Specific to Pollutants
-respond to one or a few pollutants •Non Specific to Pollutants -respond to a variety of pollutants •Specific of Adverse Effects -response variable clearly links to effects at higher levels of organization •Non Specific of Adverse Effects -difficult or impossible to predict effects at higher levels of organization |
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Types of Biomonitoring
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•Type 1 Biomonitoring - community effects
•Type 2 Biomonitoring - bioconcentration •Type 3 Biomonitoring - effects on Biomarkers •Type 4 Biomonitoring - resistant strains |
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Type 1 Biomonitoring
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Community Effects:
-species composition -species richness -species abundance (insensitive to loss of rare species, or to species replacement) |
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Type 2 Biomonitoring
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Bioconcentration
-bioaccumulation -eg mussel watch |
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Type 3 Biomonitoring
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Effects on Biomarkers
•commonly used biomarkers in biomonitoring: -scope for growth -monooxygenase induction -metallothionin inductin -acetylcholinesterase inhibition -egg shell thickness |
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Type 4 Biomonitoring
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Development of Resistance
-tolerance to metals: plants, soils, arthropods -resistance to pesticides: insects |
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Why is it difficult to discern effects of stress on real populations?
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(1) There are multiple stressors, some density dependent, some density independent
(2) Intensity of stressors varies over time (3) Population growth may be discrete (4) Real populations are age/stage structured: birth and death rates depend on age/stage (5) Dynamics of real populations depend on biotic interactions (6) A population may develop resistance to a stressor |
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Fluctutations in populations can be a result of :
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-environmental variability (seasonal)
-discrete population growth (stable limit cycle) -predator prey dynamics |
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How can you "prove" that observed effects at higher levels of organization are caused by pollutants?
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Three Possible Approaches:
(1) Apply mathematical models to translate effects at the biochemical level to population, community, or ecosystem level (2) Conduct large scale mesocosm, field enclosure or field trials with varying pollutant levels including controls (is elaborate, time consuming, expensive) (3) Use 'mechanistic' biomarkers with effects that are quantitatively 'calibrated' to population effects |
