Exam 3 Flashcards
BAF or BCF
BAF = conc of the organism in the enviroment/conc in the ambient enviroment
- Can be used to evaluate the effectiveness of a plant in metal accumulation and evaluate their potential use in metal remediation.
Factors from BAF
- pH , lower pH=higher BAF
- Organic matter content , lower OM content =higher BAF
- Clay content, lower clay content =higher BAF
- Cation exchange capacity , higher CEC =higher BAF
Bioaccumulation
Accumulation of substances in an organism
Occur when a organism absorped a substance at a rate faster than that at which the substance is lost by catabolism and excretion
Biomagnification
Concentration of toxin in an organism as a results of its ingesting other plants or animals in which the toxins are more widely disbursed.
Concentration increase with the trophic level.
Bioavailability
Fraction of ingested metal absorped into the systemic circulation
Bioaccessibility
Fraction of total metal that dissolves in the stomach and is available for absorption during transit through the small intestine
Kow
Kow=conc in octanol/conc in water
Below 1:High water solubility, low lipid solubility
Above 1: High lipid solubility, low water solubility
Is an important factor to understand the fate of an organic compound in ecosystem
Passive diffusion
- Organic molecules - there croess natural barriers
- Molecules must have som affinities with the barrier it self some affinity for the water that lies to the inside of the barrier.
- Molecules should have a resonable balance between lipid solubility and water solubility
Lipophillic xenobiotics in living organism
Identifies five types of sites
- Uptake
- Metabolism
- Action
- Storage
- Excretion
Toxicokinetics
- Include processes of uptake, distribution, metabolism
- Determine how much of a toxic compound reaches the site of action
Toxicodynamics
- Molecular interactions at the site of action
- Determine by the nature and degree of interaction between the toxic compound and the site of action
Phase 1
- Oxidation, hydrolysis, hydration, reduction
- Production of metabolites that contain OH-groups
- A polar group is either introduced or unmasked so the drug molecule becomes more water soluble and can be excreted
- Produce a water-soluble and less active metabolites
- Mocrosomal monooxygenase enzyme
phase 2
- Conjugation reaction
- Most conjugates are negatively charges and are readily excreted in bile or urine
- Sulfotransferases
Enzymatic metabolism of most lipophillic compounds
-Occurs in 2 phases
Xenobiotic -> Metabolite -> Conjugate
Phase 1 Phase 2
Half-life
Determine the time it takes to metabolize / eliminate 50 % of the drug or the compound from the body or plasma
First order kinetic
- Proportional
- Half-life is constant
- Rate of elimination is not constant
Zero order kinetic
- Half-life is not constant
- Rate of elimination is constant
Additivity
A combination of two or more chemicals is the sum of the expected individual response
A=20
B=30
A+B=50
Antagorism
Exposure to one chemical results in a reduction in the effect of the other chemical
A=20
B=30
A+B=5
Potentiation
Exposure to one chemical results in the other chemical producing on effects greater than if given alone
A=0
B=20
A+B=50
Synergism
Exposure to one chemical causes a dramatic increse in the effect of another chemical
A=5
B=10
A+B=100
OECD
- Internationally accepted guidelines as standard methods for safety testing
- Include earthworms toxicity testing standard protocols
- Are uses by professionals in industry, academia, and government involved in the testing and assessment of chemicals
Risk assessment
Risk quotient = PEC (predicted enviromental concentration) / PNEC (predicted enviromental no effect concentration)
Risk ratio >1 => Potential risk
Risk ratio <1 => Risk is low
-Combines on exposure assessment and a hazard identification
Alternative methods for ERA
- Use of microcosm and mesocosm studies
- Use of predictive models
- Use of vitro techniques
- Field studies
- Using live vertebrates
- Modeling work
Protective biochemical response
- Induction of monooxygenase enzymes => metabolites
- Induction of MT - binding protein
- Response that correct damage after it has occured
- Induction od stress protein
- DNA repair
- Conjugate by glutathione S-transferase
Biomarker for endocrine disruption
- Aromatase
- Vitellogenin
Kidney to toxic injury
- Chemicals in the systemic circulation are delivered to the kidnet in relative high amount
- Kidneys concentrate potential toxicants during the urine formation process, particularly exposing toxic substanes to the tebular cells
Formation of DNA adducts
- Correspond to covalent binding of the pollutant wtih DNA
- Can be used as a biomarker of exposure of genetoxic compounds