Midterm 1 (Lectures 1-5) Flashcards
What are the 3 general principles of toxicology?
- You can only find what you’re looking for
- The dose makes the poison
- Only living material can measure toxicity
What is the purpose of the Canadian Council of Animal Care?
to ensure that animal based science in Canada takes place only when necessary and the animals in the studies receive optimal care
What are the 3 main categories used by agencies in evaluation & regulation of toxic chemicals?
- Human epidemiology
- Human controlled clinical exposures
- Plant and non-human animal toxicity tests
What is the purpose of ecotoxicity testing?
To provide data that can be used to establish safe concentrations of toxicants that will not cause adverse effects on ecosystems and evaluate toxicity samples collected from contaminated sites.
Environmental Toxicology can be simplified to the understanding of 3 functions:
- f(f) to describe the fate and transformation of the xenobiotic
- f(s) to describe the interaction of xenobiotic with the site or sites of action
- f(e) to describe the effects of the xenobiotic upon the biotic and ecological structures
5 parameters that must be understood to explain xenobiotic effects at ecosystem level:
- introduction of contaminant
- physiological and behavioural parameters (chromosomal damage, tumours, tertogenic effects
- community parameters (structure, diversity, trophic complexity)
- biochemical parameters (stress proteins, metabolic indicators)
- population parameters (population density, population range, age density)
What toxicity tests are single species?
Acute and chronic
What toxicity tests are multi species?
Microcosms, mesocosms, field studies
Principles of chronic toxicity tests:
Sublethal, longer (more significant portion of the organisms lifespan), more complex, more expensive
What are some examples of endpoints for chronic toxicity tests?
Behaviour, carcinogenesis, organ damage, growth, reproduction
Describe analysis of variance
hypothesis testing - test for significant difference from control and between all treatment groups
Where are acute and chronic toxicity test methods available?
- American society for testing materials
- Organization for economic cooperation and materials
- National toxicology program
- Environment canada
Name 5 advantages of standard methods
- tests are uniform and comparable to previous results
- can be replicated/confirmed by other laboratories
- data generated can be combined with those from other laboratories
- detailed listing of apparatus, dilution water, test material, test organisms
- can rank potency of chemicals because of uniformity of tests
Name 3 disadvantages of standard methods
- Often very specific, hard to apply to other situations or answer other questions
- may not be applicable to natural environment
- currently mainly single chemicals only, however there may be multiple chemicals combining in the real world. Can’t understand what the combination of chemicals does
Compare and contrast acute and chronic toxicity tests
Chronic:
- Sub lethal (growth, reproduction)
- More ecologically relevant
- Shows effect at much lower dose = designed to determine sub-lethal effects
- More labour intensive, takes longer, more expensive
Acute:
- drop dead testing
- time = 2 days (invertebrates) to 4 days (fish)
- LD50: often terrestrial, we know exactly what dose is being given
- EC50: effective concentration, lose equilibrium, sit on bottom = ecologically dead
- Not very ecologically relevant but quick, relatively cheap
- Rank hazards = lower LC50 = more toxic
- Usually precursor to chronic toxicity testing = useful in designing chronic toxicity tests
What makes a good test species?
- lab hardiness
- common
- known life cycle
- cheap
- short lived
Name 4 test organisms used in mammalian tests
- rodents
- mini pigs
- primates
- dogs
Define environmental quality guidelines
Numerical concentrations or narrative statements that are recommended as levels that should result in negligible risk to biota, their functions, or any interactions that are integral to sustaining the health of ecosystems and the designated resources they support
List 3 fields that include environmental toxicology
- environmental science
- classical toxicology
- eco toxicology
What was DDT used for and how did it impact the ecosystem?
DDT was used as an insecticide/agricultural pesticide and malaria/typhus control agent.
DDT kept sodium ion channels open in insects and wildlife causing constant stimulation of nervous system leading to death. Birds of prey suffered from egg shell thinning and poor survival of offspring as DDT impacted the eggshell gland and proper hormone synthesis. Gland couldn’t produce hard eggshells
What is the current status of chemicals and the environment?
- chemicals are known
- chemicals produced/manufactured deliberately
- chemicals produced at >1 tonne per year
What is the cause+effect pathway?
Pollutant -> biochemical changes -> physiological changes -> whole organism responds -> population changes -> community composition -> ecosystems
Name 2 ecosystem relationships
- interactions with physical aspects of environment
- interactions with same and other species
What are some causes of current species extinction?
- agriculture
- deforestation
- overharvesting ocean wildlife
- invasive species
- climate change
What is a community?
a group of species that occupy a given area, interacting either directly or indirectly
Name 4 community attributes
- # of species
- relative abundance of species
- nature of species interactions
- physical structure (habitat)
List 5 effects of an exotoxicology analysis at the population level
- Species abundance
- Reductions or increases beyond natural fluctuations
- Reproductive success
- Alterations in genetics
- Likelihood of extinction
List 4 effects of an exotoxicology analysis at the community structure level
- reductions/increases in community structure
- Biodiversity changes
- Species abundance/dominance
- predator/prey interactions
List an effect of an exotoxicology analysis at the ecosystem level
- Changes in ecosystem processes (primary production, total system respiration, decomposition, nutrient cycling)
List 2 effects of an exotoxicology analysis at the landscape level
- Spatial distribution/extent of different habitat types within landscapes
- Changes in size, shape, proximity of different habitats
List 2 factors to increase or decrease risk
- hazard: the harm that something will cause
- exposure: extent organism/environment is subjected to the hazard
Define ecological risk assessment
assesses probability of a given adverse effect as a result of a human activity. Requires good knowledge of the properties and effects of the chemical in question in complex ecosystems
Name 2 of the 5 questions that ecological risk assessments answer
- could these concentrations cause any harm?
- should we and could we reduce this risk?
What are 3 points of the current dogma of ecological risk assessments?
- cost of elimination of chemicals is impossibly high
- decisions must always be made on the basis of incomplete information
- currently use ~100,000 chemicals but only know ~1% of what we need to know
What is the goal of multi species toxicity tests?
To indicate potential population and higher adverse effects of toxicant. Attempt to recreate complexity of natural systems
Compare and contrast microcosm and mesocosm
microcosm:
- Multiple species
- Functional and structural endpoints
- Not all trophic levels
- E.g. <15m3 of water
- Easier to increase replicates
mesocosm:
- Multiple species
- Functional and structural endpoints (more endpoints)
- More trophic levels (no top level predators)
- E.g. >15m3 of water
define limnocorrals (include differences between sealed and not sealed)
Enclosures placed in natural lakes/water bodies. Sealed = controlled addition of toxicant. Not sealed = control site vs. contaminated site
what is an advantage and a disadvantage of a limnocorral?
A: native and developed communities within natural system, not lab bred
D: inclement weather and destruction of corral/organisms
Define artificial stream and the difference between lotic or lentic
Lotic = flowing, lentic = nonflowing
Aquatic exposure stocked with organisms or organisms are allows to enter from natural waters. toxicant is added to water and functional and structural effects are monitored
What are the two types of field surveys?
- baseline or pre-exposure and post exposure monitoring for adverse effects in wild organisms
- real-time whole organism (biomonitoring) = use of transplanted organisms an sentinels in the environment
Define adverse outcome pathways
new approach to describe sequential chain of casually linked events at different levels of biological organization that lead to health effects on organisms
List 3 locations where toxicant may affect organism
- whole organism
- protein
- gene
What is the adverse outcome of acid rain?
pH of 5.6 lead to calcium depletion. Daphnia can’t live in low calcium environments and loss of daphnia = loss of organisms that consume daphnia. Causes loss of calcium from soils and watersheds
How often is environmental effects monitoring conducted and how is it tested?
every 3 years unless no effects, then every 6 years. Tested by sub-lethal toxicity testing of effluent and field surveys
List 3 ways pollutants and contaminants can enter the ecosystem as a result of human activity
- unintended release from human activities (nuclear accidents, shipwrecks)
- disposal of wastes (sewage and industrial effluents)
- deliberate applications (pest and vector control, fertilizers)
Define primary, secondary, and tertiary sewage treatment
primary:
- sedimentation to remove suspended solids
- screening to trap solids
secondary:
- microbes+O2+mix to remove dissolved organic matter and convert to CO2, water and energy for growth
- settling tanks for secondary sedimentation
tertiary:
- UV, chlorination, ozonation
List 3 major routes of land contamination and the pollutants associated with them
- waste dumping: wide range of pollutants
- pesticides: insecticides, rodenticides, fungicides, herbicides
- application of sewage to agricultural land: heavy metals, nitrates, detergents
list 4 major routes of atmospheric contamination and their associated pollutants
- domestic chimneys: organic compounds
- chimneys of industrial plants, power stations etc: same as domestic chimneys + other pollutants depending on what the site does
- internal combustion of jet engines: CO2, hydrocarbons, lead
- pesticide applications: insecticides, fungicides, herbicides
List 5 descriptors about metals
- many are global pollutants
- conductive
- reactive/form compounds with other elements easily
- catatonic tendency in solution (generally make positive ions when dissolved)
- tendency to combine (alloys are mixtures of metallic elements)
Name 3 sources of metals
- naturally occurring in the earth’s crust
- mining and smelting
- not biodegradable
What is biotic ligand model?
use to predict the degree of metal binding at the site of action (biotic ligand), this level of accumulation is in turn related to toxicological response
Metal toxicokinetics is not fully understood, name 3 things the metal ion might do
- bind to metallothionein: renders it non-toxic
- deposition into insoluble forms in intracellular granules for longer-term storage or incorporation into biomolecules
- excretion in urine/feces
Do animals need copper?
Yes, copper is a micronutrient in most organisms (hemoglobin, metabolism etc)
what is wilson’s disease and how is it treated?
Wilson’s disease is a mutation in the gene that codes for copper transporting P-type ATPase that excretes excess copper into bile and plasma. Leads to liver disease if untreated. Treatment is chelation with copper chelation
