Lecture 9 - DA Flashcards
Where did risk assessment originate from?
Insurance industry
Why are error bars necessary in biological statistics?
There is always inherent variability.
Why does ecological risk assessment consider non-human species?
More sensitive to environmental contamination, as non-human species have higher contact with pollutants, while humans have low contact.
Define ecological risk assessment.
Process that evaluates the likelihood that adverse ecological effects may occur or are occurring as a consequence of exposure to one or more stressors.
What is the consequence in an ecological risk assessment?
The hazard, which is the toxicant.
Name 2 ways to define risk (formula).
Risk = exposure x effect Risk = likelihood x consequence
Is risk always consistent? Give an example with zinc.
No it isnt.
Zinc has the same effect at a given concentration, but bioavailability will differ in freshwater systems compared to marine due to pH.
Why are LC50 tests done on the most sensitive species?
It would be useless to do it on tolerant species.
Define hazard.
Potential to cause harm.
Define risk.
Probability that harm will be caused.
What 2 factors are ecological risks based on?
Toxicity of a compound (ie LD50).
Anticipated exposure of an organism to that compound.
How are risk assessment endpoints developed?
In collaboration with stakeholders.
Define and explain the two categories risk assessment, and describe where the management focus is, and the degradation status.
Predictive - for proposed future actions
No degradation yet, focus is on prevention.
Retrospective - investigation of past activities that may have ongoing consequences.
Degradation has occurred and focus will be on remediation.
Define complications of inference.
Whether observations in the field are due to contaminants or another anthropogenic cause, or natural variability.
Whats more complex, human risk assessment, or non-human risk assessment?
Non-human risk assessment.
Define exposure assessment.
Estimate of the spatial and temporal dynamics of the concentration of the contaminant and its point of uptake by the organism.
What does an exposure assessment estimate? What does it model?
The properties of the contaminant, and degree of contact.
Models the processes of transport and its fate.
What 3 factors affect exposure to a contaminant?
Bioavailability
Multiple routes of exposure
Degree of relevance of lab data to the field
Whats more dangerous, overestimating or underestimating?
Underestimating.
What does an effects assessment establish?
Degree of exposure and the nature, severity, and duration of effects.
What are 5 problems with extrapolating from test endpoints to assessment endpoints?
- Test duration isnt predicted exposure duration
- Test species is not the same as endpoint species
- Tested life stages do not include all life stages
- Reported response doesnt include all of the response of concern
- Test endpoints are at organism level while assessment endpoints are usually population or ecosystem level
Name and describe the three approaches to extrapolation.
Multiply test endpoints by factors (safety factors, correction factors etc)
-Is simple but inaccurate
Use statistical models using mathematics
Risk characterisation
-Estimating the nature and likelihood of effects
What is the most common approach used for extrapolation?
Multiplying test endpoints by factors
What four dimensions can be defined in a risk characterisation? How many are commonly considered?
Defined duration of exposure
Defined concentration of pollutant
Defined proportion of organisms/populations/communities
Defined severity of exposure
Usually only one dimension is considered.
Describe a quantitative method of risk characterisation using a risk quotient.
Dividing estimated environmental concentration by a toxicological benchmark
If >1 then toxic effect is expected to occur - high risk
If <1 then toxic effect not expected - low risk
Define risk management. How is it performed in relation to risk assessment?
Process of reaching a decision concerning the appropriate course of action in a situation involving risk.
Performed independently of risk assessment.
What is the status of the environment in a retrospective risk assessment? Where does it begin?
Environment is already contaminated.
Begines with a source or evidence of exposure to a contaminant.
