This set of Hazardous Waste Management Multiple Choice Questions & Answers (MCQs) focuses on “Risk Management – Uncertainty Analysis”.
1. A discussion of uncertainty is critical for _____________
a) Characterization of risk
b) Chemical analysis
c) Pathway analysis
d) Data calculation
Explanation: A discussion of uncertainty is critical to the full characterization of risk, because it provides a better understanding of the implications and limitations of the risk assessment (EPA 1991a).
2. ________ is a valuable tool for prioritizing the contaminants.
a) Chemical analysis
b) Pathway analysis
c) Uncertainty analysis
d) Site analysis
Explanation: Uncertainty analysis is a valuable tool for prioritizing the contaminants and exposure pathways of concern to guide the acquisition of additional data to reduce uncertainty in risk predictions.
3. What is the formula to calculate Hazard Index (HI)?
a) HI = (C*I*ED*EF) / (BM*AT*RfD)
b) HI = (C*I*EF) / (BM*AT*RfD)
c) HI = (C*I*ED*EF) / (BM*AT)
d) HI = (C*I*ED) / (BM)
C = concentration of the chemical in the contaminated medium
I = estimated intake rate of the contaminant
ED = exposure duration
EF = exposure frequency
BM = body mass
AT = averaging time
RfD = reference dose for the chemical of interest
If the HI is below 1, it is highly unlikely that exposure to the chemical would lead to an adverse health effect. If the HI is greater than unity (LO), remediation may be warranted.
4. A quantitative uncertainty analysis requires knowledge about the ___________
d) Potential range of values likely to encompass the true but unknown value
Explanation: A quantitative uncertainty analysis requires knowledge about the potential range of values likely to encompass the true but unknown value for each parameter used in the equations employed for a reasonable estimate of the risk to a maximally exposed individual.
5. To evaluate the magnitude of uncertainty about a risk estimate ______ procedure should be utilized.
a) Statistical error propagation
b) Mathematical error propagation
c) Geographical error propagation
d) Scientific error propagation
Explanation: Statistical error propagation procedures also provide the most appropriate means for prioritizing and ranking the assumptions and model subcomponents that dominate the uncertainty in the risk estimate.
6. What is the first step under parameter uncertainty analysis?
a) Specify the maximum conceivable range of potential values relevant for unknown parameters with respect to the endpoint
b) Specify a subjective probability distribution (pdf) for values occurring within this range
c) Account for dependencies and/or correlations among parameters
d) List all uncertain parameters
Explanation: To perform parameter uncertainty analysis, the first step according to (IAEA 1989) is to list all uncertain parameters (include additional parameters to represent uncertainty in model structure).
7. Uncertainty in the point estimate that is less than one order of magnitude is considered ___________
d) Very high
Explanation: Uncertainty in the point estimate that is less than one order of magnitude is considered low, uncertainty in the point estimate greater than that of one order of magnitude but less than two orders of magnitude is considered moderate, and uncertainty that is more than that of two orders of magnitude is considered high according to EPA, 1989.
8. An uncertainty analysis is additionally useful to weigh the benefits against the _____________
a) Costs of alternative remedial actions
b) Chemical plans
c) Exposure plans
d) Toxicity actions
Explanation: Performing quantitative analysis of uncertainty using analytical or numerical methods to obtain uncertainty in the components of the risk assessment equations into an evaluation of uncertainty in the overall result reduces cost for remedial actions.
9. If the cost of remediation required to reduce exposure or risk is low, a quantitative uncertainty analysis is not required.
Explanation: For small contaminated sites with inexpensive remediation options, it is sensible to clean up the property than to undertake a detailed risk analysis and its attendant uncertainty.
10. If screening calculations indicate that the risk is below risk levels of concern, a quantitative uncertainty analysis may not be necessary for site.
Explanation: Detailed analyses will indicate the true risk is even less than initially estimated because screening calculations are designed to provide a risk estimate that is highly improbable to underestimate the true risk.
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