1. LD50 in a toxicity test stands for ______
a) a dose that will kill 50% of an exposed population
b) a dose that would not affect or harm 50% of an exposed population
c) a dose that will kill 25% of an exposed population
d) a dose that would not kill 25% of an exposed population
Explanation: The value of LD50 for a substance is the dose required to kill half the participant of a tested population after a specified test duration and it also depends on the rate of exposure.
2. What is the main objective of risk characterisation?
a) Estimation of the potential for adverse health or ecological effects to occur from exposure to a stressor
b) Determination of pathways
c) Estimation of exposure
d) Collection of data
Explanation: Risk characterization is the qualitative and quantitative determination of combined risks to receptors from individual chemicals of concern and exposure pathways, and the associated uncertainties
3. If the MDD from the target population is smaller than the RfD, the exposure is considered relatively _________
a) Safe
b) Unsafe
c) Permissible
d) Accident
Explanation: permissible exposure is defined in the dose-response phase of the risk assessment, comparison with the maximum daily dose (MDD) occurring within the tested population. If MDD is less than RfD it is considered safe.
4. If the MDD from the target population is greater than the RfD, the exposure is considered relatively ________
a) Safe
b) Permissible
c) Unsafe
d) Void
Explanation: If MDD is higher than the RfD and if is approaching within 100 fold of the NOEL according to the toxic studies, then the exposure is considered unsafe.
5. What should be the MOE after extrapolation to humans to be considered as a low risk
a) Over 20
b) Over 30
c) Over 40
d) Over 10
Explanation: The Risk of exposure for non-oncogenic effects is expressed as a Margin of Exposure (MOE). If it’s over 10, No Effects Level is a lot higher than the actual exposure occurring among the most exposed individuals within the target population
6. Which of the following is not a component of risk characterisation?
a) Study of exposure duration, frequency, and magnitude
b) Study of pathways and receptors
c) Study of toxicity values
d) Chemical analysis
Explanation: The components of risk characterization focus on gather, review, compare, and organize the outputs of the exposure and toxicity assessment.
7. The sum of risk of each individual chemical is _________.
a) Total pathway risk
b) Simple pathway risk
c) Negative pathway risk
d) Complex pathway risk
Explanation: Total pathway risk is the determination cumulative risk of each exposure pathway by adding risk from each individual chemical in that pathway.
8. What is the final stage of risk assessment?
a) Hazard identification
b) Risk characterisation
c) Exposure assessment
d) Toxicity assessment
Explanation: The final stage of risk assessment is to calculate risks. Risks consists of calculating quantitative estimates of carcinogenic and non-carcinogenic risks to receptors.
9. Which of the following does not come under elements of risk characterisation?
a) Qualitative description of uncertainty
b) Presentation of the risk estimate
c) Communication of the results of risk analysis
d) Chemical analysis
Explanation: Analysis of chemicals does not belongs to risk characterization. Generation of a quantitative estimate of risk is the first step to be considered.
10. _________ document provides guidance to EPA and other government employees for clean-up of hazardous site.
a) Superfund Risk-Assessment Guidance
b) RCRA Risk-Assessment Guidance
c) NPL Risk-Assessment Guidance
d) HRS Risk-Assessment Guidance
Explanation: The Superfund document provides guidance to EPA and other government employees and contractors who might be risk-assessment reviewers, risk assessor, remedial project managers, or risk managers involved in clean-up of superfund-site.