FINAL EXAM

OPEN BOOK
 
 

ENVH/PBAF/CEWA 577

Risk Assessment for Environmental Health Hazards

Faustman/Omenn
 
 

December 1996






This exam has 5 pages. Be sure your exam is complete before starting. Please write all answers in the blue book. Answers written on the exam itself will not be considered in grading. The exam is organized into two main parts - short answ er and essay/calculation. In the essay/calculation section, the questions are broken up into several different areas of risk assessment. Points for each question are indicated in parentheses. There are a total of 100 points on this exam.
 
 

Please read all sections carefully. Most sections will give you a choice of questions to answer. Indicate on your exam what section and question you are answering.
 
 

PART I. Short Answer
 
 

Answer 6 of the 9 questions given below (4 points each). Your answers should not exceed 1/2 page per question. Please include the question number along with your answer.
 
 

1. What is a bioconcentration factor (BCF) and what is it used for? What are its limitations?

2. What is a Toxicity Equivalency Factor (TEF) and how is it used? What are its limitations?

3. What are the two main types of epidemiological studies? What are the advantages and disadvantages of using epidemiological studies in risk assessment?

4. Provide at least two advantages and two disadvantages of using a chronic bioassay for carcinogenicity.

5. Identify two short term assays and give 2 advantages OR 2 disadvantages of using these types of tests.

6. Describe the concept of a "Bright Line" and give at least two examples.
 
 

7. Describe the EPA Carcinogen Classification System (i.e., A, B1, B2, etc.) and the type of evidence required for each category. Given that benzene has been shown to cause leukemia in several human epidemiological studies and one rodent bioassay, what would the classification for benzene be?

8. List at least two parameters used to evaluate ecological health risk. How might evaluating ecological risk conflict with evaluating human health risks (List two possible conflicts)?

9. Social/cultural impacts are frequently ignored in the standard risk assessment process. Do you think it is important to include these assessments in government decision making? Why or why not? Provide an example with your answer.
 
 

 PART II. Short Essay/Calculation
 
 

Section A. Risk Communication (Everyone must answer this question)
 
 

1. Identify the four different philosophical approaches to evaluating safety and briefly discuss how they differ. (10 points)
  Section B. Dose Response Assessment (Please answer two of the next four questions in Part II Section B. Each question is worth 10 points.)
 
 

1. Using the following data from a study of the reproductive toxicity of codeine in rodents (Williams et al. 1991), identify a NOAEL for use in a risk assessment. Give the basis for why you chose a particular value (10 pts).
Mice dosed with Codeine
0 37.5 75 150 300 Dose mg/kg
11 11 10.8 11 11 No. live fetuses per litter
1. 0.96 0.99 0.88 0.75 avg. body wt per litter
0.4 0.0 0.6 0.6 1.2* Fetuses malformed per litter (avg)
4 0 15* 26* 32* Litters with malformations
 

* = statistically different from controls, p=0.05
 
 
 
 
 

2. On the following dose-response curve, identify the 10 percent response level dose (i.e., the dose which yields a 10 percent response). Do this for both the MLE and the 95% confidence interval. (10 points)
 
 
 
 

4. What are the advantages of using the Benchmark dose approach over the NOAEL/LOAEL approach? Discuss at least two points. (10 points)
 
 

Section C. Exposure Assessment (Answer questions 1, and 2a and 2b in Section C)
 
 

1. You are a risk assessor working for EPA Region X and have been asked to look at the risks posed by a leaking municipal waste dump. The dump was created in the 1930âs and lies right along the shore of the Columbia River. There are families livin g less than one mile away. Although there are hundreds of chemicals leaking from this dump, the primary chemicals of concern are polychlorinated biphenyls (PCBs) and chromium, both of which are known to be hazardous to human and ecological health. These chemicals are known to be present in soil on top of the dump as well as in groundwater and surface water in the Columbia River. Discuss the potential exposure pathways that might be important for this site. Your boss has asked you to be very thorough and consider all the possible targets for these chemicals, both human and animal. Hint: A good way to do this is to sketch out the pathway from the contaminated media to the particular target (human or animal). (6 points)
 
 

2. The town in which you live is contaminated with a particularly nasty chemical, yulinol, which was discharged over many years by the townâs only industry, the Rainy State Christmas Tree Company. An exhaustive study by State officials has shown th at the average concentrations of this chemical in environmental media are as follows: 450 mg/kg in soil, 10 mg/l in groundwater and 0.002 mg/m3 in air. A quick search of EPA databases revealed that yulinol is not carcinogenic but has some adverse health effects. The reference dose (RfD) for this chemical is 1.5x10-1 mg/kg/day. Please answer each of the following parts of this question. (12 points total)
 
 

a. Assuming drinking water ingestion is the only important route of exposure, calculate the lifetime average daily dose (LADD) for local adult residents via this pathway. You also believe that only 50% of yulinol is absorbed in the GI tract. You m ay use either upper bound or central tendency estimates of exposure factors, but be sure to indicate which you use. (6 points)
 
 

b. Calculate the noncarcinogenic risk for the adult residents, using the LADD calculated above. Is there a problem? (6 points)
 
 
 
 

 Section D. Group Project
 
 

1. Uncertainty (Answer 1a or 1b)
 
 

a. Identify at least four major sources of uncertainty in your groupâs risk assessment and how they might have affected your overall conclusion. (8 points)
 
 

b. Choose one case study done by another group. Compare and contrast the four major sources of uncertainty in that case with those from your group project. (8 points)
 
 
 
 

 2. Prioritization (All students should answer this question. Use no more than 2 pages front and back.)
 
 

Choose two studies done by other groups. Describe how you would prioritize these two case studies compared with your case study for timeliness of action and for use of federal dollars. In answering these questions, identify four criteria that you use for ranking the three case studies. (20 points)
 
 

BEFORE LEAVING, PLEASE COMPLETE THE COURSE EVALUATION FORMS.
 
 

We value your opinions and comments. Thank you for your participation in the class. We hope you have enjoyed it, gained some valuable information, and will find the material useful in your professional endeavors.
 
 

Best wishes for the Holiday Season and the New Year!