Take a stab at answering every question. Show all your calculations. If you leave a blank, I can’t give you any credit at all.

  1. (20 points) What are the advantages and disadvantages of animal studies and epidemiological studies for establishing dose-response relationships?
  1. (20 points) Underline the correct answer to each of the following:
  1. The 95% confidence interval

(a) Has more outliers than the 99% confidence interval

(b) Has fewer outliers than the 99% confidence interval

(c) Has the same number of outliers as the 99% confidence interval

B The dose for an incremental lifetime cancer risk of 10-6

(a)  Increases as the estimated cancer slope factor increases

(b)  Decreases as the estimated cancer slope factor increases

(c)  Is independent of the value of the cancer slope factor

C For two normal distributions with the same mean, but different standard deviations, the 95% confidence interval will be:

(a) The same for both distributions

(b) Larger for the distribution with the smaller standard deviation

(c) Smaller for the distribution with the smaller standard deviation

D. Equal concentrations of heptachlor, a known human carcinogen, are found at two different sites.

(a)  The incremental risk is the same at the two sites

(b)  The incremental risk is different at the two sites

(c)  The incremental risk at the two sites might be the same or it might be different.

3.  (20 points) Go to the EPA IRIS data base at http://www.epa.gov/iris/index.html Click on List of IRIS Substances. Select Heptachlor (the IRIS Summary). Answer the following questions in your own words:

  1. What is meant by oral reference dose?
  2. What types of studies did the EPA use to estimate the oral reference dose? (human, animal, or both?)
  3. What were the adverse effects upon which the Agency based its estimate?
  4. What is the risk of cancer for a person who ingests the oral reference dose every day for 70 years? Do you think it would be advisable to do so?

For definitions of terms you do not understand, click on IRIS Glossary on the front page.

4.(20 points) The article below appeared in the Washington Post a little over a month ago.

a. What reason does the article give for not eating the fish?
b. What additional data would you need to assess the risk?

The Washington Post

For your own safety, please do not eat these fish from the Potomac

ByPerry SteinFebruary 11, 2016


If you’re in search ofsome locally sourced fish, be selective about what you choose to consume from the Potomac River.

American eel, carp and striped bass — which includes rockfish — caught in these waters have tested positive forelevated levels of toxic chemicals, according to an advisory this week from the D.C.Department of Energy and Environment. Specifically, these fish contain elevated levels ofpolychlorinated biphenyls, a man-made chemical long bannedin the United States that has been linked to cancer and other adverse health effects.

“Our goal is to protect the health and well-being of our residents,” the agency’s director,Tommy Wells, said in a statement. “This advisory helps ensure that residents who enjoy fish from District waters are aware of the health risks associated with consuming certain fish species.”

The advisory also suggests eating certain fish caught in city waters — sunfish, blue catfish, northern snakehead, white perch, largemouth bass, brown bullhead catfish and channel catfish — on a limited basis.

The city’senvironmental agency has been monitoring contaminationlevels since 1980 and notes that improvements have been made along the way.

5.(20 points) David Hassenzahl discusses the relative risks of eating peanut butter contaminated with aflatoxin and apple juice contaminated with UDMH, a degradation product of Alar, in the Power Point presentation in the Week Four, Module 4 Conference. The following Table shows his input data.

Variable / Units / Average / 5th %ile / 95th %ile / Distribution
Peanut butter intake / g/day / 11.38 / 2.00 / 31.86 / Lognormal
Apple juice intake / g/day / 136.84 / 16.02 / 430.02 / Lognormal
Aflatoxin concentration / ug/kg / 2.82 / 1.00 / 6.5 / Lognormal
UDMH concentration / ug/kg / 13.75 / 0.5 / 42.00 / Lognormal
Aflatoxin potency / kg-day/mg / 17.5 / 4.02 / 28.33 / Normal
UDMH potency / kg-day/mg / 0.49 / 0.00 / 0.85 / Normal
  1. Calculate the daily cancer risk for a child who weighs 20 kg and who eats an average amount of peanut butter
  2. Do the same for a 20 kg child who drinks an average amount of apple juice.

NOTE: Daily cancer risk = Intake x Concentration x Potency / Body Weight

  1. Calculate the maximum daily cancer risks for peanut butter and apple juice based on the 95th percentiles.
  2. Run 10,000 Monte Carlo simulations with Crystal Ball using the spreadsheet below and answer the following questions based on the results of your run.

PB and AJ.xls

(NOTE: Download the spreadsheet to your hard drive. Open Crystal Ball.. Click on Open Workbook, and click on the saved spreadsheet.)

  1. What is the median daily cancer risk for peanut butter contaminated with aflatoxin and for apple juice contaminated with UDMH? (Refer to the percentile charts)
  2. What is the probability that the risks are less than the conservative values you calculated in c.?
  3. What is the probability that the risks are greater than the average values you calculated in a. and b.?
  4. What is the probability that the risks are greater than 1E-6 and less than 1E-4?
  5. Which are the most sensitive variables for the peanut butter calculations and the apple juice calculations?
  1. Discuss your results briefly.