Doc has the lab and the intructions. it has some math problems too and 4 question at the bottom.
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BCC – ENV11 VIRTUAL LAB – RISK ANALYSIS & HEALTH HAZARDS
In this lab you will:
o Demonstrate how bioaccumulation can lead from small exposures to large exposures through the
o Describe how a dose-response curve helps determine the health effects of environmental pollutants
Estimating Bioaccumulation: DDT in a Lake
A medium sized lake can serve as a major food source for a subsistence community. Suppose that a
community of about 100 people gets much of its protein from fishing on such a lake. Every day, each
person eats one or two fish, which weigh on average about 150 grams. The fish feed primarily on shrimp,
as well as insects and other small animals. You have learned that an algae that is one of the primary food
sources for shrimp in the lake is contaminated with DDT, a persistent organic pesticide that farmers
upstream have begun using to control ants in food crops. You want to know how much of this DDT might
eventually end up in members of the community.
The following shows how to calculate the concentration of DDT in the shrimp, given the concentration in
algae and the eating habits of the shrimp.
This is what we know:
Algae contain about 0.0002 mg of DDT per gram of algae. That is about 0.2 parts per million
Over its (short) life, a shrimp will grow to weigh about 1 gram
The average shrimp eats about 10 grams of contaminated algae during its life.
The amount of DDT consumed by the shrimp can then be calculated:
DDT consumed by shrimp = amount algae consumed × concentration of DDT in algae
DDT consumed by shrimp = 10 galgae × 0.0002 mgDDT per galgae = 0.002 mgDDT
BCC – ENV11 Summer 2020
Since a shrimp weighs 1 gram, the concentration of DDT in the shrimp is
0.002 mgDDT / gshrimp, or about 2 ppm
This assumes that ALL of the DDT consumed by the shrimp stays in its body (a “worst case” assumption
that is probably not true).
Now, use this same method to estimate the eventual concentration of DDT in fish and in humans, given
the following information:
The average fish eats about 1.7 kg of shrimp as it grows to weigh 150 g.
The average person eats 1 – 2 fish per day over a 60-year life.
The average adult weighs about 70 kg.
Note that you will have to compute the total amount of fish eaten by multiplying the amount eaten per day
by the number of days in the individual’s life.
DDT consumed by fish = amount shrimp consumed × concentration of DDT in shrimp
DDT consumed by human = amount fish consumed × concentration of DDT in fish
Continue next page
Creating and Interpreting Dose-Response Curves
Suppose that some mice are fed a chemical called EMBS every day for about two years. They are then
tested for cancer. The results of this test are listed in the table below. Note that animals are usually given
doses based on their body weights, so smaller animals would get relative small total doses, but still the
same in proportion to their weights.
Dose (mg EMBS /
kgmouse body weight / day)
Number of mice
7 / 69
Provide answers to the following questions:
1. Fill in the fourth column, using the example provided as a guide
2. What do these data tell us about the carcinogenic potential of EMBS?
a. Can it cause cancer in mice?
b. Can it cause cancer in humans?
3. Graph the EMBS dose-response curve using excel (Dose X-axis and probability cancer Y-axis)
4. Does EMBS appear to have a threshold for mice? Why?
5. Suppose you fed another group of mice 24 mg EMBS / kgmouse body weight / day. How many would
you expect to get cancer? Why?
6. Suppose you fed yet another group of mice 1 mg EMBS / kgmouse body weight / day. How many would
you expect to get cancer? Why?
9. day. How many would you expect to get cancer? Why?
SUBMIT YOUR WORK IN A PDF OR WORD DOCUMENT TO THE LINK PROVIDED BY
YOUR INSTRUCTOR IN BLACKBOARD
Purchase answer to see full
probability to cause cancer
Dose Response Curves
amount of fish consumed
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