Name: ________________________ Period: _________________ Date: __________________
Creating LD50 Graphs for Different Substances
Background
One of the methods that scientists can use to determine the toxicity of a chemical compound is an LD50 test.
This test involves introducing different dose levels of the compound to be tested to a group of experimental
subjects. The most commonly used experimental subject is lab rats or mice, because they have many
physiologic similarities to humans.
Dose response curves usually look like this:
LD50 is defined as the lethal dose to 50% of the population. By analyzing the LD50 for a compound and
comparing it to other known samples, scientists can get a good measurement of how dangerous it would be to
the human population.
1. Consider the LD50 graph of Drug X above. Draw a vertical dashed line starting at 10mg/kg on the xaxis and ending on the graphed line. Draw a horizontal line starting at 50% on the y-axis and ending on
the graphed line. This is the LD50 of Drug X.
2. What is the LD50 level of Drug X?
3. A different drug is tested and found to have an LD50 level of 5mg/kg. Would you consider this drug to
be more or less dangerous than Drug X? Explain.
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4. Rank the following compounds from 1-4, starting with the highest LD50 level, and ending with the
lowest LD50 level.
Nicotine _____
Written by James Dauray
Alcohol _____
Sodium Chloride _____
(Table Salt)
Sucrose _____
(Table Sugar)
http://www.docstoc.com/profile/jamesdauray
Page 1
Data Analysis
Lethal dose data is shown below for two toxic chemical compounds: arsenic and sodium cyanide. Graph each
and determine their LD50 levels.
Sodium Cyanide
Dose
Number
of Deaths
1
8
2
16
3
30
4
48
5
68
6
89
7
119
8
140
9
173
10
190
Arsenic
( Sample size = 190 )
Death
Rate
(%)
( Sample size = 210 )
Dose
Number
of Deaths
2
2
4
6
6
11
8
22
10
41
12
72
14
131
16
198
18
210
Death
Rate
(%)
5. What is the LD50 of sodium cyanide?
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6. What is the LD50 of arsenic?
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7. Which is more dangerous based on the data, arsenic, or sodium cyanide?
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Conclusion
8. Why is LD50 data so useful in dealing with human health and environmental toxins?
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9. In the course of measuring this data, many thousands of lab mice and rats have been killed. Do you
consider this to be ethical research? Why is data collected on lab mice instead of humans? Would it be
more ethical to use a species that is more closely related to us like chimpanzees? Explain your opinion.
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Further Research
This is a table showing the LD50 of several substances, both toxic and non-toxic. For each substance, calculate
the amount of each substance that statistically would have a 50% chance of killing you.
1. Record your weight in pounds here: __________________
2. Convert your weight to kilograms by multiplying by 0.45: _________________
3. Calculate your human lethal dose by multiplying your mass in kilograms by the LD50, then dividing by
1000 to convert to grams.
Substance
LD50 (mg/kg)
Sucrose
29,700
Ethanol
7,060
Sodium chloride
(table salt)
3,000
THC (found in
cannabis)
1,270 (males)
730(females)
Aspirin
200
Caffeine
192
Nicotine
50
Arsenic
14
Sodium cyanide
6.4
Venom of the
Australian Inland
Taipan snake
0.025
VX Nerve Gas
0.0023
Batrachotoxin
(from Poison Dart
frogs)
Polonium-210
(nuclear fission
waste product)
0.0020
0.00001
Lethal Human Dose (grams)
= mass x LD50 / 1000