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 x-axis 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 _____ Alcohol _____ Sodium Chloride _____ Sucrose _____
(Table Salt) (Table Sugar)
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 ( Sample size = 190 )
Dose / Number of Deaths / Death Rate (%)1 / 8
2 / 16
3 / 30
4 / 48
5 / 68
6 / 89
7 / 119
8 / 140
9 / 173
10 / 190
/
Arsenic ( Sample size = 210 )
Dose / Number of Deaths / Death Rate (%)2 / 2
4 / 6
6 / 11
8 / 22
10 / 41
12 / 72
14 / 131
16 / 198
18 / 210
/
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) / Lethal Human Dose (grams)= mass x LD50 / 1000
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) / 0.0020
Polonium-210 (nuclear fission waste product) / 0.00001