ENV 8243 Creating LD50 Graphs for Different Substances

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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. _____________________________________________________________________________ More dangerous because the LD50 of Drug X is higher than the different drug. It

would take less of the different drug to kill someone, making it more lethal

_____________________________________________________________________________ _____________________________________________________________________________ 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 _____ (Table Salt)

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Sucrose _____ (Table Sugar)

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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 (%)

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5. What is the LD50 of sodium cyanide? _____________________________________________________________________________ 6. What is the LD50 of arsenic? _____________________________________________________________________________ 7. Which is more dangerous based on the data, arsenic, or sodium cyanide? _____________________________________________________________________________

Conclusion

8. Why is LD50 data so useful in dealing with human health and environmental toxins? _____________________________________________________________________________ We can see how much humans can have without dying which is helpful when the

environment is exposed to a toxin

_____________________________________________________________________________ _____________________________________________________________________________ 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.

I consider testing on rats and mice ethical because we need a way to find out the toxicity of _____________________________________________________________________________ substances without testing on humans. It would less ethical to test on chimpanzees because _____________________________________________________________________________ they are more conscious and similar to humans _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________

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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)

Lethal Human Dose (grams) = mass x LD50 / 1000

0.0020 0.00001

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