One method 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.
LD50 is defined as the dose that is lethal 50% of the population (ah-ha… LD = Lethal Dose). By analyzing the LD50 for a compound and then comparing it to other known samples, scientists can get a good measurement of how dangerous it would be to the human population.
Question 1
1.
Consider the LD50 graph of Drug X below. To find the LD50 for the compound, draw a horizontal line starting at 50% on the y-axis and ending on the graphed line, then drop a vertical dashed line from that point to the x-axis. Draw. The x-value at this point is the LD50 of Drug X.
What is the LD50 level of Drug X?
Question 2
2.
Question 3
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.
Question 4
4.
Data Analysis
Lethal dose data is shown below for two toxic chemical compounds: arsenic and sodium cyanide. Graph each and determine their LD50 levels.
Question 5
5.
Graph each and determine their LD50 levels. To find the Death rate (%), divide the number of deaths per dose by the total sample size. Then multiply by 100. (EX: for dose 1 [8/190=0.042 X 100 = 4.2%])
Question 6
6.
Graph each and determine their LD50 levels. To find the Death rate (%), divide the number of deaths per dose by the total sample size. Then multiply by 100. (EX: for dose 1 [2/210=0.0095 X 100 = 0.95%])
Question 7
7.
Question 8
8.
Question 9
9.
Question 10
10.
Why is LD50 data so useful in dealing with human health and environmental toxins?
Question 11
11.
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, such as chimpanzees? Explain your opinion.
Question 12
12.
Question 13
13.
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?
More dangerous
Less dangerous
Rank the following compounds in order, starting with the highest LD50 level (top), and ending with the lowest LD50 level bottom: nicotine, sodium chloride, ethanol, sucrose.
Sodium Chloride
Ethanol
Nicotine
Sucrose
At about what minimum dose is the LD50 of sodium cyanide breached?
4 doses
6 doses
8 doses
10 doses
At about what minimum dose is the LD50 of arsenic breached?
8 doses
10 doses
13 doses
16 doses
Which is more dangerous based on the data, assuming that dose size is equal: arsenic, or sodium cyanide?
Equal
Sodium cyandide
Arsenic
LD50 stands for the
Dose (amount) of a chemical that is lethal (deadly) to 100% of the population of a particular species
Dose (amount) of a chemical that is letal (deadly) to 50% of the population of a particular species
Dose (amount) of a chemical that is harmful to 50% of the population of a particular species
Dose (amount) of a chemical that is harmful to 100% of the population of a particular species
A dose reponse curve describes
The effect on an organism or mortality rate in a population based on the dose of a drug or toxin
Dose (amount) of a chemical that is letal (deadly) to 50% of the population of a particular species
The effect on an organism or mortality rate in a population based on the percentage of the organism that dies
The effect on an organism or mortality rate in a population based on the percentage of the organism that gets sick