Activity - Acute Toxicity: LD50 by the Numbers

Skills: Observation, Biology, Scientific Method, Discussion, Presentation
Activity - Acute Toxicity: LD50 by the Numbers - Articles

Updated: November 13, 2017

Introduction:

Many people are not aware of the potential harmful effects of household chemicals and pesticides. Toxicity is the ability of a chemical to cause injury or death. This activity allows students to quantitatively measure the toxic effects of common household chemicals and/or pesticides on brine shrimp (sea monkeys). Students will dose a group of brine shrimp with specific amounts of test chemicals and notice how the chemicals affect their ability to swim. At some point, enough chemical will be added that some of the shrimp are killed. LD50 is the term for "lethal dose at which 50% of the animals die". This measurement is used by the Environmental Protection Agency to measure the acute toxicity pesticides, that is, how much in a single dose will cause injury or death. A small number for the LD50 means a small amount of the chemical is acutely toxic. In this experiment, students will be able to compare the relative toxicity of chemicals chosen by observing the relationship of dose to effect on the shrimp.

Learning Objectives:

1. Learn that everyday household chemicals can adversely affect the environment.
2. Learn to make observations about a living organism.
3. Understand the idea of conservation when using chemicals.
5. Learn decision-making skills needed in pest management decisions.

Materials Needed:

  • Brine Shrimp (available from most pet stores or can be cultivated from dry eggs)
  • Handouts
  • Petri Dishes
  • Plastic Pipets
  • Bathroom Cleaners (4 with one being environmentally friendly)
  • Waste Container
Timeline:
One full class period.

Procedures:

Teacher: Read background material in this manual on chemical use and acute toxicity.

1. Present your choice of background information on chemicals & chemical issues.
Discuss and answer student questions. Review steps and tactics of IPM.

2. Have students make observations about animals they are familiar with. Ask them to describe how a fish swims or a dog runs. Tell them they will need to make these observations on brine shrimp when doing this exercise.

3. Ask students "Have you ever cleaned your bathroom?" then lead them in a discussion about what they use to clean and what the bathroom smells like right after using the cleaners. Have the students talk about how being around the cleaners for too long makes them feel.

4. Group students into groups of 4 or 5 and show students some common bathroom cleaners, (pick one environmentally friendly cleaner to be part of the group) and tell them that they will be testing these cleaners' toxicity on brine shrimp.

5. In each group have students place ten brine shrimp in each of 5 petri dishes using a pipet to transfer the shrimp.

6. Have students make observations about how the shrimp are moving in the petri dish.

7. Have students place a few drops or sprays of each cleaner in 4 of the petri dishes, use a different cleaner for each dish. Do not add any cleaner to the 5th dish.

8. During the exercise, have groups write and draw how the chemicals affect how the shrimp swim. Have each group pick a cleaner that they would use in their home and explain why.

9. Bring all the students back together in one group. Have each group present which cleaner they chose and explain why.

10. Talk to the students about dangers of chemicals in the household and what this exercise taught them about their use in their home.

Other

For older students a graphing exercise dealing with LD50 for each cleaner can be added. For students in grades 11-12 an exercise describing the affinity for chemical in biological tissue can be performed to help explain the why some chemicals affect animals and others do not.

Resources

For more contacts for information about the toxicity of chemicals, see references in the pesticide overview section.