Household chemicals can prove to be deadly.

Developers:

Valarie Rathmell
Methacton School District, Norristown, PA

John Cihiy, Terry Williams
Biocides Research, Rohm and Haas Company

Grade Level:

6 through 10

Discipline:

Biology & Environmental Science

Time Period for laboratory only:

Intermediate Level - one 45 minute class periods
High School - two 60 minute class periods

Goals:

Upon completion of this lesson, the student will:

1. Recognize the possible dangers of household pollutants.
2. Use the scientific method to design an experiment to test chemical pollutants.
3. Measure the effect of various toxic materials on brine shrimp.
4. Measure using scientific units.
5. Operate scientific equipment.
6. Practice basic laboratory safety.
7. Conduct a scientific investigation as a team.
8. Learn about the basic biology of brine shrimp.

Objectives:

Upon completion of this lesson, the student will:

1. Determine the LD50 for a variety of toxic materials.
2. Represent data in chart and graphical form using a computer.
3. Read a dose-response curve to determine toxicity levels of household items.
4. Learn the proper ways to handle and dispose of household pollutants.
5. Operate scientific equipment.
6. Practice basic laboratory safety.
7. Conduct a scientific investigation as a team.
8. Learn about the basic biology of brine shrimp.

Background:

Brine Shrimp

Brine Shrimp (Artemia franciscana) are also known as "Sea Monkeys." These small crustaceans can be found along the California coast, in Mono and Soda Lakes in California and in the Great Salt Lake, Utah. They can be found in salt flats, places where salt water is evaporated commercially to produce salt and are an important food source to many wildlife species, such as flamingos. Brine Shrimp are not found in the open ocean because their only defense mechanism against predators such as fish and other invertebrates is the fact that they can survive in hyper-saline bodies of water. Brine Shrimp can tolerate a salt content of between 25 and 35 percent salt and adults even up to 50 percent. The normal salt content of sea water is between 2.9 to 3.5 percent. Even though this serves as an excellent adaptation in the way of protection from predators it does not give them a competitive advantage when it comes to food. They live almost entirely on the photosynthetic green alga Dunaliella.

	Brine shrimp are only distantly related to the shrimp we eat. The size of an adult brine shrimp is approximately 2 to 4 centimeters. Male brine shrimp are slightly larger than the females. The males have large "arms" located near the head that are called claspers. These are used to hold on to the female during mating.
	The females carry pouches called brood sacks that can produce up to 150 eggs every 3 to 4 days. The eggs hatch within the brood sack and are released into the water as live, swimming baby brine shrimp or nauplii.
	Under the right conditions the nauplii will mature and begin to reproduce within 2 to 3 weeks. Under stressful conditions the eggs will go into diapause and become dormant.

Toxicity

In early civilization, man in his quest for food attempted to eat a variety of materials. Through these experiences, it is likely that man found certain substances to cause illness and even death and others to serve as desirable food for him. This lead to two categories of materials, ones that were poison and others that were food.

In modern day, this concept persists and serves a useful purpose. However, in a strictly scientific sense, this classification is irrelevant. We cannot draw a line between those chemicals that are beneficial and those that are harmful. Rather there are degrees of harmfulness and degrees of safeness for any chemical. Even the most innocuous of substances, when taken into the body in sufficient amounts may lead to undesirable effects. It is therefore plausible to say that the harmfulness and safeness of a chemical is related to the amount of that compound (dose) that is present in the body and how long the body is exposed to that chemical (exposure). It is even true to say that what is toxic to one specimen may not be toxic to another type of specimen.

Toxicology is the study of the quantitative effects of chemicals on biological organisms. A toxicologist focuses not only on the harmful actions of chemicals on organisms but also acquires information on the degree of safeness of the compound. Toxicity is a term used in comparing one chemical with another and always refers to a harmful effect on some biological mechanism. One of the sciences expected to grow in the coming years is environmental toxicology which is concerned with the harmful effects of chemicals encountered by man because they occur in our atmosphere. With the rate of production of industrial and household chemicals, it seems that no one is entirely free of exposure to a variety of chemicals capable of producing undesirable effects on biological organisms.

No matter what our occupation, we handle materials daily that could be potentially toxic. We are often unaware of the degree to which household items could be dangerous. Many household items that we deal with on a regular basis are toxic materials, but we don't usually think of them as being toxic.

Measuring toxicity requires a toxicologist to plot data in the form of a dose-response curve. This curve relates the dose of the chemical to the percentage of animals showing the response (death). This curve will allow you to determine the concentration of a toxic material that causes 50% mortality in a population of test animals. This is called the LD50 (Lethal Dose 50%) test of toxicity. In this experiment the LD50 value for many different household substances have been calculated. Brine shrimp were used as the test organism and only household substances were chosen that may be disposed of by putting them down a drain.

Materials and Equipment:

Samples:

Teacher Preparation:

It is not recommended to use brine shrimp eggs. They tend to be difficult to raise to adult stage. If so allow at least 10 to 14 days before they get to adult stage. It would be best to feed them brine shrimp food that you could get at a pet store. Yeast is not a good option for food. Adult brine shrimp can be kept alive for approximately a week without feeding but aeration must be provided. The animals will also live longer if kept at cool temperatures, (room temperature or lower).

It is recommended for intermediate aged children that the teacher labels and prepares all petri dishes in the morning. Brine shrimp should remain alive. Be careful of water evaporation in the 40 and 50 percent dilutions. Preparation time will take approximately an hour if you are doing 5 classes of 24 students in each.

Safety Precautions:

Students should be required to wear eye protection at all times and there should be an eye wash station in the lab in case students should get any of the household substances in their eyes. If this does occur flush eyes for at least 10 minutes and then seek medical attention.

All substances are found in the typical household and students are readily exposed to them however, aprons and gloves are recommended.
In case of a spill, rinse the area with water.
Students should report any accidental spills and glassware breakage to their teacher.

Procedures:

Intermediate level:

Note this set up is for a class of 24 students with 4 students working at one lab station. The students will work in pairs.

Teacher:

1. Acquire live adult brine shrimp from a local pet store.
2. Place live brine shrimp in a small aquarium tank or a 1000ml beaker with an aerator.
3. Choose 2 samples to work with for the class from the list above.
4. Place 2 petri dishes at each lab table. Three tables will be working on sample A and the other half working on sample B.
5. Label each dish . For example at lab table #1 there would be one dish labeled 5% and one labeled 10% for sample A and at lab table #2 there would be one dish labeled 20% and 30% for sample A and so on for the 40% and 50%. At the other lab tables you would label the dishes for sample B.
6. The setup would appear as below.

	Lab table #1		Lab table #2		Lab table #3
Sample A Dish 1 = 5% Dish 2 = 10%		Sample A Dish 3 = 20% Dish 4 = 30%		Sample A Dish 5 = 40% Dish 6 = 50%
	Lab table #4		Lab table #5		Lab table #6
Sample B Dish 1 = 5% Dish 2 = 10%		Sample B Dish 3 = 20% Dish 4 = 30%		Sample B Dish 5 = 40% Dish 6 = 50%

7. Add the following to each plate:
   5% = 9.5 ml of brine shrimp water + 10 living brine shrimp
   10% = 9 ml of brine shrimp water + 10 living brine shrimp
   20% = 8 ml of brine shrimp water + 10 living brine shrimp
   30% = 7 ml of brine shrimp water + 10 living brine shrimp
   40% = 6 ml of brine shrimp water + 10 living brine shrimp
   50% = 5 ml of brine shrimp water + 10 living brine shrimp

Student:

8. Read lab.
9. Write a 5 sentence introduction. Include information about brine shrimp and toxicity. Also include what you will be testing for in this experiment.
10. Write a hypothesis.
11. Make sure all brine shrimp are living in each petri dish at lab start up.
12. Measure out the following amounts using a graduated cylinder and add the following to the correct plate at the same time:
    5% - .5 ml of Sample A
    10% - 1 ml of Sample A
    20% - 2 ml of Sample A
    30% - 3 ml of Sample A
    40% - 4 ml of Sample A
    50% - 5 ml of Sample A
    Add the same amount of milliliters of sample B into the correct dishes.
13. The teacher should use a stop watch and every 5 minutes the students will record the number of living brine shrimp into individual data table.
14. Upon completion of the time record all class data for both samples A & B on the class data table. This would be best to put on a transparency.
15. Choose one time period and graph data for both samples.
16. Calculate the LD50 value for each sample to determine which sample is the most toxic.
17. Answer discussion laboratory questions and write a conclusion.

Procedures:

High School Level options:

1. Have students figure out dilutions. How many milliliters of brine shrimp water and how many milliliters of sample to add.
2. Have students add the correct amount of shrimp water, shrimp and sample.
3. Have students take data and graph all six samples for all times using a computer.
4. Have students calculate the LD50 value for each sample.
5. Have students discuss which sample is the most toxic and why.

Worksheets:

Worksheets for Toxicity Testing In Brine Shrimp are available for download in PDF format:

•

brine_shrimp.pdf  (24K)

Discussion Questions:

1. What is the difference between a male and female brine shrimp?
2. How do brine shrimp protect themselves?
3. If we had one male and one female within two weeks how many nauplii would we have?
4. What does toxicity mean?
5. What does LD50 mean?
6. How did the behavior of the brine shrimp change immediately after the sample was added? Before death occurred?
7. When comparing your two samples which is more toxic over time?
8. Why is it so important to read labels of household chemicals?
9. Now knowing the effect that some household chemicals have on animals how should you properly handle and dispose of these products?
10. If you were a scientist called in to test the effects of an unknown product how would you do it and what precautions would you take?
11. What different types of information could you find on the internet about brine shrimp?

References:

Brine shrimp company : http://www.brineshrimpdirect.com

Enger, Eldon & Smith, Bradley; Field & Lab Activities in Environmental Science; McGraw Hill Companies, Inc., Dubuque, IA, 1997.

Loomis, Ted A.; Essentials of Toxicology; Lea & Febiger, Philadelphia, PA, 1968.