Going Green as You Clean: Are 'Green' Detergents Less Toxic Than Conventional Detergents?
AbstractThere is strong interest in "going green," including using products that cause less environmental damage when they are disposed of. In this environmental sciences project, you will compare the toxicity of "green" and conventional liquid detergents using worms as test organisms.
Mike M. Pilegard, Student, 2009 California State Science Fair participant
Adapted for Science Buddies by David B. Whyte, PhD.
This science fair project was inspired by the following project from the 2009 California State Science Fair:
Pilegard, M.M. Is It Easy Being Green? Comparing Green and Conventional Cleaners on Environmental Impact, Quality, and Cost.
ObjectiveThe objective of this environmental sciences project is to determine if green detergents are safer for the environment than conventional detergents.
Reduce, reuse, recycle. These are typically known as the three R's of the environment. Every year, Americans throw away billions of containers and other packaging materials that end up in landfills. Reducing the amount of waste you produce is one way to help the environment. Another way to help the environment is to recycle. Many of the things we use every day, like paper bags, soda cans, and milk cartons, are made out of materials that can be recycled. Recycled items are put through a process that makes it possible to create new products out of the materials that come from the old ones.
Reusing is another way to help protect the environment. The idea is simple: instead of throwing things away, try to find ways to use them again. The use of grey water to irrigate plants is an example. Grey water is the water produced by showering, cleaning clothes, washing dishes, etc. It does not include human waste (that is called black water, and is not safe to use for irrigation). Clearly, if grey water is to be used for growing plants, the kinds of detergents used in the house will have to be eco-friendly. In other words, the detergents used should cause little or no environmental damage.
If water is to be successfully reused to irrigate plants, it is critical that the reused water not be harmful to worms and other creatures that are important for the health of the soil. In this environmental science fair project, you will compare the toxicity of "green" (those asserting they are environmentally friendly) and conventional dishwashing detergents by measuring their effects on worms.
Terms and Concepts
- The three R's of the environment: reduce, reuse, recycle
- Grey water
- Black water
- Dilution series
- What are some chemicals that are not found in green detergents?
- What kinds of waste water are considered grey water?
- What does it mean for a chemical to be toxic?
- National Institute of Environmental Health Sciences: Kids' Pages. (2008, October 8). Reduce, Reuse, and Recycle. Retrieved June 30, 2009.
- Wikipedia Contributors. (2009, June 17). Eisenia foetida. Wikipedia: The Free Encyclopedia.. Retrieved June 29, 2009.
Searchable Consumer Product Information Database (cpid) that currently links consumer brands to health effects has been designed to educate consumers about chemical ingredients of household products:
- CPID. (n.d.). Consumer Product Information Database. Retrieved November 9, 2020.
For help creating graphs, try this website:
- National Center for Education Statistics. (n.d.). Create a Graph. Retrieved June 2, 2009.
Materials and Equipment
- Large work area, as you will have many cups out at once
- StyrofoamTM cups, 12-oz. size (84); you will need fewer if you reuse the cups.
- Permanent marker
- Liquid dishwashing detergents (2 "green" and 2 conventional)
- Plastic container (clean and reuse for each detergent)
- Plastic spoons
- 100 mL graduated cylinder, available from Carolina Biological, item #: 721613
- Plastic wrap
- Disposable 5 cc syringe, available from Carolina Biological, item #: 697771. The minimum order size from Carolina Biological is a package of 15 syringes.
Red worms; available from Carolina Biological (item #: 141650), or at any bait store (see the Bibliography, above, for the Wikipedia link, which includes pictures). Other kinds of worms can be substituted, if you choose. You will need 28 worms per detergent.
- Performing the procedure with four detergents, with three trials of each (suggested in order to obtain accurate and repeatable results), you will need a total of 336 worms. The Carolina Biological item contains "about 75 to 100" worms. This means you should order 5 sets of worms to make sure you have enough.
- Potting soil (1 bag)
- Paper towels
- Kitchen scale, metric; available through online suppliers, such as Carolina Biological Supply Company
- Aluminum foil
- Lab notebook
- Graph paper
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Important Notes Before You Begin:
- Because this science fair project involves working with living organisms, namely worms, there will be some natural variability in the starting materials. You will need to be flexible and creative in carrying out the procedure. You should be prepared to adjust the procedure, as needed, to ensure that the results are due to the detergents being tested and not variations in the worm's conditions. Allow time to repeat the procedure for each detergent, for a total of at least three trials.
- The following procedure outlines the steps for a single detergent. Repeat these steps for each detergent you test.
- Control worms are those not exposed to any detergent. The other worms will be exposed to different concentrations of detergent.
- Talk with the worm supplier about the best way to store the worms as you perform the experiment.
Making a Dilution Series of Each Detergent
Label Styrofoam cups with the name of the liquid detergent and the percent concentration, as follows:
- Detergent Name: 0%
- Detergent Name: 3%
- Detergent Name: 6%
- Detergent Name: 12.5%
- Detergent Name: 25%
- Detergent Name: 50%
- Detergent Name: 100%
- It is very important to thoroughly mix the detergent solutions before diluting them in the steps outlined below. Pour one of the detergents into the plastic container and mix it by stirring with a clean plastic spoon. Avoid forming bubbles.
- In the cup labeled 100%, add 100 mL of liquid detergent.
- In the cup labeled 50%, add 100 mL of liquid detergent and 100 mL of water.
- Stir gently, but thoroughly, with the plastic spoon to mix the water and detergent.
- In the cup labeled 25%, add 100 mL of 50% detergent (made in the previous step) and 100 mL of water. Stir to mix.
- In the cup labeled 12.5%, add 100 mL of 25% detergent and 100 mL of water. Stir to mix.
- In the cup labeled 6%, add 100 mL of 12.5% detergent and 100 mL of water. Stir to mix.
- In the cup labeled 3%, add 100 mL of 6% detergent and 100 mL of water. Stir to mix.
- In the cup labeled 0%, add 100 mL of water.
- Cover the cups with plastic wrap to avoid evaporation.
- Repeat steps 1–11 with clean materials to create the dilution series for each detergent.
Exposing the Worms to the Detergents
- Poke several holes with a toothpick in the bottom of seven empty Styrofoam cups.
Label the cups with the name of the detergent, the date, and the percent detergent, as follows:
- Detergent Name, date, 0%
- Detergent Name, date, 3%
- Detergent Name, date, 6%
- Detergent Name, date, 12.5%
- Detergent Name, date, 25%
- Detergent Name, date, 50%
- Detergent Name, date, 100%
- Add 100 grams (g) of potting soil to each cup. Use the kitchen scale to measure 100 g. You might want to put down a piece of paper towel on which to measure.
- Add 5 mL of liquid from the dilution series to the appropriate cup.
- Mix the detergent into the soil with a clean spoon.
- Add four worms to each cup.
Cover the cups with aluminum foil and store them in a cool area, away from direct sunlight or hot air from a heater vent.
- Follow the worm supplier's directions about the best way to store the worms for the duration of the experiment.
- If the room temperature is very hot for part of the day, store the worms in a refrigerator until the room temperature cools off.
- Make sure that the soil stays moist and the temperature does not get too high.
- It might be necessary to keep the worms in the refrigerator for the entire duration of the experiment. (Check with your family before putting the worms in the refrigerator.)
- Repeat steps 1–7 for each of the three additional detergents. You should have 28 cups with worms in them when this section is completed (seven for each of the four detergents).
- You can either empty and discard the cups full of the dilution series, carefully and thoroughly wash them out to reuse for your second and third trials, or store them in a safe place to reuse for your second and third trials.
Analyzing the Effects of the Detergents on the Worms
- After five days, pour the contents of the cups, one at a time, onto a surface covered with newspaper. Make sure to keep track of the detergent and dilution for each batch of worms.
- Record how many worms are alive or dead for each detergent and dilution in your lab notebook.
Graph your results. Put the strength of the detergent on the x-axis, in percent, and the number of dead worms on the y-axis.
- Note: All of the control worms should be alive. If they are not, you may need to shorten the period of exposure, or try alternative soils.
- Compare the "green" detergents with the conventional detergents. Are "green" detergents better for the environment than conventional detergents?
- Repeat the entire procedure so that you have at least three trials for each detergent. You can reuse the set of dilutions that you made in the first step in different trials. Remix each one a little before reusing; be sure to use a different plastic spoon for each detergent. Repeating the procedure ensures that your results are accurate and repeatable.
Ask an Expert
- Vary the concentrations and times of exposure to collect additional data.
- Determine the dose that kills 50 percent of the worms. This is referred to as the LD50 (stands for lethal dose for 50 percent of a population). You will need more worms per dose.
- Instead of just looking at "alive" vs. "dead" worms, devise a scale for measuring the effect of the detergent on the worm's activity level. For example: 1) Same level of activity as untreated worms; 2) Low level of activity; 3) Very low level of activity. Graph your results.
- Test the ability of the detergents to block seed germination. See the Science Buddies project How Do Roots Grow When the Direction of Gravity Changes? for a procedure about germinating seeds. Use the detergent dilutions made in the procedure above.
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