I recently read The Omnivore’s Dilemma by Michael Pollan. One of the issues Pollan calls readers’ attention to is the meaning of “organic.” The U.S. Department of Agriculture appears to have a clear sense of what it means to be organic. See their web page on which 12 links to organic farming-related documents appear. Most consumers believe organic farming means no drugs or chemicals have been allowed to contact the animal or plant destined for the market. But Pollan argues that due to the pervasive use of pesticides, herbicides, and hormones, combined with the tendency to highly process foods, it is nearly impossible to bring “organic” food to market.

Even if a farmer avoids intentionally adding chemicals and drugs, they are so well entrenched in the environment that, due to ecological relationships, agricultural products cannot avoid them. Pollan further calls for transparency not only in what chemicals the food was grown with but also in the ways it is processed.

Speaking of transparency, the NYTimes.com recently published an interview with an Environmental Protection Agency (EPA) engineer who certifies household cleaning products as “green,” another ubiquitous, yet amorphous buzzword. In the interview, Clive Davies explains that if a manufacturer’s ingredients list is free from chemicals considered particularly harmful to the environment, it gets the EPA’s seal of approval. The EPA does not have a list of products that do not meet the standards, nor can the agency feasibly verify the submitted ingredient list.

How to Turn This News Event into an Inquiry-Based, Standards-Related Science Lesson

Discussion of the meaning of terms such as “organic” and “green,” “soap” and “detergent,” their ingredients, and impact on the environment is connected to the Science in Personal and Social Perspectives, Scientific Inquiry and Life Science content standards of the National Science Education Standards.

Ask students if they use soaps and detergents at home. What is the difference between a soap and a detergent? According to Kiwi Web: Chemistry and New Zealand, detergent is the evolutionary descendant of soap. That is, soap is plant-based and renewable and has been in use for thousands of years. In the early 1900s when soap was synthetically mass produced, largely from petrochemicals, it became a detergent.

Both soap and detergent are considered surfactants, which is a blended word for surface-active agent. The role of surfactants in detergents is to surround nonpolar substances like fats and oils and confer some polarity on them, so that water, a polar substance, can then adhere to the substances and wash them away.

What are these detergents made of? Many contain phosphate, though not as much as in the past. Phosphorus is a needed nutrient by all living things to build nucleic acids and ATP. Phosphorus usually is available in limited quantities in nature, and therefore limits population growth. Ask students where the detergents go after use. Down the drain and into the environment. What effect does the addition of phosphorous have on aquatic ecosystems? Algal blooms, which block light, increase the acidity of the water through production of CO₂ and carbonic acid, die, and decompose. This increases the bacteria/decomposer populations that consume available oxygen in respiration. This in turn negatively impacts almost all other species living in or near the area.

What is the effect of introducing surfactants to the environment? According to Davies, surfactants can stick to a fish’s gills and interfere with its ability to obtain oxygen through diffusion from the water. As you might imagine, surfactants can cause a negative ripple effect in the community.

What’s a “green” detergent? How would you know? Share the NYTimes.com story with the students. Allow them to critique it. What are the weaknesses in the story? What is not being said? Share a couple of reader responses with them, accessed by clicking on the link on the left side of the story page.

Consider having students conduct the suggested experiment — where they use progressively less laundry detergent and observe the effects. You could brainstorm variations such as a similar application to use of dishwasher detergent and shampoo.

Students can increase their scientific inquiry skills while learning some valuable consumer-related lessons.

The following are some related resources from the National Science Digital Library Middle School Portal: Chemistry: Making it Real; Stream Ecology; and SDA Kids Corner.

We Need Your Help

We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? Do you have a favorite activity that you would like to share? We invite you to share with us and other readers by posting your comments. Please check back each week for our newest post or download the RSS feed for this blog. You can also request email notification when new content is posted (see right navigation bar).

Let us know what you think and tell us how we can serve you better. We want your feedback on all of the NSDL Middle School Portal science publications. Email us at msp@msteacher.org