As a biology teacher, I hope you’re aware of, and deeply disturbed by, the enormous volume of plastics that we all discard, day after day. We can see cups, bags, and other plastic trash by the roadside and in waterways, and it’s not hard to envision what happens when fish or turtles eat bits of this garbage or get tangled up in it.
It’s one thing to be alarmed about the amount of trash we see as we walk, ride, or drive by. It’s quite another to understand that the plastics problem extends down to the microscopic scale as well. The big pieces we see physically break down into smaller and smaller pieces. But did you know that cosmetics and fibers from clothing contribute plastic to water, too? These bits of plastic start small and stay small. Microplastics are hard to see with the naked eye, but they climb the food chain just the same.
Recently, The American Biology Teacher published a couple of papers by Franz X. Bogner and his team in Germany (see references below). Taken together, the two papers are excellent because they explain how we release plastics to the environment, why plastics persist when other types of pollutants do not, the environmental consequences of the plastics, what to look for in lists of product ingredients, and ways to minimize the use of plastic. The activities are targeted to an elementary school level, but they could easily be adapted to use in the college classroom.
The most memorable thing that I learned from the papers is that it is extremely easy to extract microplastics and view them with supplies no more sophisticated than water, a coffee filter, a funnel, and a cell phone camera. For example, in the first photo, you can see the microplastic beads that I filtered from a droplet of Walgreens Deep-Acting Exfoliating Scrub. All I did to create this photo was to mix a drop of the facial scrub in about 30 milliliters of water and pour it through a coffee filter placed in a funnel over a beaker. Once the water had passed through the filter, I cut the filter open and laid it on a dissecting microscope stage for photography. It’s easy to compare the size of the white and purple microbeads to the 1-mm markings on the ruler.
The second photo shows the microplastic fibers from a small piece of black flannel. To release these fibers, I cut a small square of the flannel (about a square inch) and swished it in about 30 milliliters of water containing a bit of dishwashing detergent. As before, I poured the mixture though a coffee filter in a funnel over an empty beaker. In this case, we used a cell phone camera instead of the dissecting scope to see if the microscope was even necessary to visualize the fibers and estimate their size. As you can see, the cell phone camera did a fine job on its own.
As biology instructors, what can we do with this simple activity? You could follow the Bogner team’s example and have students learn to find and visualize microplastics in everyday consumer items. (You can also use the workbooks and other materials they provide to do their full set of activities if you choose.) If you’re looking for something simpler, though, here are a few ideas.
First, it is easy for students to understand how the microplastics from facial scrub and laundered fabrics make their way into the water supply. From there, they could use their ecology skills to propose food chains or food webs that explain why microplastics accumulate in tissues of animals at the highest trophic levels.
Second, if you’re teaching about the tools of science, students can use photos like these as part of an exercise in learning to use the microscope and/or learn metric units of length.
Third, perhaps you’d like your students to interpret graphs from the scientific literature. Data from a paper can seem pretty abstract, especially to a beginner. Perhaps seeing examples of microplastics can help your students connect the professional world of published science to something they can see with their own eyes.
Finally, my colleague recently included microplastics in a short, asynchronous lesson called “Plastic Pollution” for his nonmajors biology course. The lesson contains online videos and assessment ideas. If you’d like to see it, please leave a comment below and we’ll be glad to email it to you.
Baierl, Tessa-Marie and Bogner, Franz X. 2021. Plastic Pollution: Learning Activities from Production to Disposal – From Where Do Plastics Come & Where Do They Go? The American Biology Teacher 83 (5): 320–324.
Raab, Patricia and Bogner, Franz X. 2020. Microplastics in the Environment: Raising Awareness in Primary Education. The American Biology Teacher 82 (7): 478–487.