The Life & Deaths of a Toothbrush (Part 1)
Post by Sebastian Carpenter, CeCe Liu, Joe Nangle & Ji Young Ohn for Prof. Jonathan Chapman’s “Design That Lasts”, CMU School of Design, Spring 2021
Although the plastic toothbrush may seem a ubiquitous element of daily life, the earliest mass-market plastic toothbrushes have not yet reached their centennial. First introduced in the 1930s, these simple brushes have maintained impressive continuity in both form and function. But after just a few months of brushing, many billions of toothbrushes now reside in landfills around the world.
In this post, we’ll explore the full lifecycle of the bestselling toothbrush on Amazon.com, the Colgate Extra Clean Toothbrush, from raw materials through disposal. In a following post, we’ll address potential design interventions to the problems we identify.
How it’s made.
The Extra Clean toothbrush is composed of three materials: thermoplastic elastomer (TPE), polypropylene (PP), and nylon.
To produce this toothbrush, manufacturers first purchase plastic pellets and nylon bristles from petrochemical companies. To fabricate large quantities of two-shot toothbrush handles, automated facilities melt polypropylene pellets into a dough-like consistency, and then inject the plastic dough into a two-part mould.
After the Polypropylene has solidified, a separate mould for thermoplastic elastomer (the plastic rubber grip) is applied on the back of the handle. Handles are released from the mould after cooling. The process is rapid, taking just 10 seconds to create 15 toothbrush handles.
To assemble the nylon bristles, an automated machine selects 22–25 bristles, then injects them into a hole on the toothbrush head. This process takes less than 5 seconds per tooth brush, and is very hygienic.¹
How it’s used.
Roughly 40% of Americans regularly use a powered toothbrush.² For this growing segment, the manual toothbrush now fills a different use case than daily brushing. Rather than serving daily use, the manual toothbrush has become ephemeral, used for the duration of a vacation, unexpected overnighter, or perhaps even a single brushing.
Meanwhile, for the 60% who typically use a manual brush, a longer, slower use case prevails. For these brushers, choosing a new toothbrush color when visiting the dentist or even at the grocery store, becomes a ritualized moment of self-care. Some opt for alternatives like bamboo-handled brushes, or even a small but growing number of modular systems with replaceable brush heads like Etee or Clic.
If properly cared for, the expected lifespan of a toothbrush is just three to four months. But it’s also common to extend that lifespan — people commonly reuse toothbrushes for other purposes: a cleaning brush for the kitchen or bathroom, applying hair dye, and so forth.
How it’s disposed of.
But for the brief use cases of most manual brushes, this useful lifespan is far exceeded by the “deathspan” of a plastic object that may take 1,000+ years to decompose in landfill.³
Despite being made of plastic, most toothbrushes are not individually recyclable because of the difficulty of separating the component materials. Even if the parts were separated, small plastic components like bristles are difficult to capture in the recycling process.³ Although both polypropylene and nylon are highly recyclable materials⁷,⁹ Pittsburgh’s municipal recycling service, like many similar services, doesn’t accept toothbrushes. ¹⁰
And in efforts to address toothbrushes’ poor recyclability, Colgate recently partnered with TerraCycle to upcycle toothbrushes, turning them into marketable consumer products (like furniture, shipping pallets, and storage containers). However, the program is not yet widespread, as one must aggregate 100+ pieces before sending in to earn credits.
What’s left?
Depending on how it was disposed, a toothbrush can follow a couple different paths. Most commonly, toothbrushes are thrown out to a landfill, where the bristles can take 30–40 years to decompose⁴, and the plastic body can take over 500 years to decompose⁵. Not only is decomposition long-lasting, but the chemical products of decomposition can cause severe environmental harm. Polypropylene, for example, can leach lead and cadmium,⁶ both of which are highly toxic.
A toothbrush could also end up in a garbage incinerator to capture its stored energy. In this process, nylon releases fumes containing dioxins and vinyl chloride⁷, the latter of which is explosive, and can cause serious illness and cancer when present in polluted air.⁸
Outro
In this brief post, we sought to establish the journey that a common toothbrush weaves through manufacturing, use, disposal, and decomposition.
In our next post, we’ll present design interventions that we believe could lead to a toothbrush whose useful life and disposal phases are in closer alignment, allowing the improved product to serve a purpose for much more of a shorter stay on Earth.
Sources
- Yves Martin Allard, André Douillard, Gabriel Hoss, Louis-Phillipe Myre. “Electrical Panels/Kites/Eyeglass Frames/Toothbrushes.” How It’s Made, Season 5, Discovery Channel Canada. 29 November, 2005. url: https://www.youtube.com/watch?v=CK5npQc3Oow
- “U.S. Population: Do You Use Power Toothbrushes?” Statista. November 2020. url: https://www.statista.com/statistics/278156/us-households-usage-of-power-toothbrushes/
- Alejandra Borunda. “How Your Toothbrush Became a Part of the Plastic Crisis.” National Geographic, National Geographic Society. 14 June 2019. url: https://www.nationalgeographic.com/environment/article/story-of-plastic-toothbrushes
- “Time It Takes for Garbage to Decompose in the Environment.” New Hampshire Department of Environmental Services. 13 April 2009. url: https://web.archive.org/web/20090413220235/https://www.des.nh.gov/organization/divisions/water/wmb/coastal/trash/documents/marine_debris.pdf
- John Staughton. “How Do We Know Plastic Will Take so Long to Decompose?” Science ABC. 13 October 2020. url: https://www.scienceabc.com/nature/how-do-we-know-plastic-will-take-so-long-to-decompose.html
- Rick Leblanc. “An Overview of Polypropylene Recycling.” The Balance Small Business, Dotdash. 9 May 2019. url: https://www.thebalancesmb.com/an-overview-of-polypropylene-recycling-2877863
- “Nylon.” Wikipedia, Wikimedia Foundation. 5 February 2021. url: https://en.wikipedia.org/wiki/Nylon
- “Vinyl Chloride.” Wikipedia, Wikimedia Foundation. 21 February 2021. url: https://en.wikipedia.org/wiki/Vinyl_chloride
- “The Definitive Guide to Polypropylene (PP).” Omnexus, SpecialChem. url: https://omnexus.specialchem.com/selection-guide/polypropylene-pp-plastic#Recycling
- “Residential Recycling.” Pittsburgh Department of Public Works. url: https://pittsburghpa.gov/dpw/residential-recycling
- “Colgate® Oral Care Recycling Program.” TerraCycle. url: https://www.terracycle.com/en-US/brigades/colgate
12. “How We Recycle.” TerraCycle. url: https://www.terracycle.com/en-US/about-terracycle/how_we_solve
