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Electric clothes dryers are emitting microfiber pollution directly into the environment. 

Let's talk about our dryers.

It is now well-known that washing machines contribute to microfiber pollution when tiny fibers that shed from clothing and home textiles wash out the washing machine’s drain water. New research, conducted by Cora Ball founder and co-inventor Rachael Miller and microfiber scientist at Central Wyoming College-Jackson and published in PLOS ONE, establishes “that electric clothes dryers emit masses of microfiber directly into the environment. Microfiber emissions vary based on dryer type, age, vent installation and lint trap characteristics” and concludes that, “dryers should be included in discussions when considering strategies, policies and innovations to prevent and mitigate microfiber pollution”. 

You probably recognize Rachael's name as one of the co-inventors and CEO of Cora Ball/Bubbe Clip and co-founder of Rozalia Project. Co-author on this paper is Professor Kirsten Kapp, a wildlife biologist, science teacher, guest scientist on Rozalia Project's expedition vessel, American Promise and more who is also looking at the problem of microplastic (she is also a fellow sailor, skier and longtime friend of Rachael's).

This first-of-its-kind study, funded in part by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health (Grant # 2P20GM103432), links dryer vent emissions with microfiber found in the outdoor environment. Rachael and Kirsten realized that dryers are a contributor to the problem, in fact Rachael started speaking publicly about that in October of 2016. The issue was that there was very little research about dryers and microfiber and none to investigate emissions to the environment or compare total microfiber emitted from the vent and caught in lint traps across multiple machines. We needed more than just observation to be heard. Doing this work over dirt, however, would be a time-consuming and tricky task having to separate microfibers from soil and other organic matter found in terrestrial samples. The game-changer for Rachael and Kirsten is that they realized that if they did the experiment during the winter, they could use the snow as the terrestrial substrate. Since snow turns to water, and filtering water samples is so much easier than soil...that is what they did. 

The sampling team, which included Cora Ball and Bubbe Clip co-inventor, Brooke Winslow, used bright pink polyester fleece blankets in two different household dryers which made identifying the fibers from the experiment very easy (neither households had any fuchsia textiles in use). They set up 14 identical plots outside dryer vents in the two locations and post dryer event, collected snow from a 1' x 1' and 1" deep area at each plot. They found that microfibers that flow out the dryer air vent land beyond the area directly under the vent. While the majority of fibers from the blanket fell within 5’ of the vent, fibers were observed in 5 test plots 30’ from the vent. Results suggest that wind may be a factor. 

Heat map showing distribution and concentration of fibers from the test blanket in the 14 plots that were sampled. The bigger and darker the circle, the more fibers were found at that test location. An important note, the extent of this study was 30’ from the vent, we do not know exactly how far these fibers travel, and how much they contribute to atmospheric microfiber pollution during transport.

In terms of the amount of microfiber released by dryers, this study found that a total of 105 - 209mg of lint, including fibers, is released from one polyester fleece blanket into the environment (outdoor air) via electric clothes dryer exhaust after three dryer cycles. Because this is one of the first studies to investigate dryer emissions into the air and surrounding ground, it was done without pre-washing with washing machines in order to reduce the variables washing machines would have introduced. Rather, the blankets were soaked before drying. Accordingly, this paper does not make an estimate about the total amount of fiber dryers might be contributing to the environment. 

Variations in dryer design, age, and/or installation are a factor in determining the amount of fibers emitted into the environment. There were several differences in the dryers used in this study, most notably: age, length of ducting and size of lint trap screen. The older dryer with longer ducting produced less microfiber emissions. The researchers suspect that is due to fiber buildup in the walls of the ducting. The dryer with the larger lint trap screen (approx. 3 times greater, also the older model) caught more lint than the dryer with the smaller lint trap screen. The authors hope that these initial findings encourage additional studies investigating fiber buildup in ducting, and identifying characteristics that make lint trap assemblies most effective as well as how dryer settings, fill levels, in-drum devices and other design parameters affect both shedding rates and volume of fibers that are emitted with the dryer exhaust.

Fiber captured from dryer exhaust vents. Each petri dish shows the fiber emitted into the air by one polyester fleece blanket that was soaked and then dried in an electric clothes dryer for one complete dry cycle (low heat). A-C represent location 1, and D-F represent location 2. The amount of fibers emitted decreased with each cycle. This is a similar pattern seen with microfiber emissions in washing machines and something that needs further investigation to best estimate total emissions from electric clothes dryers.

For all of us washing our clothes at home

While we learn more about the mechanisms, designs and settings that cause shedding in dryers, we suggest that you only wash and dry when necessary. Where possible, line dry or use an indoor clothes rack. We know that lots of little make a big and the Cora Ball Team will always keep our community informed about the latest science, best laundry practices and solutions that have an impact.

Access the peer reviewed paper for free:

The authors chose PLOS ONE open access in order to make these data accessible to all and encourage additional studies that will both focus on helping consumers reduce their microfiber emissions from dryers by learning about best practices in settings and help the laundry industry do their part in working to reduce microfiber emissions that come from their machines through design, engineering and manufacturing. The authors believe there will be multiple solutions to the problem of microfiber pollution and the development of those solutions starts with understanding the problem. Both authors are available to discuss their findings and additional research that will expedite the design and implementation of solutions and laundering strategies that will reduce microfiber pollution to protect our ocean and planet. 

The paper can be found at this link: 

About the authors:

Rachael Z Miller: Rachael Zoe Miller is an expedition scientist, inventor, National Geographic Explorer and Explorers Club Fellow protecting the ocean. She is Founder of Rozalia Project for a Clean Ocean and co-inventor of the Cora Ball, the world’s first microfiber-catching laundry ball. Rachael leads expeditions yielding results published in peer-reviewed journals (including a first investigation of the Hudson River from the Adirondack Mountains to the Atlantic Ocean) and education programs that inspire thousands. She’s presented worldwide including TedX and The Explorer’s Club. Rachael captains the 60’ sailing research vessel, American Promise, certified hundreds of sailing instructors, trained Navy SEALS to use underwater robots, and mentors young scientists at the NY Harbor School.

Kirsten Kapp: Kirsten Kapp is a biology professor at Central Wyoming College- Jackson, where she teaches a variety of science courses and involves students in undergraduate research. She received her B.S. degree from the University of Vermont in Wildlife and Fisheries Management and a M.S. degree from the University of Wisconsin-Madison in Conservation Biology and Sustainable Development. Her interest in microplastic pollution began in 2014 when she joined co-author Rachael Z. Miller and the Rozalia Project as a guest scientist aboard American Promise, a research vessel that sails along the coast of Maine focusing on marine debris. Since then she has involved her students in research addressing local anthropogenic debris and microplastic pollution, including a first investigation of microplastic pollution in the Snake River from Yellowstone National Park to the Pacific Ocean. 

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