Hong Kong Study: Tumble Clothes Dryers Generate Air Pollution from Microfibers

Hong Kong Study: Tumble Clothes Dryers Generate Air Pollution from Microfibers 1

By Jerri-Lynn Scofield, who has worked as a securities lawyer and a derivatives trader. She is currently writing a book about textile artisans.

Microfibers – pieces of microplastics less than 5 mm in length – are now virtually ubiquitous, found in pristine environments such as the Arctic, as well as in human placentas.

Their impact on human health has not been well studied,  although recent research suggests they may be dangerous, as The Guardian noted in Tumble dryers found to be a leading source of microfibre air pollution.:

…In 2021, scientists found microplastics caused damage to human cells in the laboratory. These tiny fibres have also been linked to intestinal inflammation and other gut problems.

A study published this week, Microfibers Released into the Air from a Household Tumble Dryer, found that a single home clothes dryer could release up to 120 million such particles into the air each year, making microfibers so released a leading source of such air pollution (see full study here.)

The study was conducted by a group led by Prof. Kenneth Leung, director of the State Key Laboratory of Marine Pollution (SKLMP) and department of chemistry at City University of Hong Kong. Per the abstract:

This study quantified the number of the two most common textile fibers discharged from a household vented tumble dryer to ambient air. The results suggest that driers of this type are a potential source of air contamination by microfibers, releasing 433,128–561,810 microfibers during 15 min of use. Microfibers can be generated from both polyester and cotton textiles. The abundances of microfibers of polyester produced were directly proportional to the masses of clothing loaded into a dryer, but such a relationship was not apparent for cotton textiles. On the basis of the results presented here and other relevant data, it was estimated that the average Canadian household can annually release from 9 × 107 to 12 × 107 microfibers from a single dryer. To minimize the release of these microfibers into the air, an appropriate engineered filtration system should be developed and adopted as an effective control measure for individual household driers.

Both organic – e.g., cotton – and organic – polyester – shed microfibers when clothes are tumble dried. The natural fibres can be digested and decompose relatively quickly. The inorganic fibres are more problematic. Per the study:

Cotton microfibers discharged into the environment can be ingested by organisms, but they are not as persistent as polyester microfibers. For the same drying duration, cotton textiles produce more stable amounts of microfibers (165 ± 27) after drying regardless of the mass of textiles in the dryer. In comparison, polyester textiles can generate more microfibers than cotton textiles according to the current results. Micro- fibers generated from polyester textiles are of special concern since their bioaccumulation potential increases with decreasing size. The microfibers might be ingested by organisms ranging from zooplankton to fish and birds and transferred into food webs. [Jerri-Lynn here: my emphasis; study p. D, citations omitted.]

Professor Leung told The Guardian that filtering such pollutants is a relatively simple exercise:

“Once we know the source, we can begin to control it using simple methods,” said Leung, the lead author of the study published in the journal Environmental Science & Technology Letters.

Leung’s team has designed filtration systems that prevent washing machines from dispersing microfibres and is now working on similar systems for clothes dryers.

The challenge arises when it comes to dispose of the microfibers that the filters  collect: Over to The Guardian:

“These [filter systems] effectively remove most of the microfibres from the laundry,” he said. However, it is still unclear where these microplastics would end up when the filters were cleaned.
“If people just put these [fibres] in the dustbin, some of the fibres will be released back into the air,” he said. “We suggest the particles should be collected in a bag.”

The question of course is: where does that bag go? Because if it’s simple tossed into a landfill those microfibers will make their way into the ecosystem.

Filters per se are not a complete solution. Instead, Leung noted:

Even if fitting these filters is “possible, as Leung says, microfibres will still be pervasive until the clothing industry uses more environmentally friendly fabrics.

To be sure, the study suggested that when comparing the tumble drying of organic and inorganic fibers, cotton appears superior to polyester. Yet as I’ve written previously, merely shifting production from inorganic fibers to cotton creates its own set of environmental concerns. Current varieties of the most commercially popular cotton are notoriously thirsty plants, and considerable quantities of pesticides are also employed in most cotton production. While organic cotton production dispenses with the pesticides, the thirst issue remains. Reviving traditional Indian cotton varieties holds out some promise in addressing  these issues, yet at present, the scale of such initiatives is minuscule, and alone they couldn’t supply world cotton demand any time soon ( see Growing Cotton: One Small Sustainable Solution to the World Plastics Problem.)

Perhaps another possible short-term solution might be to air dry clothing – doing so cuts back on the fossil fuels necessary to run dryers. My mother used a clothes line during the temperate New Jersey summers of my youth. Yet with temperatures hovering below freezing today in much of the Northeast, clothes hung out to dry would freeze before they dried. Additionally, although Leung et al’s study only addressed tumble drying, I believe his team has also found washers also generate microfibers, so even eliminating clothes dryers completely wouldn’t solve the problem.

Leung et al’s study makes it clear that the typical household clothes dryer generates a considerable quantity of microfibers. Alas, sorting out what should be done to collect and dispose of these fibers properly is not a straightforward task.


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