Tumble dryers can cause air pollution through microfibres, but dryer sheets and fabric softener can help: study

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Opting for hanging the laundry up to dry instead of throwing it in the tumble dryer could cut in half the amount of pollution the laundry process creates, according to the results of a new study.

A paper published in the journal PLOS One Wednesday found that using a tumble dryer releases the same amount of potentially harmful microfibres as running the washing machine does, and that using laundry products such as fabric conditioner could cut down on those microfibres.

“By measuring microfibres released during the whole laundering process we found that microfibre loss through domestic drying is a huge concern,” Dr. Kelly Sheridan, an expert in clothing fibres at Northumbria University and one of the authors of the study, said in a press release.

“Ours is the first study that has simultaneously quantified microfibres released from clothing during washing alongside that released when the clothing is then tumble dried.”

Microfibres are tiny fibres released from clothing and other textiles through wear and cleaning processes. Since clothes are often made from synthetic fabrics, such as polyester, synthetic microfibres are one of the most common sources of microplastics, making their release into our environment a little-understood form of plastic pollution.

The intent of the study was to measure the release of microfibres in washing and drying and whether the use of products such as dryer sheets and fabric conditioners could reduce that number.

Although microfibres being released into water and potentially draining into aquatic environments has been studied, less is known about the impacts of microfibres released into the air by a dryer.

According to researchers, the microfibres that make it through a dryer’s lint catcher could end up polluting the air and potentially causing harm to the human beings living in that home and breathing that air on a regular basis.

“It is critical to our understanding of the impact of microfibres on human health and the environment that all the potential pathways for microfibre release, including air, are assessed,” Sheridan said. "Airborne fibres are just as concerning as those present in wastewater.”

Scientists from Northumbria University worked with scientists from Procter & Gamble to test the washing and drying of clothing made of polyester and cotton, a process involving over 1,200 garments.

PLOS One noted that the authors of the study do have competing interests in that several are employed by Procter & Gamble, which “is a manufacturer of fabric care products such as laundry detergents, fabric conditioners and dryer sheets,” but stated that the study data still adhered to their policies.

The study explained that tumble dryers release warm air through a vented pipe as they work and although these dryers come with a lint catcher, they don’t always filter everything out.

“Our study found that domestic dryers produce comparable quantities of microfibres that could be released to the air as we already see going into our water systems from a standard washing cycle,” Sheridan said. “While many microfibres can be captured in lint filters during drying, if the pore size is too large, a significant amount will be released into the air, comparable to the amount released down the drain in washing.”

Researchers ran test loads of laundry that contained 10 shirts made of cotton and 10 shirts made of polyester, using both European and North American washing conditions and measured them at different stages in the washing and drying process to see how many microfibres were released down the drain of the washing machine, collected in the lint catcher, or released into the air.

When conventional fabric softener was added during the rinse cycle, although it did not change the amount of microfibres lost in the washing machine, more microfibres were caught by the lint catcher in the dryer, showing up to a 21 per cent reduction in microfibres released into the air.

Tumble dryer sheets used in the dryer also reduced microfibres released into the air, likely by collecting some themselves, the study suggested. Tumble dryer sheets and fabric softener used in combination during the cleaning and drying of one load showed a 45 per cent reduction in microfibres released through the dryer vent.

The study also found that lint catchers that had a tighter mesh were much better at capturing microfibres.

“These latest findings are a call to action for the appliance industry to improve the efficiency of fibre filtration systems in vented dryers and drive the conversion to condenser dryers with no airborne fibre release, especially super energy efficient heat pump dryers,” Dr. Neil Lant, a research fellow at P&G and the leading scientist on the study, said in the release.

“While we know that people in different parts of the world and in different types of households may choose alternative ways to dry their clothing, our findings in this study relate to the impacts of vented tumble drying. Further research would be needed to assess the impacts of other drying methods.”