Tumble drying culpable for release of airborne microfibres

Tumble drying laundry releases nearly the same amount of microfibres into the air as those released down the drain when the same load is machine washed.

microfibres
Microscope image of cotton (red) and polyester (black) fibres collected from tumble dryer exhaust (Image: P&G)

This is conclusion of research carried out by a team from Northumbria University and partners at Procter & Gamble whose findings are published in PLOS ONE.

The team found that the use of fabric conditioners and dryer sheets, especially in combination, could significantly reduce microfibre release from tumble dryers.

They also found that lint filters with smaller pores would trap larger masses, resulting in far fewer microfibres being released into the air, and that lint filters were better at capturing polyester fibres than cotton fibres, which indicates that most microfibers released into the air by dryers are likely to be cotton.

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While extensive research has been carried out into the quantities of microfibres released down the drain by washing machines, far less is understood about the release from tumble dryers.

Recent analysis has found that washing laundry could release as much as a million tonnes of microfibres annually worldwide, posing potential risks to aquatic ecosystems.

When these fragments are released into the air during tumble drying with vented dryers, they are said to  pose a risk to the environment, and potentially to human health.

Northumbria University’s Dr Kelly Sheridan worked alongside researchers at Procter & Gamble to measure the quantity of microfibres released during the washing and drying of clothing comprised of polyester and cotton. The research spanned European and North American products and washing conditions and involved over 1,200 garments.

“By measuring microfibres released during the whole laundering process we found that microfibre loss through domestic drying is a huge concern,” she said in a statement.

“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.

“We measured the volume of microfibres released during washing, as well as those captured in lint filters when tumble dried.

Test load in a tumble dryer - Dr Kelly Sheridan and PhD student Chimdia Kechi Okafor (Image: P&G)

“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.

“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.”

Dr Sheridan added: “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. Airborne fibres are just as concerning as those present in wastewater.”

Dr Neil Lant, a Research Fellow at P&G, added: “The recent rises in energy costs have led us all to think carefully about the financial impact of using dryers, but few are aware of their impact on particulate air pollution.

“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.

“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.”

Procter & Gamble has been working with analytical and forensic fibre science experts at Northumbria University for over five years to improve understanding of microfibre release during washing and drying.