A new study has revealed that drying laundry using a condenser tumble dryer leads to hundreds of tonnes of potentially harmful microfibers being released into waterways and oceans across the UK and Europe.

Researchers from Northumbria University, worked in partnership with scientists at consumer goods giant Procter and Gamble on the study, which is published today (24 May) in the scientific journal PLOS ONE.

The team found that while condenser dryers may reduce the volume of airborne microfibers being released compared to vented dryers, they are still a significant contributor of waterborne microfiber pollution, with more than 600 tonnes of microfibers being poured down household drains.

Both types of tumble dryer produce microfiber pollution. Although recent studies have suggested that moving from vented tumble dryers to condenser dryers could reduce airborne microfiber pollution, their impact on waterborne microfiber pollution has been unknown until now.

Researchers found that condenser dryers in the UK and Europe still produce more than 7,200 tonnes of microfiber annually. Although 91% of this is collected in the lint filter, which many consumers dispose of in their household waste, the remaining microfibers – a massive 641 tonnes, equivalent to the weight of more than 100 adult male African elephants – are collected in the condenser and poured down the drain. This makes condenser tumble dryers significant sources of microfiber water pollution.

However, some appliance manufacturers suggest that consumers should clean their lint filters under a tap. If consumers follow this guidance, it could lead to ten times more tonnes of microfibers entering our waterways. This means that the drying process is causing more waterborne microfiber pollution than the washing process.

To evaluate the environmental impact of condenser dryers, Professor John Dean, from Northumbria University’s Department of Applied Sciences, worked alongside researchers at Procter & Gamble to test loads of new, clean garments as well as dirty laundry sourced from volunteers in Newcastle upon Tyne. They collected and analysed microfibers from several components of each type of dryer.

“It was found that most microfibers released from dryers are collected in the lint filter, thereby preventing release into the environment. However, when you realize that some manufacturers then recommend regular washing of the lint filter under a running tap, this contributes directly to an increase of waterborne microfibre pollution.

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

Dr Neil Lant, a Research Fellow at P&G and their leading scientist on this study, added: “The contribution of washing machines to aquatic microfiber pollution has now been extensively studied and filtration technology is now being integrated into those appliances to mitigate the issue.

“Our recent work in collaboration with Northumbria University has recognised, for the first time, that the most important tumble dryer types used in Europe – condenser and heat pump – can also be significant contributors to aquatic microfiber pollution, especially if users wash lint filters in a sink.

“We do over 7 billion dryer loads in the UK and EU each year, with condenser dryers generating 7,200 tonnes of microfibre. We can prevent around 90% of that from causing water pollution by cleaning lint filters into household waste, but to deal with the rest we’ll need to redesign the air filtration systems in all types of dryers.”