Tumble dryers are a 'major source of plastic pollution' and can discharge 120 million tiny fibres a year

Tumble dryers have emerged as a major source of microplastic pollution after scientists found that a single machine could discharge up to 120 million tiny fibres a year into the atmosphere.

This is the first major study into the environmental effect of clothes washing to look at tumble dryers rather than washing machines and finds that the drying process releases up to 40 times more fibres per garment.

These pose a risk to wildlife which can ingest them as they float in the air, settle on the land and get washed into rivers. And they can potentially end up on the dinner plate as they enter the food chain.

Furthermore, the particles can absorb harmful chemicals that can later leached out into the systems of any person or animal that breathes them in.

"Tumble dryers are a major source of microplastic pollution in the world," Kenneth M Y Leung, of the City University of Hong Kong, told i.

"Polyester and other artificial fibres do not break down and can remain in the environment for a long time. That is a worrisome consequence," he said.

The air used in tumble drying typically passes through a duct, or tube, and is vented directly outdoors – and researchers called on manufacturers to develop and install a filter that can cut down on the release of plastic microfibres during this process.

Households should, researchers suggest, try to dry polyester and other synthetic clothing on washing lines or radiators where possible – something that is relatively easy to do since these materials dry more easily than natural fibres like cotton and wool, the researchers say.

They also suggested that people who do tumble dry synthetic garments, to do them in small loads as the volume of microplastics released per garment increases with load size because the levels of friction between garments rises sharply the fuller the machine is.

Dr Leung was given the idea for his research after the duct tape from his machine disconnected from the window and the pipe became loose.

"After an hour I went back to the kitchen and there were fibres everywhere and it took me hours to clean up," he said.

In their tests, the researchers separately dried clothing items made of polyester and those made of cotton in a tumble dryer that had a vent pipe to the outdoors.

As the machine ran for 15 minutes, they collected and counted the airborne particles that exited the vent.

For both fabrics, the dryer released between 1.4 and 40 times more microscopic fragments than were generated by washing machines in previous studies for the same amount of clothing.

They also found that the release of polyester microfibers increases with more clothes in the dryer.

The researchers estimated that between 90 and 120 million microfibres are produced and released into the air outside by the average single Canadian household's dryer every year.

The release of cotton and other natural fibres is not viewed as a significant environmental hazard as they break down quite quickly.

The study is published in the journal ACS’ Environmental Science & Technology Letters.