Household tumble dryers are an overlooked problem for the environment, writes a team led by Kai Zhang and Kenneth Leung from City University Hong Kong after an experiment with the devices. The group found that dryers, when in use, release one and a half to 40 times as many microscopic particles from clothing as a washing machine. And unlike this one, whose wastewater is freed from the particles in the sewage treatment plant, the microfibres from the dryer get into the environment unfiltered.
This is what Zhang, Leung and their team write in the journal “Environmental Science & Technology Letters”. They tested a commercially available dryer with laundry items made of cotton and polyester. In both cases microfibers were released. The problem with polyester fabrics is more serious: on the one hand, the more laundry is put into the drum, the output increases; on the other hand, polyester is a plastic, so the microfibers are to be regarded as microplastics. In contrast to cotton, they are not broken down in nature. Instead, they can accumulate in the food chain, for example. Microplastic particles also act as concentrators for environmental toxins. In the ecosystems, but also in the household, they are now ubiquitous.
The group attributes the difference between cotton and polyester to the fact that the cotton fibers clump together and sink, while the polyester fibers remain floating. All in all, the authors of the study estimate that when a dryer is operated regularly, between 90 and 120 million microscopic fibers are released into the ambient air each year.
In their tests, the group used a dryer that vented to the outside through a hose. The exhaust air was sucked in on the spot and then analyzed in the laboratory. In their opinion, a special filter system should be used at this point in the future, with which the entry of microfibres could be reduced. In the long run, however, materials like polyester should be replaced by more environmentally friendly alternatives. The extent to which the results of their tests can be transferred to condensation dryers, which dehumidify the exhaust air by means of condensation and do not lead it directly to the outside, does not emerge from the study.