Hundreds of thousands of tiny strands of plastic lint are released into wastewater each time you run a load of synthetics. Many of these microplastics end up in the oceans - and their full effects are still not known.
Running clothes made of synthetic fibers through a washing machine at normal temperatures causes vast numbers of tiny plastic fibers to be released into wastewater, researchers at the International Marine Litter Research Unit at Plymouth University in England have found.
The research is the first that quantifies laundry lint as a source of plastics pollution - adding to existing concerns over larger and more visible varieties of plastic trash, which has led to measures like bans on plastic shopping bags.
Just how many plastic fibers were released during a laundry cycle depended on the fabric, as well as the type of detergent: A typical 6-kilogram (13-pound) washing load of acrylic-fabric items (like fluffy blankets) generated more than 700,000 individual fibers.
A load of polyester fabric (like fleece sweaters) generated nearly 500,000 polyester fibers, and a load of polyester-cotton blend clothing generated about 140,000 fibers. Average fiber lengths ranged from 5 to about 8 millimeters in length.
So why does that matter?
Data lacking on effects
"The quantity of microplastic in the environment is expected to increase ... and there are concerns about the potential to have harmful effects if ingested," researchers Imogen Napper and Richard Thompson wrote in their report.
Other studies have shown that such fibers can be found in waters downstream from sewage treatment plants. Even though wastewater from washing machines normally gets filtered through sewage treatment facilities, tiny pieces of lint don't always get filtered out.
A sample of plastic garbage sieved from a river in Maryland - some of it is lint from synthetic fabrics
Which is why "fibers released by washing of clothing could be an important source of microplastics to aquatic habitats," as the authors wrote.
The full effects of plastic microfibers as they float around in the world's seas and lakes are not clear. Research has shown that large quantities of them are ingested by marine organisms, ranging from zooplankton through crustaceans and fish, to seabirds and marine mammals.
Humans eventually close the food circle by eating fish and seafood.
Another recent report by Greenpeace report reviewed scientific literature, with a special focus on microplastics under 5 millimeters in length - including spheres, fragments, or filaments such as those released from washing of synthetic fabrics.
"We now know that microplastics in the sea could have an even greater effect than macroplastics," the Greenpeace report stated.
Macroplastics are big pieces of plastic, such as bits of fishing net or discarded six-pack holders, which often strangle fish, birds, or marine mammals that get entangled in them.
Because they're so small, microplastics have the potential to be ingested by a far larger number of marine organisms. The surface of microplastics can absorb and leach toxic chemicals, so they also serve as rides for hitchhiking poisons.
"Many of the chemical additives and contaminants found to be associated with microplastics, or that are known to accumulate readily on the surface of microplastics, are certainly of significance to human health, as well as to that of wildlife," the Greenpeace review stated.
By taking samples in various oceans, researchers have found that microplastics are now ubiquitous in the oceans, and that the ingestion of microplastics by marine organisms is widespread. So far, however, not much detail is known about how microplastics affect marine food webs.
However, field studies and controlled experiments have shown that ingestion of microplastics by fish or crustaceans diminish digestion, can have serious impacts on the intestines of fish, and can reduce the vigor of marine organisms ranging from lugworms to crabs.
It's not clear whether micropastics, or any toxins they might carry, can "bioaccumulate" up the food chain when humans eat fish or shellfish.
Tiny plastic beads used as additives in personal hygiene products are another form of microplastics pollution
Dealing with the problem
The Plymouth University researchers were careful to say that while they advocate a reduction in the amount of plastic microfibers getting into the environment, they're not promoting a ban on synthetic textiles - similar to a ban on plastic microbeads.
In the case of microbeads, set for a ban in the US by mid-2017 for example, "one of the considerations guiding policy intervention was the lack of clear societal benefit from incorporating microplastic particles into the cosmetics, coupled with concerns about environmental impacts," Thompson said.
But the societal benefits of textiles are without question, Thompson pointed out. "So any voluntary or policy intervention should be directed toward reducing [microplastic lint] emissions, either via changes in textile design or filtration of effluent, or both."