When you clean out your dryer lint screen, you get a clump of fluff that comes from your clothes and other laundry. But that's not the only place these fibers are going.

Sometimes they never even make it to the dryer.

According to new research, 60% of the microplastics in our fresh water come from laundry fibers. When we wash our clothes, towels and sheets, microfibers break off and wash away. They make their way into wastewater treatment facilities and from there, to lakes and other large bodies of water.

"I was surprised although, like, you kind of go 'Oh I really shouldn't have been,' " Penn State Behrend chemist Sherri Mason tells Scientific American. "Because we all clean out our lint filters on our dryers. We should be like, 'Oh of course if it's coming off in the dryer that whole process is starting in the washer.'"

Mason analyzed 90 water samples taken from 17 different water treatment facilities across the U.S. In her report, which was published in American Scientist, Mason found that each facility was releasing an average of more than 4 million pieces of microplastic into waterways every day. Of those microplastics, 60% are fibers from clothing and other fabrics. A little over a third are from microbeads — tiny plastic specks used in personal products, that were banned in the U.S. in 2018. The remaining 6% are from films and foams.

Natural materials also shed fibers in the washing machine and dryer, but Mason says microbes are able to digest them, but the same isn't true for fibers made from synthetic textiles. Those are non-biodegradable and may linger in the ecosystem for centuries.

Making their way into fresh water

wastewater treatment facility Wastewater treatment plants weren't built to filter out microplastics. (Photo: Montgomery County Planning Commission [CC BY-SA 2.0]/Flickr)

Mason points out that there are 15,000 wastewater treatment facilities in the U.S. They were designed to remove urine, fecal matter and microbes that can negatively impact the environment. But they weren't built to remove plastics. Some studies show that treatment facilities can remove somewhere between 75% and 99% of microplastics. But billions of these microplastics still make their way into our fresh water. A study published earlier this year in called Human Consumption of Microplastics found that Americans eat, drink and inhale between 74,000 and 121,000 microplastic particles each year.

Mason says information is power and consumers are taking action. Just like microbeads were banned, people are working to reduce plastic production and consumption. She suggests that each person can reduce plastic use while also lobbying businesses to use alternative materials and reusable containers.

"The plastic we use ultimately comes back to us in the food we eat and the water we drink," Mason says in her report. "Although this is scary and a bit distressing, it also means we can make positive changes."

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.

The biggest source of microplastics in fresh water is laundry lint
Microplastics in fresh water are primarily laundry lint that comes from washing machines, and they end up in your drinking glass.