Household washing machines are a major source of so-called "microplastic" pollution - bits of polyester and acrylic smaller than the head of a pin littering ocean shorelines worldwide, researchers say.
Mark Browne and colleagues say that the accumulation of microplastic debris in marine environments has raised health and safety concerns as bits of plastic contain potentially harmful ingredients, which go into the bodies of animals and could be transferred to people who consume fish.
To find how big the problem of microplastic contamination is and where are these materials coming from, scientists looked for microplastic contamination along 18 coasts around the world and did some detective work to track down a likely source of this contamination.
They found more microplastic on shores in densely populated areas, and identified an important source - wastewater from household washing machines.
They point out that more than 1,900 fibers can rinse off of a single garment during a wash cycle, and these fibers look just like the microplastic debris on shorelines.
"Designers of clothing and washing machines should consider the need to reduce the release of fibers into wastewater and research is needed to develop methods for removing microplastic from sewage," they recommended.
The study has been published in ACS' journal Environmental Science and Technology.