Polyester, acrylics and other synthetic fabrics generate thousands of tiny microparticles of plastic every time they are washed and dried, and those particles are ending up in our oceans and coastal beaches, according to two new studies.


Unlike the plastic bags and other trash that forms giant, floating trash islands or the smaller pieces that can often be found in sea creatures' stomachs—like the 3,400 pieces recently recovered from the large intestine of a small green turtle off the coast of Brazil—these microparticles are nearly invisible to the eye, from 1 millimeter down to 10 micrometers in diameter.


But their tiny size adds up. According to a study published online September 6 in the journal Environmental Science & Technology, laundering just one garment made from synthetic fibers can produce more than 1,900 fibers per wash. The worst offenders were fleece fabrics. Polar fleece is often made from polyethylene terephthalate (PET) or other synthetic fibers.


And even though these particles are small, their potential environmental danger is large. According to the study's abstract, "Ingestion of microplastic provides a potential pathway for the transfer of pollutants, monomers and plastic-additives to organisms with uncertain consequences for their health."


Lead author Mark Anthony Browne of University College Dublin in Ireland tested shorelines in 18 sites around the world, representing six continents. They found microplastic contaminates at each site, and observed that the main source of these particles appeared to be sewage. Forensic analysis showed that the polyester and acrylic fibers came from clothing, and therefore from washing machines.


Another study published July 13 in the journal Marine Pollution Bulletin discusses the impact of these plastic particles on the marine environment, although in this case it examined the effect of larger plastic trash that broke down into smaller microparticles due to weathering. According to the study's abstract, "microplastics concentrate persistent organic pollutants (POPs), absorbing other pollutants from the ocean water, making them more dangerous as time goes by. The danger of these POPs to marine life is not yet known, and according to the author, Anthony L. Andrady of North Carolina University, "the potential damage posed by these to the marine ecosystem has yet to be quantified and modeled." Andrady, author of the textbook Plastics and the Environment, concludes that more study is needed to understand the impact of microplastics in the ocean food web.


According to a report on these studies in ScienceNews, an earlier report by researchers in Portugal found that sand-sized plastic pellets found on two coastal beaches contained POPs such as "DDT, polychlorinated biphenyls and polycyclic aromatic hydrocarbons."


According to Ecology Center in Berkeley, Calif., the health effects from humans ingesting polyester include respiratory-tract irritation and skin rashes, while acrylics can cause breathing difficulties and nausea.