When we think of the sources of microplastic pollution, the first thing that comes to mind is usually microbeads. These types of plastic pollutants make up a huge percentage of the microplastics that accumulate in the oceans, but they are not the only ones. Secondary microplastics come from bigger plastic items that have already broken down and, as it turns out, they include a number of items we probably never consider in connection to plastic waste. In fact, a new study from researchers at Arizona State University found contact lenses that have been incorrectly disposed of constitute between six to 10 metric tons of waste in U.S. waters.

The results of the study, presented at the 256th National Meeting & Exposition of the American Chemical Society, showed that flushed contact lenses greatly contribute to microplastic pollution because of the way wastewater is treated, Inverse reports. The study was one of the first to examine the way contacts, which are made of soft plastics like poly(methyl methacrylate), silicones, and fluoropolymers, find their way into the water and what happens to them next.

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“This began as an exploratory venture but we have information to support the fragmentation of contact lenses into microplastics within a wastewater treatment plant,” Charles Rolsky, study Co-author and Arizona State University Graduate Student, told Inverse.

The study was made up of three parts. In the first, the team surveyed 139 people to learn how contact lenses get into wastewater. It was discovered that 19 percent of wearers flushed their contacts down the sink or toilet. The contact lenses travel through sewer pipes and finally get funneled into wastewater treatment plants. The second and third part of the study revealed that contacts become weakened when they are mixed with microbes in the wastewater, which makes them break down into smaller pieces, and in the end become microplastics which cannot be filtered out from the water the way bigger pieces of plastic can.

Once they are turned into microplastics, broken-down contacts travel into the environment, pollute the waters and wildlife habitats, get ingested by marine animals, can cause blockages, and leach toxins into their bodies. If not, these plastics make their way into seafood and drinking water, both tap and bottled. Rolsky emphasizes the fact that microplastics from contact lenses are denser than water and can sink to the seabed and be eaten by bottom feeders.

Every day, around 45 million Americans use contact lenses, and that number is still rising. The convenience that contact lenses bring of course does not need to be sacrificed – the answer to the problem lies in learning how to dispose of them properly and then acting accordingly. Contacts should never be flushed but simply thrown in the trash can. Some contact recycling programs already do exist, but they are not yet widespread. For now, the researchers suggest that contact lens manufacturers should put a label on their products, clarifying what is the best and correct way to dispose of them.

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To learn how you can minimize your use of single-use plastics and properly dispose of the ones you do use, check out One Green Planet’s #CrushPlastic campaign!

Image source: n4i/Flickr