Beijing, Aug. 21 (Xinhua) -- "Cosmetic contacts" can make the eyes appear big and bright, and are essential items for many women who love beauty. However, a new study released at the American Chemical Society Annual Meeting and Exhibition recently warned people not to throw away used contact lenses and other contact lenses, lest they cause microplastic pollution in rivers.

Arizona State University researchers found that in the United States, about 45 million people wear contact lenses, of which 15 to 20 percent of people will throw used contact lenses into the toilet or sink, estimated that the total weight of contact lenses entering the U.S. sewer each year is 6 to 10 tons.

Contact lenses are usually made of silicone hydrogels and other materials, which are plastic. The researchers took five commonly available contact lens materials and exposed them to anaerobic and oxygenophilic microbes used in wastewater treatment plants. They then tested them with Raman spectroscopy. They found that after long-term treatment with microorganisms used in sewage treatment plants, the contact lenses physically degrade and eventually form microplastics.

These microplastics can be released into the natural environment with treated sewage, where they pose a threat to aquatic life.

Aquatic organisms can mistake microplastics for food, but plastic can't be digested, so this could affect their digestive systems, said Charlie Rolskye of Arizona State University, one of the researchers. Some aquatic life could end up in the human food supply chain, which means humans could be exposed to both the microplastics and the contaminants that cling to their surfaces.

The researchers are calling for contact lens manufacturers to include tips on packaging reminding people not to throw discarded contact lenses down the drain, but to dispose of them with other solid waste.

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