A team of researchers from Arizona State University estimates 6 to 10 metric tons of contact lenses end up in U.S. wastewater treatment plants annually

A new study, presented at the National Meeting & Exposition of the American Chemical Society, found that contact lenses are a major source of microplastic pollution in waterways. The study, led by researchers from Arizona State University, estimated that anywhere from 6 to 10 metric tons of plastic contact lenses end up in wastewater treatment plants in the U.S. annually. The researchers found that contact lenses are denser than water and transparent, making them difficult to detect in wastewater. Based on a survey, the team found that 15% to 20% of contact wearers flush the lenses, leading them to wastewater treatment plants.

In order to assess how contact lenses break down in wastewater treatment plants, the team simulated the treatment process by exposing five polymers found in 112 brands of lenses to anaerobic and aerobic microorganisms present at wastewater treatment plants for varying times and performed Raman spectroscopy to analyze them, according to Science Daily.

“We found that there were noticeable changes in the bonds of the contact lenses after long-term treatment with the plant’s microbes,” said Varun Kelkar, a researchers from the Biodesign Institute’s Center for Environmental Health Engineering at Arizona State University.

Overall, the team concluded that microbes in wastewater treatment plants altered the surface of the lenses, weakening them and breaking them into microplastics. The team hopes their study will raise awareness for the proper disposal of contact lenses and lead manufacturers to conduct further research on the impact on aquatic life.

“What we find is that there are billions of lenses ending up in U.S. wastewater every year,” said Lead Author Rolf Halden. “They contribute a load of at least 20,000 kg per year of contact lenses.”

Listen to our podcast, Talking Under Water Episode 2: Pollution in Waterways, to hear editors from Water & Wastes Digest, Storm Water Solutions and Water Quality Products discuss the issue of microplastics in waterways.