New Study Says Flushing Contact Lenses Contributes To At Least 20 Metric Tons Of Water Waste

A study released by Arizona State University says contact lenses break down into microplastics that enter the marine ecosystem.

Close up of man holding contact lens.
Andrey Popov / Shutterstock

A study released by Arizona State University says contact lenses break down into microplastics that enter the marine ecosystem.

For Rolf Halden, director of the Biodesign Institute’s Center for Environmental Health Engineering at Arizona State University, the research began from a personal anecdote. He wondered what happened to contact lenses after they were used.

“I had worn glasses and contact lenses for most of my adult life,” said Halden, according to the paper released by Arizona State University. “But I started to wonder, has anyone done research on what happens to these plastic lenses after their useful lifespan is over?”

Forty-five million Americans rely on contact lenses rather than glasses to fulfill the prescription corrective needs. The study released by ASU is the first nationwide study to analyze the effects of contact lenses on plastic water waste. The research was performed and presented by Halden, Charles Rolsky, and Varun Kelkar.

“We found that 15 to 20 percent of contact-lens wearers are flushing the lenses down the sink or toilet,” Rolsky said in a presentation to the 256th National Meeting and Exposition of the American Chemical Society (ACS) held in Boston. “This is a pretty large number, considering roughly 45 million people in the U.S. alone wear contact lenses, amounting to 1.8–3.36 billion lenses flushed per year, or about 20–23 metric tons of wastewater-borne plastics annually.”

A beach with a variety of plastic waste.
Plastic water waste is a major ecological concern. Milos Bicanski / Getty Images

Discarding contact lenses by flushing them down the toilet causes many adverse effects to the water ecosystem, reveals the study. From the household drain, the lenses are then diverted to wastewater treatment plants. The treatment plants “fragment them into microplastics, which accumulate in sewage sludge.” The sewage sludge then enters “a pathway of macro- and microplastics from lenses to enter terrestrial ecosystems,” the report’s authors say.

The results are not only harmful to aquatic life, but to humans again down the line.

“Aquatic organisms are known to mistake microplastics for food, introducing the indigestible plastics into long food chains,” says the research. “Some microplastics eventually can find their way into the human food supply,” where they can wreak havoc on human health.

KCCI reports the researchers are already thinking about how they can use the results of the study to improve the health and safety of wastewater.

“A simple first step would be for manufacturers to provide on product packaging, information on how to properly dispose of contact lenses, which is simply by placing them in the trash with other solid waste,” said Halden, as reported by KCCI.