Focusing on the fate of flushed contact lenses

As many as 45 million people in the US wear contact lenses, but what happens to those disposable silicone hydrogel hemispheres once their daily, biweekly, or monthly wear life is over? A new study suggests that many contact lenses get flushed down the drain and become microplastic pollutants (Environ. Sci. Technol. 2020, DOI: 10.1021/acs.est.0c03121). Arizona State University’s Rolf U. Halden, Charles Rolsky, and Varun P. Kelkar simulated what would happen to contact lenses in a wastewater treatment facility. They determined that lenses don’t break down chemically but instead break into smaller fragments. The ASU team then examined sewage sludge and indeed found such lens fragments. To get a sense of how often contact lenses are flushed away, the team surveyed contact lens users on their disposal habits. They found that roughly 20% of users put their lenses down the drain. This practice, the researchers estimate, could result in 44,000 kg of lens material discharged into US wastewater each year. Halden says that amount—even though a small fraction of the overall plastic waste entering the environment—is worrisome. “It illustrates our broken relationship with a ubiquitous, mass-produced material that has no end-of-life strategy and that likely will outlive not only all humans currently alive but humanity itself,” he says. Halden advises contact lens users to not flush their lenses and to consult their optometrists about recycling options.