August 19, 2018
Arizona State University scientists are reporting the first nationwide study that shows consumers, by discarding used lenses down the drain, may be unknowingly contributing to plastic pollution.
“We found that 15 to 20 percent of contact-lens wearers are flushing the lenses down the sink or toilet," said Charles Rolsky, a PhD student who worked with sustainability scientist Rolf Halden on the study. “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."
Lenses that are washed down the drain typically are conveyed to wastewater-treatment plants. The study showed that wastewater plants fragment them into microplastics, which accumulate in sewage sludge. For about every two pounds of wastewater sludge, a pair of contact lenses typically can be found.
Sewage sludge is an abundant material routinely applied on land for sludge disposal and soil conditioning, thereby creating a pathway of macro- and microplastics from lenses to enter terrestrial ecosystems where potential adverse impacts are poorly understood, Halden said.