News Feature | August 29, 2018

Contact Lenses May Slip Through Wastewater Systems

Sara Jerome

By Sara Jerome,

Flushing contact lenses is contributing to water pollution because lenses do not break down entirely in wastewater treatment systems, according to a new study.

“Americans use about 14-billion contact lenses every year, resulting in an estimated 50,000 pounds winding up in sinks and toilets,” WTOL reported.

Researchers presented the findings at an American Chemical Society event in August, according to the organization.

“The team estimates that anywhere from six to 10 metric tons of plastic lenses end up in wastewater in the U.S. alone each year. Contacts tend to be denser than water, which means they sink, and this could ultimately pose a threat to aquatic life, especially bottom feeders that may ingest the contacts,” the statement said, citing researcher Rolf Halden.

Exactly what happens to contact lenses at wastewater plants is tricky to nail down.

“First, contact lenses are transparent, which makes them difficult to observe in the complicated milieu of a wastewater treatment plant. Further, the plastics used in contact lenses are different from other plastic waste, such as polypropylene, which can be found in everything from car batteries to textiles,” the statement said.

“Contact lenses are instead frequently made with a combination of poly(methylmethacrylate), silicones and fluoropolymers to create a softer material that allows oxygen to pass through the lens to the eye. So, it's unclear how wastewater treatment affects contacts,” it continued.

As research on microplastics accumulates, wastewater industry experts are debating how treatment processes could be altered to mitigate the problem.

“It is well established that the oceans contain significant accumulations of plastic debris but only very recently have studies began to look at sources of microplastics in river catchments,” according to one recent study, published in Environmental Science and Pollution Research.