Now, scientists are reporting that throwing these lenses down the drain at the end of their use could be contributing to microplastic pollution in waterways. They end up in wastewater treatment plants - and that's where things get a little dicey.
Now a research team based in the United States has shown for the first time how they can get eaten by fish and other marine life and be returned to us on our plates.
"When the lens plastic loses some of its structural strength, it will break down physically". Arizona State University researchers in a small survey found that about one fifth of users flushed old lenses down the toilet or sink.
Aquatic organisms can mistake microplastics for food and since plastics are indigestible, this dramatically affects the marine animals' digestive system. "That presents threats to that particular organism and anything that feeds on it" - including humans, further up the food chain.
A new report reveals that a shocking amount of contact lens users - almost 20 percent - dispose of those little plastic circles in a terribly irresponsible way, by flushing them down the toilet or the drain of the sink. "This is a pretty large number, considering roughly 45 million people in the USA alone wear contact lenses".
To make matters worse, because contact lenses are typically denser than water, they can sink into aquatic zones and be eaten by marine life thriving down there, which can potentially poison them.
Analyzing what happens to these lenses is a challenge for several reasons. He said that even though lenses make up a very small percentage of plastics entering lakes and oceans, people should still be taught to put them in with solid waste and not down the toilet or sink. But you might not have realized that even the smallest pieces of plastic, like contact lenses for example, can be a part of the problem.
Many people rely on contact lenses to improve their vision. So, it's unclear how wastewater treatment affects contacts. He pointed out that some manufacturers have already begun recycling programs to reclaim the plastic from lenses.
So the researchers tried to replicate a large waste water treatment facility and exposed five polymers used in contact lenses to the kind of microorganisms found in water treatment plants.
The microbes actually altered the surface of the lenses, weakening the plastic polymers.
Contact lens packages don't now tell users how to dispose of them, said Halden, who suggested that companies should add labels recommending that contacts be put in the garbage rather than washed down the drain. Eastern time in the Boston Convention & Exhibition Center. To ask questions online, sign in with a Google account.
The American Chemical Society, the world's largest scientific society, is a not-for-profit organization chartered by the U.S. Congress. ACS is a global leader in providing access to chemistry-related information and research through its multiple databases, peer-reviewed journals and scientific conferences. "[The study researchers'] method of making assumptions and estimations is quite reasonable", she adds.