Study co-author Rolf Halden, director of ASU's Center for Environmental Health Engineering, said in a statement that he hopes the new research will compel contact lens manufacturers to label their products with information about how to dispose properly of lenses ― that is, in a trash can and not a toilet bowl.
"We found that there were noticeable changes in the bonds of the contact lenses after long-term treatment with the plant's microbes", Kelkar said in a statement.
His team's ongoing survey of contact lens wearers in Arizona, which at last count queried about 400 people, found that about one in five of the participants who wear lenses said they flush them down the sink or toilet.
In the second and third stage, the researchers found out that contact lenses weaken when mixed together with microbes present in wastewater.
By using data from the major contact lens manufacturers about the various types of contacts purchased (daily, biweekly or monthly), the ASU researchers were able to calculate that Americans wear a total of 13.2 to 14.7 billion lenses a year.
The lenses are consequently spread on farmland as sewage sludge, increasing plastic pollution in the environment.
"The plastics may have the capacity of soaking up contaminants, and so the plastic shards. they'll likely be loaded with toxic chemicals, like heavy metals, PCBs [polychlorinated biphenyls] and other things", Halden said. It also includes the first in-depth analysis of how they degrade. "This leads to smaller plastic particles which would ultimately lead to the formation of microplastics", Kelkar says.
Discarded contact lenses are contributing to the rising microplastic pollution in the world's water bodies and could eventually find their way to the human food supply, scientists including one of Indian origin have found.
Analysing what happens to these lenses is a challenge for several reasons.
He added: 'This is a pretty large number, considering roughly 45 million people in the U.S. alone wear contact lenses'. "We'd love to have a dialogue [with manufacturers] and establish a solid protocol for consumers to dispose of or even recycle their contact lenses", Rolsky says.
The researchers are presenting their results today at the 256th National Meeting & Exposition of the American Chemical Society (ACS).
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, researchers said.
The authors of the study surveyed wearers in the U.S. and found that 15-20% of them flick their lenses down sinks and toilets, meaning they will most likely end up in waste water treatment plants. What is more, contact lenses are different from plastics used in other products, such as polypropylene, found in everything from vehicle batteries to textiles. So, it's unclear how wastewater treatment affects contacts.
Aquatic organisms are known to mistake microplastics for food, introducing the indigestible plastics into long food chains. "[The study researchers'] method of making assumptions and estimations is quite reasonable", she adds.