Ever wondered what happens to disposable contact lenses when it is time to actually throw them away?
Some scientists at Arizona State University asked that question and discovered that many of them disappeared into the sink or were flushed through the toilet – benefiting the problem of microplastic pollution.
Microplastics are pieces of plastic that have been worn down to small pieces that are smaller than 5 millimeters. They can be harmful to wildlife.
The researchers started an anonymous online survey among 400 people who wear contact lenses or not.
"What we discovered was that about one in five users has contact lenses by throwing them in the bathroom or in the toilet," said lead author Rolf Halden, director of the Center for Environmental Health Engineering at the university, Monday at a news conference at a meeting of the American Chemical Society.
The study was presented at the meeting, but is not published or peer-reviewed, which are considered a gold standard in medical and scientific research.
After being flushed, the lenses float through the wastewater system to sewage treatment plants. Halden said that the researchers tested 11 brands of contacts and found that they did not degrade during the treatment process, but in smaller and smaller pieces of cracks.
The fragments are heavier than water, so they settle in the treated sewage sludge, which is often spread on the land. The lenses can then enter drainage into rivers, lakes and the ocean.
"It sounds like a very small problem, because the lenses themselves are small, but they come through the billions," said Halden. According to the study, about 45 million people only wear contact lenses in the US.
"What we see is that every year billions of lenses end up in US waste water, contributing at least 20,000 kilograms per contact lens per year," said Halden. That is about 20 tons of lenses, according to the study.
Research coauthor Charlie Rolsky said that contact lenses are different than plastics such as straws, plastic bags or polystyrene foam because they are so important to people who wear them.
"It is a very personal high-quality plastic that people take for granted and use every day of their lives," Rolsky said.
Halden said that people do not see the lenses as plastic waste because they feel like liquid, almost like water. They even come in small packages of saline.
But even people who consider themselves environmentally conscious admit that they are flushing their lenses, he noted.
"We have made an almost immortal material, it does not disappear, it is not biodegraded," said Halden.
This is a good thing when it comes to contact lenses, because, according to him, you do not want them to deteriorate in the eye of the user, which could damage vision or become a breeding ground for bacteria.
Contact lenses are a small part of the problem of pollution, Rolsky said, but he hopes that the findings encourage people to think more about how plastic waste can be disposed of.
"This could have been another experiment if a label had been affixed to many of these boxes that was a kind of specification:" maybe throw it away with solid waste and please avoid emptying it "; maybe it would be a different one story, "he said.
Contact carriers must throw their lenses in the trash or recycle them, according to the researchers.