His research showed that between 15pc and 26pc of users in the U.S. throw them down the sink or toilet.
Five different polymers that can be found in contact lenses were matched to microorganisms in various wastewater treatment facilities.
By their estimates, between six and 10 metric tons of plastic lenses are ending up in US wastewater plants every year, adding to the problem of microplastics in oceans, lakes and even commercial bottled water. These microplastics can not be filtered out of the waste water unlike larger plastic particles. 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. It is common for a person to have multiple pairs of lenses and some of them are disposed off after a few months of use.
Lenses that are washed down the drain ultimately end up in wastewater treatment plants.
A number of people depend upon contact lenses to enhance their vision.
Here & Now's Peter O'Dowd speaks with Rolf Halden, professor, director of the Center for Environmental Health Engineering at the Biodesign Institute and one of the authors of the new study.
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About 15 to 20 percent of contact wearers are flushing the lenses down the sink or toilet in the United States and roughly 45 million people in the US wear contact lenses, according to the study.
"We found that 15 to 20 per cent of contact wearers are flushing the lenses down the sink or toilet", said Charlie Rolsky, a PhD student at ASU.
The researchers also tested what happened to contacts in liquids of varying densities, finding that they always sink to the bottom.
Halden said people don't think of the lenses as plastic waste because they feel like fluid, nearly like water. The team collected parts of the lenses from the sludge and analyzed them.
Aquatic animals can mistake fragments of microplastic for food - and the plastics can even wind up back in the human food supply, along with any of the contaminants that tend to stick to plastic. But unlike the daunting task of slashing grocery bag and water bottle use, there's an easy way to prevent contact lenses from becoming pollutants, the ASU researchers note. Therefore, it is unclear how wastewater treatment impacts contacts. "We found that there were noticeable changes in the bonds of the contact lenses after long-term treatment with the plant's microbes", says Kelkar. "The minimum object size for recycling in 40mm, which is why some items like plastic straws and small soy sauce bottles that come in sushi packs can not be recycled".
Those ASU researchers are also calling on contact lens manufacturers to provide product packaging information on how to safely dispose of the lenses.
Millions and millions of Americans put on contact lenses each day, but a lot of them probably aren't aware that these thin circular strips of plastic pose great harm to the environment.