Why you shouldn’t flush away old contact lenses

Leslie Hanson
August 21, 2018

"This began as an exploratory venture but we have information to support the fragmentation of contact lenses into microplastics within a wastewater treatment plant", said Charles Rolsky, one of the study's authors and a graduate student at ASU.

That is because lenses do not break down completely in sewer systems.

According to the team of researchers, up to 20 percent of contact lens users flush them down the toilet after use. They interviewed workers at municipal sewage plants who confirmed they had seen lenses in wastewater, the researchers told The New York Times. "This leads to smaller plastic particles which would ultimately lead to the formation of microplastics". Currently, researchers are stating that disposing of these lenses down the drain could be adding to microplastic pollution in waterways.

These differences make it hard to process contact lenses in wastewater plants. Rolsky and his co-authors presented the results Sunday at the annual meeting of the American Chemistry Society.

Rolf Halden, director of the Biodesign Center for Environmental Health Engineering at Arizona State University who directed the study.


The first part was an anonymous survey of 139 contact-lens wearers and non-wearers. "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". In fact, the team estimates that at least six metric tonnes of lenses end up in wastewater each year in the US alone. 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, Halden says. The lenses are very hard to spot in wastewater since they are transparent.

It turns out the best thing you can do is to throw them in the bin alongside other household waste, according to the report authors. "So I would be concerned that there would be more of an impact with these microplastics than with the other materials due to their ability to absorb various toxins in the environment, like pesticides and herbicides, and really hyper-concentrate these chemicals and move them into the food chain and up the food chain". Secondly, contact lenses are made of a special kind of plastic. Halden said the researchers tested 11 brands of contacts and found that they don't degrade during the treatment process but tear into smaller and smaller pieces.

These differences make processing contact lenses in wastewater plants a challenge.

The scientists are concerned that fragmented lenses cause aquatic life such as fish to mistake them for food.

Earlier research on the individual waste from an average person's disposable contact lenses in the United Kingdom looked more broadly at the environmental footprint of contacts and compared it to waste from soda cans, suggesting that the lens-related waste is relatively small, per person-roughly equivalent to the disposal of 15 cans of Coca Cola per year. They hope their work will determine industry to at least provide labels on the lenses' packages describing how to properly dispose of the devices - placing them alongside other solid waste.

Other reports by Iphone Fresh

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