Add millions of used contact lenses to the plastic waste that finds its way into oceans and lakes.

A new study released on Sunday estimates that these smooth transparent discs, essential for the sight of an estimated 45 million Americans are often flushed into the sewer instead of being trashed or recycled.

They are only worn one day a day and thus contribute to the danger that they can eventually become polluting. more, river or going out to sea, says the study that is being presented at a conference by researchers at Arizona State University.

"I wondered what happened to these lenses," says Rolf Halden, director of ASU's Biodesign Institute for Environmental Health Engineering. "In the bathroom they can get lost in the sink or go to the bathroom. I am an engineer, so let's see how big the problem is."

The answer is that the problem is substantial. . Up to 20 percent of the carriers do not throw their old lenses into waste containers, but instead for disposal in sinks and toilets. But because lenses are made of such hard plastics, they do not break completely when they are exposed to microbes. The ASU study showed that after passing a sewage treatment plant, they become even smaller particles that can find their way into fish, birds or other animals.

Of the approximately 14 billion contact lenses used every year in the US, the study estimated that up to 50,000 pounds would be washed away or would otherwise go to the drain, mostly intended for waste processing plants. How many got into the ocean or waterways could not be determined.

It is a similar problem to other wreckage in daily life, from straws and forks to plastic bags. Acknowledgment of the number of plastic straws that eventually ends up in the trash, and ultimately the ocean, has made Starbucks say that it will gradually reduce it in 2020. McDonald & # 39; s plans to test alternatives in the US later this year.

Researchers can find only one maker, Bausch + Lomb, who is seriously pursuing a recycling program for contact lenses. Since the program started in November 2016, the company says that the One by One program has collected packaging waste and 2.5 million used lenses for around 7 tonnes of waste.

"We go through it every year and continue to make us aware of it," said Bausch + Lomb, spokeswoman Kristy Marks.

Johnson & Johnson, which makes about 5 billion contact lenses annually through its popular Acuvue brand, tackled the problem by reducing the amount of paper in the packaging and the amount that can be recycled. It has not emphasized the lens itself, which says that it weighs only 30 micrograms.

The ASU study, that was formally presented Sunday at a meeting of the American Chemical Society in Boston, found that used contact lenses are common in waste water sludge after sewage treatment. A few leftover lenses can usually be found in every 2 pounds of sludge, according to Charles Rolsky, a doctoral student who also worked on the research.

The problem is that because sludge is often deposited on the land, which can eventually wash lenses in lakes or rivers where fish can consume them.

The answer, according to Halden, is not to ban contact lenses. Too many people, including himself, depend on them. And daily disposables, instead of those that carry people for a week or longer, are one of the fastest growing parts of the market for contact lenses and more convenient and safer.

On the contrary, he said the better solution is to encourage proper removal. For its program, Bausch + Lomb is working with a company called TerraCycle that specializes in recycling smaller items that would not normally be separated in the standard process.

The problem with lenses is not only the lenses, but also their packaging of foil and plastic, which has to be separated to go to recycling plants, said Rick Zultner, director of process and product development for TerraCycle.

"Every waste stream has its unique scratches," he said.

The best ways to dispose of your contact lenses

Bausch + Lomb has a recycling program that allows contact lens wearers to participate in two ways. They can take their used packaging and lenses with them to more than 2,000 participating physicians' practices. Or they can send them directly to the recycling center that works with the company. The user puts his waste in a cardboard box, downloads a preprinted label and sends it out.

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