Contact lenses end up in the ocean endangering sealife

IMAGE Contact lenses recovered from treated sewage sludge could harm the environment.  view more  Credit Charles Rolsky

IMAGE Contact lenses recovered from treated sewage sludge could harm the environment. view more Credit Charles Rolsky

"They persist during water treatment, they become part of sewage sludge", Prof Rolf Halden, from the Centre for Environmental Health Engineering at Arizona State told BBC News.

A study estimates that between six and ten tonnes of plastic lenses end up in wastewater in the United States alone each year. That's an annual 23 metric tons of plastic lenses.

The Arizona State University study suggests that much of the plastic material then ends up in waste water treatment plants.

So the team set about conducting one. The first part was an anonymous survey of 139 contact-lens wearers and non-wearers.

They found 15-20% of USA users simply flick these fiddly lenses down the drain via the bathroom sink or toilet.

Graduate research assistant Varun Kelkar said: 'We found there were noticeable changes in the bonds of the contact lenses after long term treatment with the plant's microbes'.

Even if the whole contact lens does not escape through waste water filters, the fragments of them can be unsafe, too, contaminating the environment.

Now a research team based in the U.S. has shown for the first time how they can get eaten by fish and other marine life and be returned to us on our plates. To help address their fate during treatment, the researchers exposed five polymers found in many manufacturers' contact lenses to anaerobic and aerobic microorganisms present at wastewater treatment plants for varying times and performed Raman spectroscopy to analyze them.

They found that, even after extended periods of time, the lenses remained intact.

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To address this uncertainty, researchers began by studying 15,428 adults aged 45-64 years from diverse socioeconomic backgrounds. Another important finding of the study is how the source of fat and protein affected mortality risks as well.

Some 4.2million people in the United Kingdom wear contact lenses, and one in five wearers dispose of them through the drainage system instead of with other solid waste - sometimes after just a single day's use.

His team had already been investigating plastic pollution and it was a startling wake-up call when they could not find any relevant studies. These bonds had been slightly, but noticeably weakened, indicating that the lens was on the road to disintegration.

Mr Kelkar said: 'When the plastic loses some of its structural strength, it will break down physically. "This leads to smaller plastic particles which would ultimately lead to the formation of microplastics".

What can be done? Well, now contact lens manufacturers don't include any information on the packaging about how to dispose of the used product.

That would be an incredible place to start, the researchers said.

The authors of the study say that lenses should be recycled where this is possible, but if not they should be disposed of by putting them in with other solid, non-recyclable waste.

"A desirable long-term outcome would be to create lenses from polymers that are fine-tuned to be inert during use but labile and degradable when escaping into the environment". 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.

The researchers are presenting their results today at the 256th National Meeting & Exposition of the American Chemical Society (ACS).

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