Changing focus

06 November 2020

Contact lenses have an unusual chemistry.

A study from the US has proposed that disposable contact lenses could be an overlooked source of microplastic pollution.

In a survey, researchers from Arizona State University found that only 0.04% of contact lenses in the US are recycled. Some are disposed of in the bin while others are flushed away. As lenses are made of silicon hydrogels they are denser than water, meaning they could get stuck in sewage sludge during treatment. Researchers estimate that sewage sludge could comprise up to 45 000 kg of contact lenses each year.

Looking into the fate of the contact lenses during the processing of the sludge, the researchers found that they were degrading into smaller particles, pointing out that contact lenses have an unusual chemistry. ‘Contact lenses are soft and porous. We are unsure if this means they will act differently as a pollutant. For example, microplastics are known to adsorb dangerous chemicals at high concentrations.

Perhaps hydrogels can adsorb even higher amounts of these dangerous chemicals,’ said the study’s lead author Charles Rolsky.

The contact lens industry has expressed its concerns about the potential adverse impacts of disposable lenses on the environment and many manufacturers are adopting measures to recycle lenses at a consumer level.

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