Lenses Found in Sewage Sludge Nationwide

Crews recover about one pair of contact lenses for every two pounds of sewage sludge from American treatment tanks.

Updated on Nov. 5, 2026 in Environmental

Photograph of a concrete wastewater settling tank with dark sludge and a pair of translucent contact lenses floating near a rusted steel railing. — Crews recover about one pair of contact lenses for every two pounds of sewage sludge from American treatment tanks, researchers at Arizona State University found. AI Illustration. Upload story photo >

Live Poll

Do you ever flush your used contact lenses down the sink or toilet?

Sewage crews find a pair of contact lenses in about every two pounds of sludge from U.S. wastewater treatment tanks. Researchers at Arizona State University found that microbes in treatment plants weaken lens polymers and break them into microplastics.

Why it matters

Soft contact lenses are denser than water and nearly transparent, so they pass through drains and treatment systems unnoticed. Sewage sludge is routinely applied on land for disposal and soil conditioning, which raises questions about where the fragmented plastic ends up.

The study estimates 20 to 23 metric tons of lens plastic enter U.S. wastewater each year, with a lower estimate of 6 to 10 metric tons. Researchers tested 13 contact lens brands made from 9 plastic polymers, and the full environmental impact of the resulting microplastics remains unmeasured.

The players

Arizona State University

A public research university in Tempe, Arizona, which conducted the nationwide study of lens degradation in wastewater.

Centers for Disease Control and Prevention

The federal public health agency whose figure of 45 million American contact lens wearers anchors the scale of the problem.

The details

Researchers exposed five lens polymers to anaerobic and aerobic microorganisms from wastewater treatment plants for varying lengths of time. Lenses survived treatment for extended periods, and microbes altered the lens surface and weakened the polymer until it fragmented.

Lenses are flushed continuously, with an estimated 1.8 to 3.36 billion flushed annually in the U.S.

Big Picture

Using the CDC's count of 45 million American contact lens wearers, the study converts a consumer habit into a measurable wastewater load. That scale places disposable lenses alongside other flushed consumer plastics now tracked in sludge.

Flushing contact lenses sends plastic into the wastewater system instead of the trash, which is the practice the study ties to the estimated 7 to 9 million U.S. people who flush their lenses. Disposing of used lenses in the trash rather than down the drain keeps them out of treatment plants.

The takeaway

Throwing used contact lenses in the trash instead of flushing them keeps this plastic out of sewage. The findings point to a simple household change with a measurable effect on the wastewater stream.