Researchers have called on contact lens (CL) companies to address the way CLs are disposed of, advising wearers to put used CLs with other solid plastic waste.
It is estimated that around 15 to 20 per cent of America’s 45 million CL wearers flush their lenses down the sink or toilet. As a result, anywhere from six to 10 metric tons of plastic CLs end up in US wastewater treatment plants.
Because CLs are unlike other plastic waste (often made with a combination of polymethylmethacrylate, silicones, and fluoropolymers), the effect of wastewater treatment on CLs was unknown.
Professor Rolf Halden and colleagues from Arizona State University set out to determine how CLs break down and whether they pose a threat to aquatic life. They exposed five polymers found in many CLs to anaerobic and aerobic microorganisms present at wastewater treatment plants for varying times.
They reported, “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… Aquatic organisms can mistake microplastics for food and since plastics are indigestible, this dramatically affects the marine animals’ digestive system. These animals are part of a long food chain. Some eventually find their way to the human food supply, which could lead to unwanted human exposures to plastic contaminants and pollutants that stick to the surfaces of the plastics.”