Most of the people depend on contact lenses to improve their vision. But these sight-correcting devices don’t last forever – some of these devices are used for a short period of one day and are disposed in various ways. Researches show that throwing these lenses down the drain after usage will contribute to microplastic pollution in waterways.
- A team of researchers presented their results at the 256th National Meeting & Exposition of the American Chemical Society.
- They started looking into the U.S. market and conducted a survey of contact lens wearers. They found that 15 to 20 percent of contact wearers are flushing the lenses down the sink or toilet. This is a pretty large number, considering roughly 45 million people in the U.S. alone wear contact lenses.
- When the lenses are washed down the drain, they ultimately end up in wastewater treatment plants. The team estimates that anywhere from six to 10 metric tons of plastic lenses end up in wastewater in the U.S. alone each year. Contact lenses tend to be denser than water, which means they sink, and this could eventually pose a danger to aquatic life, especially bottom feeders that may ingest the contact lenses.
- Analyzing what happens to these lenses is a challenge for several reasons. First, contact lenses are transparent, which makes them difficult to observe in the complicated setting of a wastewater treatment plant. Further, the plastics used in contact lenses are different from other plastic waste, such as polypropylene, which can be found in everything from car batteries to textiles. Contact lenses are instead frequently made with a combination of poly(methylmethacrylate), silicones and fluoropolymers to create a softer material that allows oxygen to pass through the lens to the eye. So, it’s unclear how wastewater treatment affects contacts.
- These differences make processing contact lenses in wastewater plants a challenge. 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 there were noticeable changes in the bonds of the contact lenses after long-term treatment with the plant’s microbes. The team concluded that microbes in the wastewater treatment facility actually altered the surface of the contact lenses, weakening the bonds in the plastic polymers.
- “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”, says Kelkhar one of the researchers. 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 finally find their way to the human food supply, which could lead to surplus human exposures to plastic impurities and pollutants that stick to the surfaces of the plastics.
- With this research, the team hopes that industry will take note and at minimum, provide a label on the packaging describing how to properly dispose the contact lenses, which is by placing them with other solid waste. The researchers mention that, “Ultimately, we hope that manufacturers will conduct more research on how the lenses impact aquatic life and how fast the lenses degrade in a marine environment.”