Physical and Chemical Characterisation of Ophthalmic Lenses Grinding Wastewater: Uncovering Environmental Implications

<title>Abstract</title> The ophthalmic industry's eyewear lens production generates substantial waste during the lens grinding processes, contributing to significant environmental challenges. This process consumes approximately 20 litres of water per eyeglass lens pair, which is subsequently discharged directly into wastewater systems, releasing a complex mixture of pollutants, including micro and nanoplastics, into the environment. It is important to identify the quantity and nature of this neglected waste stream to determine whether it contributes significantly to plastic pollution and releases hazardous contaminants. This requires detailed characterisation. For this purpose, this study investigates the wastewater generated by lens grinding machines in opticians and provides a detailed physical and chemical characterisation of this waste stream. The results revealed a significant material loss during grinding, with approximately 50% of each initial lens mass being discharged during cutting. Based on conservative estimates, 11.6 million lenses are ground annually, representing an estimate of 5,800 tonnes of plastic waste released into the environment each year.A variety of hazardous contaminants, including particles below 2 µm, heavy metals, bisphenol A, phthalates, and fluorinated compounds, were also identified. The presence of these substances raises significant concerns as they are known endocrine-disrupting chemicals and persistent organic pollutants, posing a significant risk to aquatic ecosystems and human health.This study provides new, valuable information to alert the opticians, competent authorities, policy makers, and society to developing future policies and alternative materials and waste management strategies within the ophthalmic industry.