Current Status of Organic Matters in Bottled Drinking Water in Korea

Microplastics may be ubiquitous across ecosystems, yet the current state of exposure to microplastics in daily life remains poorly understood. We focused on drinking water in plastic bottles purchased from a local market in South Korea. The composition, amount, and size of organic matter in solid residues obtained by freeze-drying drinking water in a plastic bottle were determined using analytical methods including dry ashing, centrifugation, Raman analysis, and electron microscopy. A significant amount of organic matter was found in the plastic bottles (0.25-2.0 mg/L), and once the organic matter was concentrated and dried as a solid, it was not soluble in water. In addition, a series of stress to the plastic bottle, such as light, heat, and mechanical stress, did not significantly increase the organic matter within a month. The potential adverse effects of organic matter on humans were evaluated using the human intestinal Caco-2 cell line. The results showed no significant toxicity in cell viability even at relatively high concentrations of organic matter (1.0 mg/mL). However, the monitoring of the accumulation of organic matter in the human body over a longer period of time will be needed because of the higher probability of nanoscale material uptake in the long term.