Are there pico(nano)-plastics in a polyethylene coated paper cup?

Abstract

As problems associated with microplastics that may be harmful to the human body continue to emerge, various eco-friendly materials are being used as alternatives to plastic. One of them is to use paper cups instead of plastic cups. However, they cannot be used without water-proof coating since paper cups do not have water-proof capability. Therefore, polyethylene (PE) is mainly used as a coating material. However, there are some issues with some of the polyethylene coating that may come off and dissolve when exposed to liquid. Currently, many studies have shown that nano/microplastics in several tens of nanometers are present and many of their potential risks have been studied. However, microplastics in smaller sizes have yet to be clarified, precluding the further investigation of their effects or potential risks. If there were nanoplastics in several tens of nanometers, these would not be detected because they were difficult to measure with general instruments. In this study, a lipid bilayer and pore proteins were used to detect pico/nanometer-size plastics in PE-coated paper cups. These were measured by changes in current as they passed through the pores, and plastics smaller than the pore size was detected when they pass through the pore protein or interfere with the ion current. We also found that some particles could block the pore. Not only paper cups containing hot water, but also that containing water in room temperature were detected in a smaller frequency. Because of their hydrophobic properties, they can be inserted directly into the hydrophobic region of cell membrane, and potentially passing through channel proteins, such as ion channels, or blocking the channel proteins, resulting in dysfunction and cell death.