Nanopore protein (α-hemolysin) was used to detect sub-nanosized plastic particles leached from a PE-coated paper cup. These sub-nanosized plastic particles can increase the inflammation response of macrophages. Display omitted •Nanopore sensing detects sub-nanosized plastics in PE-coated paper cups.•Sub-nanosized plastic particles in paper cups were 1.8 times more detected in boiled water than in room temperature water.•Sub-nanosized and microplastic particles alter cell membrane dynamics.•Sub-nanosized plastic particles can induce inflammatory cell responses. In recent years, there has been growing global concern about environmental pollution, and the increasing use of plastic products has made microplastics a serious environmental pollutant worldwide. Accordingly, the development of microplastic detection methods and research on the harmful effects of microplastics on human health are being actively pursued. In this study, we detected particle leaching from PE-coated paper cups using label-free nanopore sensing to identify and quantify the presence of sub-nanosized plastic particles. Plastic particles leached from the paper cups were classified as < 1 nm and > 1 nm, and their interactions with artificial cell membranes and inflammatory responses in the cells were evaluated. The results demonstrated that in a commonly used paper cup, particles < 1.4 nm were present at a concentration of approximately 1.13 mM in hot water and 0.62 mM in room-temperature water. It was demonstrated that plastic particles < 1 nm could condense the artificial cell membrane, whereas particles > 1 nm could thicken the artificial cell membrane. Furthermore, both size ranges of particles leached from the paper cups triggered an inflammatory response in the cells, with the inflammatory response increasing in proportion to the concentration and treatment time. The detection and analysis revealed the presence of sub-nanosized plastic particles in PE-coated paper cups, which are commonly used in daily life. These particles pose health threats and contribute to environmental pollution.