To avoid overestimation of microplastics released from actual usage of disposable cups: In-depth quantitative analysis of microplastics and simultaneously exposed chemicals

Abstract

The use of disposable plastic cups has increased because they are sanitary and easy to use. Microplastics (MPs) from plastic products occur extensively in the environment and threaten human health. Measuring and quantifying MP release under various exposure conditions using micro-Fourier-transform infrared spectroscopy is controversial. This study simulated MP release under actual usage exposure conditions. The cups were exposed to 100 mL of liquid simulants (deionized water and coffee) at 20, 60, and 100 °C for 0.5, 1.0, 2.0, and 3.0 h. Contrary to previous studies, lower amounts of polythene-MPs (1–40 particles/100 mL) were released at 100 °C and comparable amounts in the coffee simulants; unexpectedly, glycol monooleate migrated in 10-fold higher amounts. The MP release mechanism was examined based on surface roughness and contact angle changes, which support polyethylene film fragmentation. The most important factor for MPs release was exposure time, while temperature of the liquid simulant was the critical factor for plasticizer (GMO) migration. PE-MP release and migration of the plasticizer (glycerol monooleate) smoothed the rough surface, making the hydrophobic surface more hydrophilic.