Release of microplastics from commonly used plastic containers: Combined meta-analysis and case study

Daily ingestion of microplastics (MPs) is a growing public-health concern, partially linked to widespread use of single use of plastic cups and containers. However, the roles of temperature, polymer, container (or cup) material, and soaking time in MP release remain poorly understood. We conducted a meta-analysis of 237 observations from 30 peer-reviewed studies, alongside an experimental case study comparing microplastic release from polyethylene (PE) cups and PE-coated paper cups. The meta-analysis revealed that MP release from products made of PE, polyethylene terephthalate (PET), polypropylene (PP), and polystyrene (PS) significantly increased with temperature, though the extent varied significantly, depending on the type of polymer, ranging from hundreds to over eight million particles. Soaking time, by contrast, did not significantly affect MP release. The case study showed that PE-coated paper cups consistently released fewer MPs than PE plastic cups at both 5 °C and 60 °C. Specifically, MP release from PE cups increased by 32.7 % when the temperature rose from 5 °C to 60 °C, a trend not observed in the PE-coated paper cups. Surface analysis revealed that PE cups had higher surface and peak-to-valley roughness, which may account for greater MP shedding. Collectively, the results from both the meta-analysis and case study highlight that temperature-induced physical degradation, especially in polymers with rougher surfaces or lower thermal stability, is a key driver of microplastic release, and that material design plays a critical role in mitigating this effect. These findings offer practical insights for reducing microplastic exposure through material selection and support future regulatory efforts aimed at safer consumer packaging.