Microplastic release from PET-packaged beverages and acidic condiments: Effects of storage time and environmental conditions

Background Although microplastics (MPs) have been detected in bottled beverages, the combined effects of beverage composition, prolonged storage, and environmental conditions on MP release from PET containers remain insufficiently characterized. This study addressed this gap by systematically evaluating MP abundance and size distribution across diverse beverage matrices under multiple storage conditions over an eight-month period. Methods Nine PET-bottled beverages and acidic liquid condiments, including vinegar, sour lemon juice, sour grape juice, soda, non-alcoholic beer, fruit juice, carbonated fruit drink, mineral water, and carbonated water, were evaluated. Samples were stored under outdoor exposure, 25 °C, 45 °C, and 4 °C conditions, with MP measurements performed at two-month intervals. MPs >10 µm were quantified, characterized by size, and representative particles were analyzed using SEM–EDX and Raman spectroscopy. Two-way ANOVA was used to evaluate the effects of storage time, storage condition, and their interaction. Estimated daily intake (EDI) was calculated for adults and children. Results MP concentrations increased progressively during storage, ranging from 98 to 36,093 particles/L. At baseline, sour lemon juice showed the highest concentration (184 ± 48 particles/L), while non-alcoholic beer had the lowest (98 ± 28 particles/L). By month 8, sour grape juice and sour lemon juice reached mean concentrations of 14,703 ± 14,909 and 14,347 ± 13,564 particles/L, respectively. Storage time, storage condition, and their interaction significantly affected MP levels across all beverage categories (P < 0.0001). Storage time was the dominant factor in acidic beverages (η² = 40.89–44.25%), whereas storage condition predominated in most other beverages (η² = 41.44–62.72%). Outdoor exposure and 45 °C consistently promoted greater MP release, while 4 °C minimized release. Maximum EDI reached 37.16 MPs/kg·day in adults and 80.70 MPs/kg·day in children for carbonated fruit drinks. Conclusions MP release from PET-bottled beverages is strongly dependent on both beverage matrix and storage environment, with prolonged storage particularly important for acidic products and environmental stressors more influential in several non-acidic beverages. These findings provide practical evidence supporting cooler storage and reduced prolonged exposure of PET-bottled beverages to heat and outdoor conditions as potential strategies to limit MP release and dietary exposure.