Microplastics in bottled water sold in Mexico: Occurrence, polymer composition and human exposure assessment

Mexico is among the world's leading consumers of bottled water per capita; however, comprehensive data on microplastic (MP) contamination across the commercial brands in the country remains limited. In this study, ten widely commercialized bottled water brands (n = 50 samples) were analyzed using membrane filtration, optical microscopy, scanning electron microscopy (SEM), and Fourier-Transform Infrared (FTIR) spectroscopy for polymer identification. A total of 2,358 MP particles were detected in the analyzed samples with an average concentration of 39.3 ± 14.6 particles/L. Fibers were the predominant shape of the detected MPs (72.2%), and transparent particles were the most frequent color (57.7%). Notably, most of detected MPs were smaller than 500 µm (80.3%), raising toxicological concerns due to the high probability of systemic translocation in human tissues. Furthermore, PET and PP polymers were detected among the selected MP particles analyzed by FTIR spectroscopy. The estimated intake assessment revealed that children experience the highest exposure on a body weight basis (228.2 particles/kg/year), followed by adults (158.3 particles/kg/year) and youth (148.3 particles/kg/year). These findings provide robust evidence of MP contamination in bottled water sold in Mexico and highlight bottled water consumption as a potential pathway of human exposure.