Distribution, Polymer Composition, and Exposure Risks of Microplastics in Bottled and Tap Water Distribution

Microplastic (MP) pollution in bottled and tap water poses escalating environmental and public health challenges due to MPs' capacity to act as vectors for toxicants and pathogens. This study constitutes the first comprehensive evaluation of MPs in drinking water from Madeira Island, integrating detailed chemical and morphological characterisations alongside human exposure estimations. A total of 22 samples, comprising 10 bottled (four mineral, six flavoured) and 12 tap waters, were analysed via stereomicroscopy and micro-Fourier transform infrared (µ-FTIR) spectroscopy. Of the 428 particles detected, 65 were confirmed MPs, 223 were non-plastics, and 140 were indeterminate. Bottled waters were predominantly contaminated by polyethylene terephthalate (PET), polypropylene (PP), and polyethylene (PE), whereas tap waters exhibited a notable presence of PE, PP, polyester, and polyamide (PA). MPs predominantly measured under 400 µm and were transparent; fragments were the main form in bottled water, contrasting with fibres dominating tap waters. Concentrations ranged from 0.5 to 6 MPs/L, with flavoured waters exhibiting the highest average levels (2.00 ± 1.83 MPs/L), followed by tap (1.30 ± 0.80 MPs/L) and mineral waters (0.59 ± 0.37 MPs/L). Estimated daily intake (EDI) spanned 0.01-0.19 MPs/kg/day for adults and 0.05-0.68 MPs/kg/day for children, the latter exhibiting a 3.6-fold greater exposure. Although concentrations were lower than those in many global reports, the ubiquity of MPs underscores the critical need for standardised monitoring protocols, enhanced production standards, and rigorous risk assessments addressing chronic low-level human exposure, especially in insular environments.