Data for: Majority of potable water microplastics are smaller than the 20 µm EU methodology limit for consumable water quality

This dataset provides Raman spectral data for the identification of microplastics (MPs) in potable water, collected from ten brands of polyethylene terephthalate (PET) bottled water and one tap water sample. The data includes Raman spectra in .sgd format (SpectraGryph Spectra File) for all analyzed particles, facilitating reuse for studies focused on MP identification and methodological validation. MP concentrations across the samples varied from 19 to 1,154 particles per liter (n/L), corresponding to 0.001 to 0.250 micrograms per liter (µg/L). While all bottled water samples were stored in PET containers, PET contributed to only a minor fraction of the identified MPs in the majority of cases. A total of 14 different synthetic polymer types were detected, highlighting the diverse composition of microplastics in potable water. Notably, 98% of detected MPs were smaller than 20 µm, and 94% were below 10 µm, emphasizing the critical need to include smaller MPs in potable water assessments and regulatory frameworks.

Methods
In total, n = 660,683 particles were investigated, averaging n = 55,057 particles per sample (~18 thousand particles per 2x2 mm grid subsample), including the procedural blank. All particles measuring ≥1 µm in area-equivalent diameter (circular model) were subject to Raman analysis. Raman measurements were carried out at 20°C using a Horiba LabRAM Soleil (Jobin Yvon, France). The samples were excited at 8% (7.2 mW) power output with a high stability air-cooled He–Cd 532 nm laser diode utilizing a Nikon LV-NUd5 100x objective. The lateral resolution of the unpolarized confocal laser beam was on the order of 1 µm. Spectra were generated in the range of 200–3400 cm−1 using a 600 grooves/cm grating with a 100 µm split. The spectral resolution was on the order of 1 cm−1. Particles within each mosaic, constructed using the LabSpec6 (LS6) SmartView configuration, were analyzed using the Particle Finder application V2. LS6 SmartView determines the topography (± 50 µm) and saves the focal point of all particles on the captured micrograph, enabling the stage to rapidly move the relevant particle into focus. The micrograph is converted into an 8-bit 0–255 greyscale image in which parameters are set by the user to visually separate particles from the darker filter substrate. Each particle was analyzed for 1 s by 2 accumulations at the above-described settings.