Ugly ducklings—the dark side of plastic materials in contact with potable water

Visualization of biofilms on the inner surface of bath toys. a The inner surface of a bath toy used under real conditions. b Optical coherence tomography image of the biofilm structure and thickness of the same bath toy (scale bar: 50？μm). c Scanning electron microscopy image revealing the complex structure and composition of these bath toy biofilms. Colors were added artificially to draw attention to varied structures (scale bar: 2？μm). For additional images, see supplementary informatio