SEM images of the baby bottle material after being treated with water (Fig 2A-1) and acetic acid (Fig 2A-2) at 70 c for 2 h confirmed previous observations. In both images, silver particles with amorphous structure and size ranging between 300 to 900 nm were observed. In addition, nanocrystals of CaCo3 and Na2CO3 were detected in the polymer surface, as confirmed by EDX analyses (Fig 2E and F). SEM image of the food box material treated with 3% acetic acid (Fig 2B-1) showed a translucent body that lied in the internal part of the material and contained silver (Fig 2G). However, it was not possible to determine whether silver was present as a NP or as an agglomerate.