Six commercial sunscreens were selected based on product
descriptions and promotion flyers mentioning the presence of
inorganic NPs in their formulation. Table 1 lists inorganic ingredients
and their amounts in the cosmetics. Among these
sunscreens, two contained only TiO2, two contained only ZnO,
and two contained a combination of TiO2 and ZnO. All sunscreens
were obtained without prescription; one product was
made in Korea, one in France, and the others were produced in
the USA. Standard solutions of TiO2 (107 nm) and ZnO NPs
(76 nm) used as control samples were purchased from SigmaeAldrich
(St Louis, MO, USA). The TiO2 NP standard solution
consisted of anatase and rutile crystals.