4. Conclusions
The present study demonstrated that the protective Al(OH)3 layer present in the SSL formulation may be compromised and leached when in contact with SPW ingredients, especially Ca2+ and OCl− ions, leaving TiO2 nanoparticles un-coated. This could lead to un-wanted and even dangerous photocatalytic activities on human tissues and degradation of chemical compounds (e.g. 35% degradation of p-CBA) and in the environment through free radical formation (e.g. formation rate of 54.7 nM min−1 observed in a current study). However, more detailed analysis of radical production and degradation of target compounds is warranted in the presence of commercial SSL. The findings presented here will provide noteworthy information to the public whether swimming pool water ingredients can compromise the protective layer and expose photoactive nanoparticles, assist in designing SPW-resistant constituents in sunscreens, and promote further research on TiO2 nanoparticles due to the potential mutagenic effects.