You might want to consider nano particles. I learned about them in chemistry class not to long ago. It honestly sounded very concerning. Apperantly they are even used in foods and can end up in the water supply. They do bring some health risk which haven’t been study too well as its a relatively new field. Some of them have been linked to cancer tho I think. Regulations also seem to be lacking.

I couldn’t find out much about them, which honestly is probably due to my lack of research skills and low frustration tolarence at that time