It turns out that when you take materials that are usually not a problem, and change their surface chemistry, they can become problems. Take carbon, for example. Pencil "lead" is graphite. Not a problem. OTOH, take a look at a bottle of graphite lock lube. It's the same element, in a fine powder form. There are all kinds of warnings on it because it can get into your lungs.
IANAChemist but I think a real chemist would agree that surface chemistry is an exciting new field, and we don't know enough about it. Sometimes you can get exposed to things in weird ways because they're small.
To take an oddball analogy here... jumping up and down on a mile high peak is not a problem. People do it all the time. Now shrink the mountain down to six feet and try jumping up and down on the peak. Ouch.