“…The toxicity of metal nanoparticles and, especially, of metal oxide ones (MeO-NPs) has been a subject of extensive studies conducted by our team for the last few years [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. Apart from a range of purposely manufactured (“engineered”) NPs, very important are their “natural” analogues always present in the workplace and ambient air of arc-welding and metallurgical operations.…”