‘Dust motes' is all that I can think of. In the Doctor Who universe, it is referred as the swarming, carnivorous being Vashta Nerada (lit. “the shadows that melt the flesh”), said to be seen as the specks of dust visible in bright sunlight.
In Danish, it is called støvfnug (“dust flakes”). (from ehjorth)
Historically the term is “atoms” but that’s before the whole “atoms” thing became associated with what we know today as atoms. So it’s an archaic term now, but still fun to use. (from huckly)
atom, n.: “Each of the particles of dust rendered visible by light; a mote in a sunbeam. arch. and poet. in later use.”
1538 T. Elyot Dict. at cited word, Atomi, be motes of the sonne.
1588 J. Harvey Discoursiue Probl. conc. Prophesies 96 Cabalisticall coiners, and impostural wringers, making at their own pleasure..bodies of Atomes, or sun motes, something of nothing.
1911 W. D. Foulke Maya iii. iii. 56 And he clutched the ray that glittered With its countless atoms floating In the pathway of the sunbeam.
(Oxford English Dictionary)