I’ve seen these in quite a few photos, always at night, but am not sure what they are. Is this moisture in the air, an artifact of light or something else?
It would be interesting to set a digital camera on a tripod at night, take two consecutive shots using the flash and compare them. This would determine if it is indeed something in the air or dust/moisture on the lens.
It most of those pictures, there appears to be different sizes of specks at different levels of brightness, indicating dust particles in the air.
If you were to take multiple pictures from a tripod, as long as the subject isn’t moving and the particles are moving, you could remove the particles with this cool technique in Photoshop.