Can anyone tell whether these exposures occurred through the camera lens (from fallout particles in the sky of the depicted scenes) or in post- (or pre-) exposure handling of the film from hot dust carried by the photographer?

Also the sobering footage taken by this YouTuber by sending a GoPro through a particle accelerator: https://www.youtube.com/watch?v=Uf4Ux4SlyT4

thank you so much for this link! I have been trying to search for footage of this phenomenon (in the pre-llm era) 10+y ago