What happens when you breathe in radioactivity? Does the size of dust particles contaminated with radioactivity matter?

When a person inhales airborne radioactive particles, the particle size determines what fraction of them is deposited in the respiratory tract, and where, and what fraction is exhaled. Some deposited particles may be transported to the throat, swallowed, then leave the body in the faeces. Some may be transported to the lymph nodes. Some are removed as nose blows. If the particles are soluble, some of the radioactive material will dissolve while they are within the body and will be transferred to other organs. It may then be excreted from the body. The degree of solubility of the particles, and other factors, will determine the pathways in the body taken by the radioactive material and its rate of transfer. The risk to the person is from the radiation emitted from the radioactive substance while it remains within the body. In these ways, particle size and solubility will affect the exposure of a person to radiation following inhalation of airborne radioactive particles.