Plutonium existing in the environment is mostly in the form of microscopic dust particles of plutonium-239, mainly from the remnants of nuclear weapons testing and nuclear reactor accidents. Plutonium-238 however-the kind used in batteries to power satellites-is much more radioactive. Radioactive decay is usually in the form of alpha particles, but plutonium decay does release gamma radiation as well. Alpha particles lose energy very quickly so ingesting radioactive atoms through breathing or from cuts are the primary way this type of radiation affects the body. Gamma radiation can travel longer distances and are typically deflected or reduced with thick concrete walls, water or lead.
So what would happen if you ingest radioactive atoms in the most dangerous way, by inhaling them? Plutonium particles lodge in the lungs (diagram 1), killing the cells causing scarring and an increased potential for lung disease and cancer. But it doesn't stop there. It can enter the bloodstream (diagram 2) and travel to the kidneys (diagram 2) doing even more damage and increased cancer risk. Once in the body, it tends to settle in the bones (diagram 3), liver (diagram 3) and spleen (diagram 3) continuing to increase the opportunities for cancer. Since plutonium-238's half-life is a little more than the average human lifespan, 87.7 years, it stays around a while. On the other hand, because the half life is low (as compared to plutonium-239 with a half life of 24,110 years), it is more radioactive and dangerous. Plutonium that is eaten via contaminated food or water is not absorbed as easily by the digestive system and tends to pass through the body.
Radiation, measured in units called a rem (Roentgen Equivalent in Man), affects people in different ways. Most people receive about three-tenths of a rem per year due to naturally produced radiation, mostly from radon. In a group of 10,000 people, if each person were exposed to one rem of radiation, the increased deaths as a result of the exposure would be five or six individuals. An exposure of 50 rems would typically result in nausea, while 400 rems typically results in death. For comparison, people in the city of Chernobyl, Russia, were exposed to about 45 rems from the nuclear reactor accident in 1986.
Source: Center for Disease Control Emergency Preparedness & Response radioisotope brief on plutonium.