The half-life of ^235^U is hundreds of millions of years so it is not a concern. However, it will literally become a nuke if too much (a few liters or 60 kg) get too close together.

The half-life of plutonium-239 is tens of thousands of years so only a thousandth will get a chance to hurt Theodore over his lifetime. However, it is probably chemically toxic so it might cause non-radiation poisoning.

Radium-225 will decay in days, and will quickly go through 7 more radioactive reactions, both alpha and beta, before becoming essentially stable bismuth. It is the worst by far.

The plutonium gives off some alpha radiation that won’t hurt you if you don’t eat it.

Breathing in particles of plutonium is the danger.

Because it emits alpha particles, plutonium is most dangerous when inhaled. When plutonium particles are inhaled, they lodge in the lung tissue. The alpha particles can kill lung cells, which causes scarring of the lungs, leading to further lung disease and cancer. Plutonium can enter the blood stream from the lungs and travel to the kidneys, meaning that the blood and the kidneys will be exposed to alpha particles. Once plutonium circulates through the body, it concentrates in the bones, liver, and spleen, exposing these organs to alpha particles. Plutonium that is ingested from contaminated food or water does not pose a serious threat to humans because the stomach does not absorb plutonium easily and so it passes out of the body in the feces.

Radioisotope Brief: Plutonium