Radioactive material is eliminated from the body by which process?

• A. Decay—Naturally Occurring Over Time
• B. Biological excretion via fecal material/urine
• C. External shielding
• D. Chemical binding to tissues

Answer: (A)

Radioactive material inside the body loses activity mainly because the unstable nuclei themselves transform into stable forms over time. This natural decay reduces the amount of radioactivity regardless of what the body does to clear the substance. The rate of this reduction is defined by the isotope’s half-life, so even if some material is cleared by the body, the intrinsic decay process is what continually lowers the radioactive burden.

Biological excretion via urine or feces can help remove material from the body faster in some cases, but it doesn’t cause the radioactivity to disappear on its own—the decay process does. External shielding doesn’t remove material from the body at all; it only protects others from radiation. Binding to tissues would tend to keep the material around rather than eliminate it.

So, the best answer is that the radioactive material is eliminated from the body by decay occurring naturally over time.