Which of the following is NOT a listed reason why internal radioactive material can be more serious than external?

• A. It provides 24/7 exposure
• B. It can concentrate in certain body organs
• C. It can be easily detected by external surveys
• D. It can be difficult to detect and assign dose

Answer: (C)

Internal radioactive material is more dangerous because once it’s inside the body it irradiates from within, providing exposure continuously as long as it remains there. This means the dose isn’t easily stopped by shielding or distance, and it can spread through the body over time as the radionuclide decays and is transported to different tissues.

Additionally, internal contamination can concentrate in specific organs, making those organs receive a higher dose than the rest of the body. This organ-specific uptake can lead to targeted damage and health risks that external exposure might not cause as acutely.

Estimating the actual dose from internal contamination is also more complex. It requires understanding how the substance is taken into the body, how it moves and clears from different tissues, and how it decays—information that often needs specialized monitoring and calculations rather than simple external measurements.

The statement that it can be easily detected by external surveys is not a listed reason why internal contamination is more serious. External surveys may miss internal contamination or fail to quantify the true internal dose, so they do not reflect the internal risk accurately.