Which beta emitter is considered an internal hazard?

• A. Strontium-90
• B. Tritium
• C. Carbon-14
• D. Uranium-238

Answer: (B)

The key idea is internal exposure: a radioactive substance becomes a part of the body, distributing to tissues and irradiating from inside. Beta emitters vary in how they behave biologically, so which one poses an internal hazard depends on how the isotope is incorporated and distributed.

Tritium stands out because it’s a hydrogen isotope that decays by beta emission and readily forms tritiated water. Once inside the body, it behaves like ordinary water and spreads throughout body fluids, meaning every part of the body can receive irradiation from within. Even though tritium’s beta energy is relatively low, its widespread, internal distribution makes it a classic internal hazard that requires careful control and monitoring.

Strontium-90, carbon-14, and uranium-238 have different internal-hazard profiles. Strontium-90 tends to localize in bone, leading to internal exposure concentrated in bone tissue. Carbon-14, while a beta emitter, is incorporated into organic molecules and can contribute to internal dose, but tritium’s behavior as body water makes its internal hazard particularly characteristic. Uranium-238 is primarily a health concern from its chemical toxicity and its alpha emissions when inhaled or ingested, rather than as a beta internal hazard.