Internal exposure results when radionuclides enter the body through inhalation, ingestion, or dermal pathways. Which entry routes are included?

• A. Inhalation
• B. Ingestion
• C. Dermal
• D. All of the above

Answer: (D)

Internal exposure means the radiation dose comes from radionuclides that are inside the body. Radionuclides can enter the body through multiple pathways: breathing them in (inhalation), swallowing them (ingestion), or through the skin (dermal uptake) if contamination is absorbed or if there are wounds. Inhalation deposits material in the lungs and can be absorbed into the bloodstream; ingestion introduces material to the gastrointestinal tract where it can be absorbed systemically; dermal absorption is possible for certain soluble substances or through damaged skin, contributing to internal dose. Because all three routes can lead to internal exposure, the correct choice is all of the above.