Bioassay is performed to measure which of the following?

• A. The monitoring of environmental contamination in air
• B. The calibration of dosimeters
• C. The measurement of surface contamination
• D. The measurement of radionuclide content in the body or excreta to assess intake and dose

Answer: (D)

Bioassay is used to determine internal contamination by measuring radioactive material inside the body or in excreta, which is essential for estimating intake and the resulting dose. This falls under internal dosimetry: after potential ingestion or inhalation of radionuclides, we quantify how much radionuclide is present in the body, often through in vivo measurements (like whole-body or organ-specific counting) or through analysis of urine or feces. From that body burden we estimate the committed dose to assess health risk and guide medical or regulatory actions.

Environmental monitoring in air looks for contamination in the environment, not inside a person. Calibrating dosimeters is about ensuring instruments read radiation accurately, not about measuring internal radionuclide content. Surface contamination measurements focus on radioactive material on surfaces, not on the body's internal burden.