Which dose value corresponds to the dose at which deleterious effects can be observed in embryo/fetus?

• A. 10
• B. 5
• C. 25
• D. 50

Answer: (A)

Deterministic fetal effects from radiation have a threshold: below a certain dose, observable harm is unlikely, and above it, effects such as congenital anomalies or neurodevelopmental issues can occur depending on the timing of exposure. The threshold for observable fetal harm is about 0.1 Gy (100 mGy). If the options are in rad, 10 rad equals 0.1 Gy, marking the dose at which deleterious effects can first be observed. Lower doses, like 5 rad, are below the threshold and unlikely to cause observable harm, while higher doses (25 rad, 50 rad) would exceed the threshold and could produce effects.