In the context of radiation safety, the effective dose to a radiation worker from occupational exposure is limited to 20 mSv per year averaged over 5 years, with no single year exceeding 50 mSv. Which unit correctly represents the SI unit for radiation absorbed dose AND the unit for effective dose (accounting for tissue weighting factors)?

• A Becquerel (Bq) for absorbed dose; Sievert (Sv) for effective dose
• B Rad for absorbed dose; Rem for effective dose
• C Gray (Gy) for absorbed dose; Sievert (Sv) for effective dose ✓
• D Curie (Ci) for absorbed dose; Gray (Gy) for effective dose

Explanation

In SI units: Gray (Gy) is the unit of absorbed dose (1 Gy = 1 J/kg of energy absorbed). Sievert (Sv) is the unit of effective dose, which is calculated by multiplying the absorbed dose in each tissue/organ by the radiation weighting factor (Wr) and then the tissue weighting factor (Wt) — effectively converting physical energy deposition into a biological risk-equivalent measure. Becquerel (Bq) measures radioactivity (disintegrations per second). Curie (Ci) is the older non-SI unit of radioactivity. Rad and Rem are older non-SI units (1 Gy = 100 rad; 1 Sv = 100 rem).

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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