What unit is commonly used to express the annual effective dose from natural background radiation?

What unit is commonly used to express the annual effective dose from natural background radiation?

• A. mSv
• B. Sv
• C. rem
• D. Gy

Answer: (A)

The main idea is that the annual effective dose expresses biological risk using the Sievert scale, which already accounts for the type of radiation and the sensitivity of tissues. For natural background, the numbers are small—only a few millisieverts per year—so using millisieverts keeps the values practical and easy to compare. Gray measures the absorbed dose (energy per mass) and doesn’t reflect the different biological effects. Rem is an older unit (1 Sv = 100 rem), but the modern standard is the SI unit Sievert, typically expressed in milli- or micro-sieverts for background levels. Gy and the absorbed-dose concept don’t convey the overall biological risk by themselves. Hence, millisieverts is the most appropriate unit for annual background radiation doses.

The main idea is that the annual effective dose expresses biological risk using the Sievert scale, which already accounts for the type of radiation and the sensitivity of tissues. For natural background, the numbers are small—only a few millisieverts per year—so using millisieverts keeps the values practical and easy to compare. Gray measures the absorbed dose (energy per mass) and doesn’t reflect the different biological effects. Rem is an older unit (1 Sv = 100 rem), but the modern standard is the SI unit Sievert, typically expressed in milli- or micro-sieverts for background levels. Gy and the absorbed-dose concept don’t convey the overall biological risk by themselves. Hence, millisieverts is the most appropriate unit for annual background radiation doses.