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How are gray and sievert units used to describe radiation exposure?

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The environmental effects of nuclear radiation — radiation The harmful effects of radiation from nuclear bombing.

In physics, the gray and sievert are both units of the International System of Units (SI) used to measure radiation exposure, but they serve distinct purposes.12

The Gray (Gy)

The gray measures the absorbed dose of ionizing radiation. It is defined as the amount of energy deposited per unit mass of matter, specifically one joule per kilogram. It quantifies the physical energy absorbed by tissue but does not account for the biological impact of different radiation types.13

The Sievert (Sv)

The sievert measures the dose equivalent, which accounts for the biological impact of radiation on living tissue. Because different types of radiation (such as neutrons versus gamma rays) cause varying levels of damage, the sievert is calculated by multiplying the absorbed dose in grays by a quality factor based on the radiation's relative biological effectiveness (RBE).23

Essentially, one sievert represents the amount of radiation that is biologically equivalent to one gray of gamma radiation. Due to the large size of these units, the millisievert (mSv) is frequently used for practical applications.23