Although the International System of Units (SI) defines the sievert (Sv) as the unit of equivalent dose, chronic radiation levels and standards are still often given in units of millirems (mrem), where 1 mrem equals 1/1,000 of a rem and 1 rem equals 0.01 Sv. Light radiation sickness begins at about 50–100 rad (0.5–1 gray (Gy), 0.5–1 Sv, 50–100 rem, 50,000–100,000 mrem).
The following table includes some dosages for comparison purposes, using millisieverts (mSv) (one thousandth of a sievert).
Note that 100 mSv is considered twice in the table below â once as received over a 5-year period, and once as an acute dose, received over a short period of time, with differing predicted effects. The table describes doses and their official limits, rather than effects.