effective half life

https://doi.org/10.1351/goldbook.E01894
For a
radioactive
substance, the time required for the amount of that substance in a biological system to be reduced to one half of its value by both
radioactive decay
and biological processes, when the rate of removal is approximately exponential.
Source:
PAC, 1994, 66, 2513. (Nomenclature for radioanalytical chemistry (IUPAC Recommendations 1994)) on page 2520 [Terms] [Paper]