Abstract
Kinetics of the cumulated activity in human body determines strongly medical impacts of ionizing radiation. The effective half-life is mostly used as its global descriptor.
The effective half-life was found, however, of a limited use as the underlying deterministic relationship time - activity can hardly be taken as (mono)exponential. More complex dependences of activity on time are inspected here.
While retaining practical feasibility, a substantial descriptive capability is gained as demonstrated on an extensive set of real data.