Which statement correctly describes the use of ALI and DAC together in dose planning?

• A. ALI sets the maximum yearly intake, and DAC provides an air concentration corresponding to a yearly dose, together with exposure duration and breathing rate, they determine safe limits.
• B. ALI is unrelated to intake limits.
• C. DAC is used to estimate shielding thickness.
• D. ALI and DAC are not used in dose planning.

Answer: (A)

The key idea is that ALI and DAC connect intake safety to workplace air levels. The annual limit on intake defines how much radioactive material a worker can ingest, inhale, or absorb in a year without exceeding dose limits. The Derived Air Concentration translates that same limit into an air concentration value: the amount of activity in each cubic meter of air that would deliver the ALI if the worker breathes at a given rate for a certain exposure time. In dose planning you use ALI together with DAC, along with how long the exposure lasts and how much air the person breathes, to determine whether the planned work will stay within safe limits and to set practical controls (like ventilation, job duration, or protective equipment). The other statements aren’t accurate because ALI is indeed an intake limit, DAC isn’t used to estimate shielding thickness, and ALI and DAC are central to dose planning.