The concentration of a radionuclide in air which, if breathed by the reference man for 2,000 hours under light work, results in an intake of one ALI is called what?

• A. DAC
• B. ALI
• C. CEDE
• D. CDE

Answer: (A)

This question hinges on how ALI and DAC relate. ALI (annual limit on intake) is the maximum amount of radioactive material a worker may ingest or inhale in one year. DAC (derived air concentration) is defined as the concentration of a radionuclide in air that would deliver that same ALI to a reference person breathing for a standard workload, which is 2,000 hours per year under light work.

So, the concentration in air that would result in an intake equal to one ALI when breathed for 2,000 hours is the Derived Air Concentration. The other terms refer to dose after intake (committed dose) rather than the air concentration needed to reach the ALI, so they don’t fit this definition.