Which statement correctly defines Derived Air Concentration (DAC) and Annual Limit on Intake (ALI)?

• A. DAC is the concentration in air that would deliver a specified dose; ALI is the maximum annual intake allowed given exposure conditions.
• B. DAC is the rate of air contamination; ALI is the annual limit on inhalations.
• C. DAC is the concentration in water; ALI is the annual limit on intake by ingestion.
• D. DAC is the maximum dose allowed in air; ALI is the average intake per year.

Answer: (A)

Derived Air Concentration is the concentration of a radionuclide in air that would deliver a specified committed dose to a worker if that air is inhaled under the defined exposure conditions. The annual limit on intake is the maximum activity a worker may ingest or inhale in one year without exceeding regulatory dose limits. These two concepts are connected by how much air a person breathes in a year: DAC equals ALI divided by the annual inhaled air volume (breathing rate times time). This converts a dose-based limit into an air concentration used for monitoring and control.