Which phrase best defines ALARA?

• A. As Low As Realistic Achievable
• B. As Low As Readily Achievable
• C. As Low As Reasonably Achievable
• D. As Low As Regulated And Authorized

Answer: (C)

The main idea here is optimizing protection by reducing exposure to the lowest level that can be realistically achieved. The best definition is “As Low As Reasonably Achievable.” This phrase captures the balance between dose reduction and practicality—the effort, cost, technology, and social factors involved in making that reduction. It means you should continuously pursue ways to lower exposure, but only if the additional effort or cost is reasonable compared with the dose savings.

Why this fits best: ALARA isn’t about zero exposure or simply what’s easy to do; it’s an ongoing optimization. You apply protective measures (engineering controls, administrative controls, PPE, work practices) and keep improving them as new options become available, stopping when further reductions would be disproportionately costly or impractical.

The other phrases don’t fit that balancing act. They imply constraints like realism, ease, or regulatory authorization rather than the broader optimization principle that weighs benefit against effort and resources.