Underpinning ALARA philosophy are the following assumptions: 1) there is no minimum threshold for radiation dose necessary to achieve a biological effect 2) all radiation doses be kept as far below legal limits as possible 3) even the lowest radiation dose is assumed to result in some effect.

• A. 1 and 2
• B. 1 and 3
• C. 2 and 3
• D. 1, 2, and 3

Answer: (D)

ALARA is about reducing radiation exposure as much as reasonably achievable because any exposure carries some risk, and there isn’t a dose that’s known to be completely risk-free. The idea that there is no minimum threshold for a biological effect reflects that even very small doses may have some impact, so we continuously seek ways to lower dose. Keeping all exposures well below legal limits embodies the practical actions taken to minimize risk, using shielding, time, distance, and optimized protocols to push doses down as far as reasonably possible. And the belief that the smallest dose can still produce some effect reinforces why we don’t rely on a safety margin of zero exposure; we actively minimize dose in every situation. Put together, these ideas are all consistent with ALARA, so the best answer includes all of them.