What health risk is associated with a 1000 mrem occupational dose?

• A. An immediate life-threatening event.
• B. No risk.
• C. A 2% increased risk of all cancers.
• D. An increase in the risk of contracting fatal cancer by 0.04 percent.

Answer: (D)

Low-dose radiation exposure carries a probabilistic, not immediate, health effect. A dose of 1000 mrem (which is 1 rem or 10 mSv, i.e., 0.01 Sv) adds only a tiny risk of harm over a lifetime. Using a common risk coefficient for fatal cancer of about 5% per Sv, the additional risk from 0.01 Sv is roughly 0.05%, which rounds to about 0.04% in many practical estimates. So there is a small but real increase in the chance of fatal cancer, not an immediate threat or a zero-risk situation. This is why the statement describing a small increase in fatal cancer risk, around 0.04%, best fits the dose.