Final answer:
High-level radiation exposure is defined as whole-body, single-exposure doses exceeding 1 sievert (Sv), which is equivalent to 100 rem. Doses below this threshold are categorized as low or moderate.
Step-by-step explanation:
What amount of radiation exposure constitutes a high-level exposure? In terms of radiation units, whole-body, single-exposure doses that exceed 1 sievert (Sv) are considered high doses of radiation. To put this into perspective, 1 Sv is equivalent to 100 rem. For clarity, doses of 0.1 Sv or less are categorized as low, while those between 0.1 to 1 Sv are deemed moderate. It's also significant to understand that world-wide average radiation exposure from natural sources is approximately 3 millisieverts (mSv), or 300 millirem (mrem), indicating that high-level exposure far exceeds normal background radiation levels. Shielding, maintaining distance, and minimizing exposure time are critical strategies in radiation protection.