How much radiation is deadly?

Answer 1

Lethal radiation dose varies, depending on physical condition and care given after receipt of dose. There is a grey area (no pun intended) between 6 and 8 Grays (a unit of ionizing radiation), equivalent to about 600 to 800 rads (in the old nomenclature), where 95% to 100% of those untreated will die, and 50% to 100% of those treated will die. Above 8 Grays, 800 rads, 100% will die.

For gamma radiation, one Gray is approximately equal to one Sievert, which is a unit of dose equivalent for biological tissue, so these numbers are comparable, i.e. 8 Sieverts or 800 rem.

Answer 2

Approximately 500,000 to 1,000,000 millirems full-body exposure would usually cause a fatal dose to be delivered to the bone marrow, with death in about 10-20 days as the destroyed red and white blood cells were not replaced. By comparison, a full body CT scan would cause an exposure of about 5,000 millirems, with a CT scan for specific organs and chest X-rays being only a fraction of this.

Answer 3

All radiation is potentially dangerous. Visible light is radiation and can damage your eyes if the intensity is high enough. However, ionizing radiation is the radiation that people would consider dangerous. This type of radiation is above the visible light spectrum. Ionizing radiation has a high energy that can damage DNA causing mutations or cell death. Ionizing radiation includes UV radiation, x-rays and gamma-rays. Radiation below the visible light spectrum can also be considered dangerous as it can produce thermal currents which can cause death in extreme cases. Examples would be microwaves and radio waves.