What amount of radiation can kill you?
The Sunday Nation
Nairobi,
24 August 2014
Last week’s article carried the following statements: “…the Apollo spacecrafts passed through the low density zones and also at very high speeds so the crafts spent less than 10 minutes inside. It is estimated that the outer surface of the space crafts received only about 10% of the radiation”
Curiously, no moon hoax proponent has come out to challenge me about that. I say so because the above statements are incorrect! If you were exposed to 10 per cent of the radiation in the van Allen Belts, you would surely die!
What I had actually written is this: “It is estimated that the outer surface of the space crafts received only about 10% of the radiation that can cause sickness”. But the editors deleted the last four words, perhaps in a bid to save space. Their seemingly simple action changed the meaning completely!
Now in the International System of Units (SI), the amount of radiation absorbed by a body is measured in “gray” (symbol = Gy). One gray (1Gy) is equal to one joule of radiation energy per kilogram of matter. There are other units used in medicine designed to make things easier for doctors but all of them are derived from the gray.
Exposure to one gray of radiation in less than one day can cause minor radiation sickness – so called Acute Radiation Syndrome (ARS). Usually, this is not fatal but victims may experience nausea and vomiting. 2Gy to 10Gy will have serious health effects and anything above 10Gy will definitely kill!
When you go for an x-ray picture, you get exposed to only a few hundredths of gray of radiation; that is below 0.01Gy. This dose is quite safe for patients but the operators of the x-ray machine must take extra caution – after all, they spend half their working life in that room!
So now you understand why the radiologist wears a heavy protective overall and walks out of the x-ray room before switching on the machine – the radiation is not dangerous to the patient but it can harm the operator due to prolonged exposure.
Now going back to the Apollo Missions, the spacecrafts spent less than 10 minutes in the low intensity regions of the van Allen Radiation Belts. Cumulatively in the round trip, the outer surface of the craft received about 1Gy.
If the Astronauts were outside the spacecraft (and naked!) they would have experienced minor radiation sickness. But they were inside a radiation shielded capsule that allowed only about 0.01Gy in the ten minutes of flight through the van Allen Belts; that is, about the same as what you get when you go for an x-ray picture.
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