Geoscience Reference
In-Depth Information
rays and invented the first X-ray machine. Roentgens were primarily used to measure the
strength of X-rays and gamma rays. Since different types of radiation do not have the same ef-
fect on the human body, the “rem” was developed to more accurately describe a radiation-
dosage level as it pertains to its effect on the human body, and the sievert is a similar “dose-
equivalent” measurement of radiation. One mSv is equal to 0.1 rem. A rem is essentially a
roentgen multiplied by a factor that takes into account the specific type of radiation's effect on
a human body, and for our purposes assume that Rs, rems, and rads are essentially interchange-
able.
The lethal dose of radiation varies considerably from person to person, but it is generally
accepted that about 50 percent of the people exposed to a dose of roughly 4,500 mSv (450
rems) will eventually die from radiation poisoning. By comparison, the average background ra-
diation rate for a person living in America (varies by location) is approximately 3 mSv per
year, the standard limit of exposure to radioactivity for nuclear workers in the United States is
20 mSv per year, and the criteria imposed for relocation after Chernobyl was a lifetime expos-
ure of 350 mSv. It is now common in some parts of Iran, India, and Eastern Europe for back-
ground radiation levels to exceed 50 mSv per year.
Table 17-1. Short-Term Health Effects of Radiation
Exposure
(mSv)
Health Effect
0-250
• May be changes in blood chemistry, but no long-term effects
• May cause nausea and vomiting for 1-2 days
• May cause hair loss in 2-3 weeks
• Disabling sickness not common
250-1,000
• Nausea and fatigue
• Vomiting if dose is 1,250 mSv or more
• May cause hair loss in 2-3 weeks
• Longer term reduction in some types of blood cells
• Most people will recover without medical treatment
1,000-,000
• Nausea and vomiting on first day of exposure
• Hair loss in 2-3 weeks
• Up to a two week latent period followed by appetite loss, general malaise, sore throat, pallor,
diarrhea, and moderate emaciation
• Most people will recover unless they succumb to ancillary infection
2,000-3,000
• Nausea, vomiting, and diarrhea in first few hours
• Up to a one week latent period followed by appetite loss, fever, and general malaise in the second
week
• Followed by bleeding, inflammation of mouth and throat, diarrhea, and emaciation
• Some deaths in 2-6 weeks, followed by eventual deaths of 50% at exposure of 4,500 mSv (worse
as exposure increases)
3,000-6,000
• Nausea, vomiting, and diarrhea in the first few hours
• Rapid emaciation and death in the second week
6,000-10,000
