Acute Effects of Exposure to Ionizing Radiation
Dose (rem)
Effect
25-50
Blood changes. For example, white blood cells
begin to disappear. Temporary sterility in men.
75
Vomiting in 10 percent of those exposed.
200
Depression or ablation of bone marrow. Nausea
and vomiting within hours. Epilation (loss of
hair) within 2 or 3 weeks.
300
Erythema (reddening of the skin).
450
Lethal dose for 50 percent of those exposed.
Death within 30 days.
1000
Loss of intestinal wall.
weeks.
2000
Unconscious within minutes, death within a few
Death within 1 or 2
hours.
¢
Examples of delayed effects include cataracts, several forms of cancer,
and genetic disorders in offspring.
Cataracts appear after a latency period
of several years and require a threshold dose of at least 200 rem.
Genetic
effects have been demonstrated only in animal studies; they have not been
observed in humans.
For example, data collected on more than 30,000 offspring
of people irradiated at Hiroshima and Nagasaki did not reveal statistically
significant increases in stillbirths, neonatal deaths, birth weight, or
congenital malformations (2; 3).
According to current medical knowledge, no threshold dose is required for
cancer induction.
Since cancer occurs naturally in the general population and
cannot be distinguished from radiation-induced disease, the problem of risk
assessment, especially at low doses, is complex.
The only way to determine
the magnitude of the cancer risk is to study large groups of exposed personnel
and compare their cancer incidence with that of a similar, unexposed group.
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