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Institute of Medicine (US) Committee on Thyroid Screening Related to I-131 Exposure; National Research Council (US) Committee on Exposure of the American People to I-131 from the Nevada Atomic Bomb Tests. Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications. Washington (DC): National Academies Press (US); 1999.

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Exposure of the American People to Iodine-131 from Nevada Nuclear-Bomb Tests: Review of the National Cancer Institute Report and Public Health Implications.

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See Atomic Bomb Casualty Commission.

Atomic Bomb Casualty Commission (abbreviated ABCC)

The agency of the Japanese Ministry of Health and Welfare and the U.S. National Academy of Sciences charged with the responsibility for the study of the survivors of the atomic bombings from the inception of the investigations in 1947 until 1975.

Becquerel (abbreviated Bq)

The measure of activity proposed by the Systeme International and equal to one nuclear disintegration per second.


See Becquerel.


See Curie.

Curie (abbreviated Ci)

The measure of activity used until the introduction of the Becquerel. One Curie is equal to 3.7 × 1010 nuclear disintegrations per second or to 3.7 × 1010 Becquerels.


See dose and dose-rate effectiveness factor.

Dose and dose-rate effectiveness factor (abbreviated DDREF)

A measure of the extent to which radiation-related damage accruing at a high dose rate is ameliorated when the dose rate is low. This value will presumably vary with the endpoint measured, but it is not known precisely for such endpoints as incidence of or death due to cancer. Experimental studies suggest a value between 5 and 20, but the epidemiological data derived from the studies of the atomic bomb surveyors imply a lower number, possibly 1 to 2.


See excess risk.


See excess risk.

Excess risk

Risk, whether it is relative or absolute, is often expressed in terms of the excess that it represents over expectations in the absence of exposure to a carcinogenic agent, radiation in this instance. Excess relative risk (ERR) is, therefore, merely the observed relative risk minus 1, the value expected in the absence of an effect of radiation. Similarly excess absolute risk (EAR) is the number of incident cases or deaths at a particular dose above the number that would be expected in the absence of a radiation-related increase.


Technically, exposure is the amount of air ionized by radiant energy, specifically, the amount of electrical charge produced in 1 cc of air under condition of electron equilibrium. More commonly, and in the present context, it simply means the presence of an individual in a field of radiation.

Geometric mean (abbreviated GM)

The geometric average of a series of n positive numbers; it is equal to the nth root of their product. As an illustration, the geometric mean of the numbers 2 and 8 is the square root of 16 (their product) or 4. The GM is approximately the median (50th percentile) of a distribution of numbers whose logarithms are normally distributed.

Geometric standard deviation (abbreviated GSD)

The geometric standard deviation is the antilog of the standard deviation of the natural logarithms of a set of numbers. The GSD is usually used to describe the variation of a set of data that is positively skewed.


See geometric mean.

Gray (abbreviated Gy)

The SI unit of absorbed dose equal to 1 joule per kilogram, or 100 rad. The unit derives its name from the English biophysicist Louis Harold Gray.


See geometric standard deviation.


See Gray.


Kriging is defined as the process of estimating the value of a spatially distributed variable from adjacent values while considering their interdependence.

Probability of causation

A number that expresses the probability that a given cancer, in a specific tissue has been caused by a previous exposure to a carcinogenic agent, such as ionizing radiation.


The unit of absorbed dose used prior to the introduction of the Gray. One rad is equal to 100 ergs per gram or 0.01 Gy.

Radiation Effects Research Foundation

The research institution currently charged with the study of the health effects of exposure to the atomic bombing of Hiroshima and Nagasaki; it is the successor to the Atomic Bomb Casualty Commission and is jointly administered and funded by the governments of Japan and the United States.


The washing out of radionuclide-containing particles by rain falling to the earth's surface.


See relative biological effectiveness.

Relative biological effectiveness (abbreviated RBE)

The biological effectiveness of one form of radiation as compared with another to produce the same biological endpoint. It affords the means to combine doses when an individual is exposed to a variety of forms of radiation.


The “dose equivalent” (H) and its unit, the rem (roentgen equivalent-man), were introduced to account for the different biologic effects of the same absorbed dose from different types of radiation; H is the product of D, Q, and N at a point of interest in tissue, where D is absorbed dose, Q is the quality factor, and N is the product of any other modifying factors (1 rem = 0.01 Sv).

Risk, absolute (abbreviated AR)

The excess number of deaths (or cases) above that “normally” expected in some population in the absence of exposure to ionizing radiation beyond that to which everyone is subjected because of the radiation emanating from the earth's crust or originating in outer space.

Risk, attributable

The percentage of deaths or cases ostensibly assignable to a specific cause, in this instance, ionizing radiation.

Risk, relative (abbreviated RR)

The ratio of the risk in one population to that in another; for example, the ratio of the risk among individuals exposed to 2 Gy as contrasted with the background risk.


The Surveillance, Epidemiology, and End Results (SEER) Program was developed as a result of the National Cancer Act of 1971, which mandated the collection, analysis, and dissemination of all data useful in the prevention, diagnosis, and treatment of cancer. SEER is a continuing project of the National Cancer Institute to collect cancer data on a routine basis from designated population-based cancer registries in various areas of the country.

Sensitivity analysis

An analysis of the variation in the solution of a problem with variation in the values of the parameters involved. Basically, it is a method of determining how dependent a solution may be on the values assigned to the parameters in a model by the investigator(s).

Sievert (abbreviated SV)

A unit of dose equivalent to the dose in Gray times a quality factor times any other factors that may modify the dose. The name is derived from the Swedish physicist Rolf M. Sievert.


Standardized incidence rate is the incidence (new cases in a time interval) rate adjusted to a population of standardized age distribution. It is usually equal to the ratio of the number of observed cases to the number of expected cases.


Standardized mortality rate is the mortality (death) rate adjusted to a population of a standardized age distribution. It is usually equal to the ratio of the number of observed deaths to the number of expected deaths.


See Sievert.

Uncertainty analysis

Models are merely approximations of real systems, and as such their predictions are inherently uncertain. Uncertainty analysis seeks to quantify the error inherent in each step in the modeling process and to propagate these errors through the entire process in order to estimate the overall possible error (or uncertainty).

Copyright © 1999, National Academy of Sciences.
Bookshelf ID: NBK100849
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