REPORT OF THE

UNITED-NAXI-ONS .

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EFFECTS OF !iit}ifffHiADIATION.. : . . .

·'GENERAL ASSEMBLY
OFFICIAL RECORDS : SEVENTEENTH SESSIONSUPPLEMENT No. 16 {A/5216}

New York, 1962

NOTE
Throughout the present report and the annexes thereto, references to theannexes are indicated by a letter followed by a number: the letter denotes the relevant
annex and the number the paragraph therein. Within each annex, references to its
scientific bibliography are indicated by numbers.
Symbols of United Nations documents are composed of capital letters combined with figures. Mention of such a symbol indicates a reference to a United
Nations document.

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ANNEX A

DEFINITIONS OF QUA.l'n'ITIES, U1'1TS AND S1"lIBOLS
1. The Committee has used in the present report theradiological quantities and units defined in the 1959
report of the International Commission on RadiologicalUnits and Measurements (ICRU), 1 the relevant part ofwhich is reproduced below.* It should however be notedthat ICRU has appointed an ad hoe committee to examine
the quantities and definitions of units and some modifications of existing definitions may shortly be recommended.
"1.1. Absorbed dose of any ionizing radiation is theenergy imparted to matter by ionizing particles perunit mass of irradiated material at the place of interest.
"1.2 The unit of absorbed dose is the rad. One radis 100 ergs/g.
"1.3. Integral absorbed dose in a certain region isthe energy imparted to matter by ionizing particles inthat region.
"1.4. The unit of integral absorbed dose is the gramrad. One gram rad is 100 ergs.
"1.5. Absorbed dose rate is the absorbed dose perunit time.
"1.6. The unit of absorbed dose rate is the rad perunit time.
"1.7. Exposure dose of X- or gamma radiation at acertain place is a measure of the radiation that is based
upon its ability to produce ionization.
"1.8. The unit of exposure dose of X- or gamma
radiation is the roentgen (r). One roentgen is an exposure dose of X- or gamma radiation such that theassociated corpuscular emission per 0.001293 g of air
produces, in air, ions carrying 1 electrostatic unit ofquantity of electricity of either sign.
"1.9. Ex-pos1ire dose rate is the exposure dose perunit time.
"1.10. The unit of exposure dose rate is theroentgen per unit time.
"1.11. Intensity of radiatioti (radiant energy fluxdensity) at a given place is the energy per unit timeentering a small sphere centered at that place per unit
cross-sectional area of the sphere.

"l.12. The unit of intensity of radiation may be
erg per sqitare centimeter second, or watt per squarecentimeter.
"1.13. The unit of quantity of radio-active material,evaluated according to its radio-activity, is the curie( c). One curie is a quantity of radio-active nuclide
in which the number of disintegrations per second
is 3.700 X 10 10•"1.14. Specific gamma-ray emission (specificgamma-ray output) of a radio-active nuclide is theexposure dose rate produced by the unfiltered gamma
rays from a point source of a defined quantity of that
nuclide at a defined distance.
"1.15 The unit of specific gamma-ray emission isthe roentgen per millicurie hoitr (r/mch) at 1 cm.
"1.16. Linear energy transfer (LET) is the linearrate of loss of energy (locally absorbed) by an ionizing particle traversing a material medium.
"1.17. Linear energy transfer may be conveniently
expressed in kilo electron volts per micron (kev/14).
"1.18. Mass stopping power is the loss of energy
per unit mass per unit area by an ionizing particle
traversing a material medium.
''l.19. Mass stopping power may be conveniently
expressed in kilo electron volts per milligram persquare centimeter {kev cm 2/mg)."
2. According to ICRU :1"The absorbed dose, D (in rads), of any radiationmust be multiplied by an agreed £'actor, RBE (~elative
biological effectiveness), whose values for different
radiations are laid down by the International Commission on Radiological Protection (ICRP). This
product, called the RBE dose, is e.xpressed in rems
whereRBE dose (in rems) = (RBE) (D)"In the case of mixed radiations the total RBE
dose is assumed to be equal to the sum of the productsof the absorbed dose of each radiation and its RBE.

*The following is quoted from the above-mentioned ICRU •report:"Symbols and P10111enclature. There are numerous nationaland international bodies that have reached varying degrees ofacceptance of the use of symbols and units for physical quantities. However, there is no universal acceptance of a11y one setof recommendations. It is suggested that each country modify
the symbols used herein, in accordance with its own practices.
Thus one may write: kev, keV, or Kev; HC or CH; rad per unit
time, rad per time, or rad divided by time; rad/sec, rad/s, orrad.s-1 ; etc. The most generally accepted system of symbols andunits may be that contained in document UIP 6 (1956) preparedby the International Union of Pure and Applied Physics. These
are in fairly dose agreement with the recommendations of theInternational Standardization Organization project ISO/TC 12,
the Conference Generale de Poids et Mesures, Union Intema·tionale de Chimie Pure et Appliquee, and the International
Electrotechnical Committee."

39"RBE dose (in rems)rads) (RBE) ]."~ [ (absorbeddose inFor the sake of simplicity in the present report 1roentgen of X-, beta or gamma radiation is assumed tocorrespond to a tissue dose of 1 rad and, since the RBEof these radiations is conventionally unity, the tissue
dose may also be expressed as 1 rem.
3. The RBE values that have been used in the present
report are those established by ICRP in establishingprotection standards. The table below gives the valuesof RBE for different types of radiation. 2 The ICRP
Committee on REE is currently examining the conceptand use of RBE in radiation protection calculations andnew recommendations may shortly be made.

TABLE I. RBE v.um:s

1. X-rays, elcctrOt1s and positrons of any specific io11i.1:atio11

RBE=l
2. H tavy ioni.r:ing particles
Arerage spaifie ionization(ion pairs Permicro.s of wakr)

100 or less .•••.•..•.•.•.•....•.......•.• • .••••..••
100 to 200 ...••.•..•. ,, . • .....•..•...........•....
200 to 650 .••.....•...•....•.........•..•••••....•
650 to 1,500, • •.•...••...•..•...•..•. , . . .. . .. • ••. • .
1,500 to 5,000 ..••..•.•.••........... • •.•... . .....•.•RBE

Aoerage litUar <>•errylranJf#T to water(kn ta micr°")

11 to 2
2 to 55 to 1010 to 20

3.5 or less
3.5 to 7.0
i.O to 23
23 to 53
53 to 175

For practical purposes, an RBE of 10 is applicable to fast neutrons and protons up to 10
MeV and an RBE of 20 to heavy recoil nuclei for whole-body irradiation and the most sensitive
critical organs.

REFERENCES
1. Report of the International Commission on Radiological Units and Measurements(ICRU) (1959). National Bureau of Standards, Handbook 78.
2. Recommendations of the International Commission on Radiological Protection.
Brit. J. Radial. Suppl. No. 6 (1955).

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