UNITED NATIONSREPORT OF THE
UNITED NATIONSSCIENTIFIC COI\IMITTEE
ON THE
EFFECTS OF ATOMIC RADIATIONNOTEThroughout this report and its annexes cross-references are denoted by a letter
followed by a number: the Jetter refers to the relevant technical annex (see Tableof Contents) and the number is that of the relevant paragraph. \Vithin each technicalannex, references are made to its individual scientific bibliography by a number
without any preceding letter.
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.

ANNEXES

Annex A

DEFINITIONS O F QU-mITIES, UNITS AND SYMBOLS
1. The 1956 report of the International Colnmission
on Radiological Units and n/leasurementsl gives thefollowing definitions of quantities and units used inradiological physics.*"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 - ~ h eunit of integral absorbed dose is the granrrod. 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 garttnta radiation ata certain place is a measure of the radiation that isbased upon its ability to produce ionization.
"1.8 The unit of exposure dose of X- or gamma
radiation is the roetttgen ( 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 Exposure dose rate is the exposure dose perunit time.
"1.10 The unit of exposure dose rate is the roenfgett
per unit titne.
"1.11 Intetlsity of radiation (radiant energy flax
density) at a given place is the energy per unit timeentering a small sphere of unit cross-sectional areacentred at that place.
"1.12 The unit of intensity of radiation may be erg
per square centimeter second, or watt per square centimeter.

"1.13 The unit of quantity of radioactive material,evaluated according to its radioactivity, is the czrrie(c). One curie is a quantity of a radioactive nuclide
in which the number of disintegrations per second is
3.700 x 1O1O.
"1.14 Specific gatiznta-ray emission (specific gamma-ray output) of a radioactive nuclide is the esposure dose rate produced by the unfiltered gamma
rays from a point source of a defined quanttty of that
nuclide at a defined distance.
"1.15 The unit of specific gamma-ray emission isthe roentgen per ttzilluurie hour (r/mch) at 1 cm.
"1.16 Linear elrergy transfer ( L E T ) is the linear
rate 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 murort ( k e ~ / ~ ) .
"1.18 Mass stopping power is the loss of energy
per unit mass per unit area by an ionizing particle
traversing a material medium.
"1.19 Mass stopping power may be conveniently expressed in kilo electro~zvolts per ,dlligram per squareceltti~neter(kev cm2/mg) ."2. The RBE symbol is described in the I.C.R.U. report, in the follo\ving way:
"2.1 RBE (relative biological effectiveness) isused to compare the effectiveness of absorbed doseof radiation delivered in different ways. I t has beencommonly represented by the symbol 7. It signifies
that m rads delivered by a particular irradiation procedure produces a biological response identical withthat produced by rn? rads delivered by a differentprocedure.
The statement that 'the RBE of a radiation relative to y radiation is 10' signifies that m rads of aradiation produces a particular biological response in
the same degree as 10m rads of y radiation. This
statement may be further summarized as 7 a = 10.

*Symbols and nomenclature. There are numerous national
and international bodies that have reached varying degrees ofacceptance of the use of symbols and units f o r physical quantities. However, there is no universal acceptance of any one setof recommendations. I t is suggested that each country modify
the symbols used herein, in accordance with its own practices.
Thus one may write: kev, keV, or Kev; "C or C"; rad perunit time, rad per time, or rad divided by time: rad/sec, rad/s,
or rad-s-I ; etc. The most generally accepted system of symbols
and units may be that contained in document U I P 6 (1955)
prepared by the International Union of Pure and Applied Phys~cs.These are in fairly close a reement wid1 the recommendations of the International ~tanfardizationOrganization project
ISO/'TC 12, the ConfCrence GCneralc de Poids et Mesures,Union Internationale de Chimie Pure et AppliquCe, and theInternational Elcctrotechnical Committee.
NOTE:Throughout this report and its annexes cross-refercenes are denoted by a letter followed by a number : the letterrefers to the relevant technical annex (see Table of Contents)
and the number is that of the relevant paragraph. Within eachtechnical annex, references are made to its individual scientificbibliography by a number without any preceding letter.

The concept of RBE has a limited usefulness because the biological effectiveness of any radiation depends on many factors. Thus the RBE of two
radiations cannot in general be expressed by a single
factor but varies with many subsidiary factors, suchas the type and degree of biological damage (and hencewith the absorbed dose), the absorbed dose rate, thefractionation, the oxygen tension, the pHt and thetemperature.
"2.2 RBE dose is equal numerically to the productof the dose in rads and an agreed conventional valueof the RBE with respect to a particular form of radlation effect. The standard of cornpailson is X- or
gamma radiation having a LET in water of 3 kev/cc
delivered at a rate of about 10 rad/min.
same"2.3 The unit of RBE is the refit. It has
inherent looseness as the RBE and in adbtlon assumes conventional and not necessarily measuredYvalues of RBE. I t is therefore recommended that its
use be restricted to statements relating to radiation
protection. For esample the statement might be made:The permissible weekly whole body RBE dose is
0.3 rem regardless of the type of radiation to which aperson is exposed.
Should occasion arise when results have been evaluated with other than agreed conventional values ofRBE, the values used should be clearly stated.
I n the case of mixed radiations the RBE dose isassumed to be equal to the sum of the products of theabsorbed dose of each radiation and its RBE :RBE dose in rerns = L [(absorbed dose in rads) x
RBE] ."REFEREXCE
1. International Commission on Radiological Unitsand Measurements (ICRU) : Report oi the ICRU,
1956. U.S. National Bureau of Standards, Handbook 62,
IVashington 1957.

Appendix

LIST O F SCIENTIFIC EXPERTS
The scientific experts who have taken part in the preparation of the report while attending Committee sessions
as members of national delegations are listed below. The Committee must also express its appreciation to the many
individual scientists not directly connected with national delegations whose voluntary co-operation and good willcontributed in no small measure to the preparation of the report.
ARGENTINA:
Dr. C. Nuiiez (Representative)
Dr. D. J . Beninson
Professor E. Favret
Dr. N. Nussis
Dr. J. A. Olarte
AUSTRALIA:
Dr. C. F. Eddy (Representative-first
Mr. D. J . Stevens (Representative)
Dr. A. R W. Wilson

Dr. A. Halawani (Representative)
Dr. H. T. Dawsession)

BELGIUM:
Professor Z. Bacq (Representative)
Mr. R. Boulenger
Dr. M. Errera
Professor F. Twisselman
BRAZIL:
Professor C. Chagas (Repesetrtative)
Dr. B. Gross
Professor N. Libanio
Professor C. Pavan
Father F. X. Roser, S.J.
CANADA:
Dr. E. A, Watkinson (Representative)
Dr. R. K . Appleyard
Dr. P. M. Bird
Dr. W. E. Gnunmitt
Dr. Colin Hunter
Dr. G. H. Josie
Dr. C. A. Mawson
Dr. H. B. Newcombe
Dr. F. D. Sowby
CZECHOSLOVAKIA:Professor F. Hertik (Representative)
Professor F. BEhounek
Dr. M. HaSek
Dr. L. Novik
Professor V. Sobek
Dr. I. Ulehla
Dr. V. Zelenf

Professor L. Bugnard (Representative)
Dr. A. Allisy
Dr. J. Coursaget
Dr. H. Jammet
Dr. J. Labeyrie
Dr. J. Lejeune

INDIA:
Dr. V. R. Khanolkar (Representative)
Dr. A. R. Gopal-Ayengar
Dr. A. S. Rao
JAPAN :

Dr. M. Tsuzuki (Representative)
Dr. Y. Hiyama
Dr. D. Moriwaki
Dr. K. Murati
Dr. M. Nakaidzumi
Mr. S. Ohta
Dr. N. Saito
Dr. E. Tajima
MEXICO:
Dr. M. Martinez Baez (Representative)
Dr. F. A. Andrade
Dr. H. Zalce

Professor R. M. Sievert (Representative)
Dr. B. A. A. Aler
Dr. R. G. Bjarnerstedt
Professor G. Bonnier
Professor T. 0. Caspersson
Professor C. A. T. Gustafsson
Dr. A. G. A. Nelson* Now in the United Arab Republic.

UNIONOF SOVIETSOCIALISTREPUBLICS:
Professor A. V. Lebedinsky (Representative)
Professor K. K. Aglintsev
Professor B. M. Isaev
Professor P. M. KireevProfessor A. N. KraevsLy
Professor A. bZ. Kuzin

UNITEDKXNGDOM
OF GREATBRITAINAND
NORTHERNIRELAND
Professor W. V. Mayneord (Represetltativefirst session)
Dr. E. E. Pochin (Represelztative)
Dr. T. C . Carter
Mr. A. C. Chamberlain
Dr. W. G. Marley
Mr. N. G. Stewart

Dr. Shields Warren (Represe~rtative)
Professor G. W. Beadle
Dr. A. M. Brues
Professor J. Crow
Professor Th. Dobzhansky
Dr. C. L. Dunham
Mr. Merril Eisenbud
Professor Sterling Emerson
Professor G. Failla
Dr. J. H. Harley
Dr. J. S. Laughlin
Professor J. V. Nee1
Dr. M. Zelle