2019  
KENYA STANDARD  KS 2030:  2019  
ICS 13.280   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Discharge of patients undergoing 
treatment with radioactive substances — 
Code of practice  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
© KEBS 2019                                                                                                        Second Edition 2019  
  
TECHNICAL COMMITTEE R EPRESENTATION  
 
The follow ing organ izations were represented on the  Technical C ommittee:  
 
Eastern Africa A ssociation f or Radiation Prote ction (EAARP)  
Kenya Airways - Non Destructive Testing Department  
Kenya Industrial Research and Development Institute - Energy Division  
Kenya National Accreditation Service  
Kenyatta National Hospital -Radiation Safety Department  
Kenya Nuclear Electricity Board  
Kenyatta University - Department of Applied Physics  
Ministry of R oads and Publ ic Works — Materials Testing and  Research D epartment  
National Commission for Science, Techn ology and Innovation  
Non Destructive Testing Society of Kenya  
Radiation Pr otection Bo ard 
SGS limited Kenya  
Kenya Bure au of Standar ds — Secret ariat 
 
 
 
 
 
REVISION OF KEN YA STANDARDS  
 
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for improv ements to publ ished st andards, address ed to the Mana ging Direct or, Kenya Bure au of Standar ds, 
are welcome.  
 
 
 
 
 
 
© Kenya  Bureau  of Standards,  2019 
 
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in all Kenya Standards  and except  as provided under  Section 26  of this Act, no Kenya Sta ndard produced  by Kenya Bureau of Standards  
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ISBN 9966 -19-766-4 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Discharge of patients undergoing 
treatment with radioactive substances — 
Code of practice  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
KENY A BUREA U OF STANDARD S (KEBS)  
 
Head  Office:  P.O. Box 54974,  Nairobi -00200,  Tel.: (+254  020) 605490,  602350,  Fax: (+254 020) 604031  
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 Foreword 
 
This Kenya Standard w as prepared by the  Technical Commi ttee on Dos imetry  Radiotracer and N on 
Destructive Testing  and it is in accordance with the procedures of the Bureau.  
 
The purpose of this standard is to provide guidance on the requirements  and conditio ns that should be met 
for the discharge from a hospital  or clinic of a patient who is undergoi ng treatment  with a radio active su bstance, 
and the co nditions for the treatment of an outpatient. In the conte xt of these recomme ndatio ns, disch arge of  
the patient  means the ret urn of the pati ent into the c ommunity,  and appli es equally to the patient who  has been 
admitted  to a hospital  for the treatm ent and to the patient  who has  been administ ered the treatment as an 
outpati ent. 
 
These r ecommendati ons are based on the pr emise t hat the radiati on dose to perso ns with w hom the patie nt 
may make  contact  outsi de the hospital  or clinic should be kept as low  as reasonably  achievable,  taking  into 
acco unt the particul ar social  and economic factors,  and does not exce ed the relevant  dose limit prescribed 
by regulati on. 
 
During the preparation of this st andard, the followi ng publ ications were ref erred to: 
 
ICRP, 1996. Radiological Protection and Safety in Medicine. ICRP P ublication  73. Ann. ICRP 26 (2)  
 
ICRP, 1988. Radiation Dose to Patients from Radiopharmaceuticals. ICRP Pub lication 53. Ann. ICRP 
18 (1 -4) 
 
Natio nal Council on Radia tion Protection and Measurements, Dose  limits  for individua ls who receive 
exposure fr om radi onuclide therapy pat ients, NCRP.  
 
The R adiation Protecti on Act, CAP 24 3, of the Laws of Kenya, 1985 (revis ed) 
 
Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards, General 
Safety Requirements Part 3  
 
 
 
The ass istance derived fr om these  sources is h ereby ackn owledged. 
 KENYA  STANDARD                                                                KS 2030:  2019  
 
Discharge  of patients  undergoing t reatment  with radioactive  substances  
— Code  of practice  
 
1        Scope  
 
This stand ard relates  to the treatment  of patients with  sealed or unsealed  forms  of a radio active substance. It 
takes into account the do se rate external  to the patient, the potential for loss of a sealed source  from the 
patient,  and the potential for the spread of contamina tion of an unseal ed radio active substance that is excret ed 
by the patient.   
 
The requirements for the disch arge of  individual  patien ts should be  assessed by a medical sp ecialist who hol ds 
an ap propriate license, prefer ably in co nsultation with an experie nced me dical phys icist, having reg ard to the 
prevail ing circ umstances.  
 
 
 
2        Radiation  protection  criteria for patient discharge  
 
2.1      Dose  limits  and dose  constraints  
 
The effective  dose  to any member  of the general public shou ld not exce ed 1 millisievert  (mSv)  in a year, 
exclud ing exposure fr om natural backgro und radiation and med ical proced ures. This dose limit applies to adults 
and c hildren,  including the unborn child. In the context  of these re quirements,  the dose limit appli es to perso ns 
who may  make cont act with the  patient, for example, throu gh work, travel,  social or domestic activitie s. 
 
Adult  family  memb ers or perso ns who care  for the patient  are not necessarily subject to the 1 mSv dose  limit 
for members of the public. The effective dose  to an appropriately  inform ed carer who knowingly and willingly 
provid es comfort and support to the patient should not exceed a  dose  constraint of 5 mSv per treatment 
episode.  This criterion need not be appl ied rigidly in all cases, as for example w hen a parent is assisting wi th 
the care of a sick child.  
 
2.2      The discharge  of patients  following treatment  
 
Patients  may be  discharged from hospital  or may lea ve a clinic following treatm ent with a radioactive substance 
when an  estimate of the ef fective  dose to family  members and to memb ers of the general public has been 
shown to c omply with the d ose limits and d ose co nstraints given in 2. 1. 
 
Such  an estimate  should be based  on measuremen ts of the external  ambi ent dose  equivalent rate from the 
patient,  the physical  half-life of the radionuclide, the biolog ical clearance of the radioactive subst ance from 
the body, the patient 's clinical condition  and the proximity to other  family  mem bers, especially children, and 
to other  persons.  The dose estimat es, and the measurem ents on which  they are based, should be recorded 
in the patient 's clin ical rec ord. 
 
2.3      Maximum  external  dose  rate from  an inpatient  at the time of discharge  from  hospital  
 
When patient-specific dose estimates to family members and to  members of  the general public are not 
available,  it is recomm ended that, in order to comply with the criteria given in 2.1, the ambient  dose 
equivalent  rate at a distance of 1 m from a  patient who is undergoing treatment  with a radioactive substance 
should not exce ed 40 µSv/h  at the time of the patient's discharge from hospital.  Measuremen ts at distances 
of 2 m or 3 m may be more appropr iate in the clinical setting, th us limiting  the radiation  exposure to the staff 
and minim ising any effects  arising from the no n-uniform activity distribution in the  patient.  
 
The patient does not r epresent a poin t-source of activity, so that  the inverse -square law often  does not apply 
until at least 3 m from the patient.  The exter nal ambient  dose equivalent  rate from iodine-131 distributed 
within  a pati ent may be approximat ed by an ‘inverse 1.5  power’ relationship  from 1 m to 3 m.   
 The total external r adiation dose  to members of the public and  to family memb ers will  depend not  only on  the 
dose  rate at the time of discharge  but also on the phys ical decay rate of the radionuclide, the biolog ical 
clearance rate of the rad ioactive  substance from the pat ient, and the time sp ent by the patient in proximity to 
these persons. The abo ve-recomm ended level of 40 µSv/h at 1 m has prim arily be en derived from 
considerations of iodi ne-131 in the tr eatment of thyro id disorders. It shou ld be equally applicable to other 
thera peutic  uses of iodin e-131, and to other  therapeutic radionuclides,  even  though  the ra tes of phys ical decay  
and biological clearance  may differ. However, the rates of  physical  decay and  biological clearance will 
determ ine the  period  during which radiation  safety restrictions  will apply, particularly  in relation  to the 
exposure  of family  memb ers, and the time at which the patient  may resume  normal  employment  and s ocial 
activities ( see Clau se 3, Instru ctions for patient s). 
 
Where the patient’s circ umsta nces are such that the dose limits or dose co nstraints given in 2.1 cou ld be 
exce eded even though the ambient  dose equivalent rate  at 1 m from the patient  is below 25 µSv/h,  the 
respo nsible medical sp ecialist sh ould postpone the disch arge of  the patient  until such time that the limits or 
constraints can be met.  
 
2.4      Treatment  of patients  with sealed  sources  
 
The medical specialist with the appropriate license who is responsible for the treatm ent of patien ts with 
sealed so urces of ca esium-137 or iridium-192 must ensure  the safe keeping of  these s ources at all times. 
Consequentl y, a patient  who is undergoing treatm ent with a  sealed so urce or so urces is not to be discharged 
from a h ospital or clin ic until these sourc es have been removed fr om the patient 's body.  
 
Where one or more sea led so urces of  other  radionuclides rema in in a patient  who is to be discharged from a 
hospital  or clinic, consideration  should be  given  to the possibility that these s ources  may be dislo dged from the 
patient, and to the ne ed for ap propriate action to  be taken by the patient or  carer in th is conting ency. 
 
2.5      Treatment  of patients  with unsea led sources  
 
When a patient is to be discharged from a hospital  or a clinic following treatment  with an unsealed source of 
a radionucl ide, cons ideration should be  given  to the possibility  of contam ination  arising from the escape  of 
body  fluids, for example as  a result of urinary incontine nce or  vomiting.  After  oral administrati on of an unseal ed 
radionuclide (e.g. iodin e-131 for thyroid  therapy),  the patient should r emain  at the hospital or clin ic until s uch 
time as the pati ent is unlikely to vomit the administ ered dose. 
 
2.6      Maximum  radionuclide  activity  to be  administered  to an outpatient  
 
In general, the patient may be treated as  an outpat ient if the activity of the radionuclide to be admin istered 
does not exceed  the activity given  in Annex  A for sealed sources or Annex B for unsealed sources.  Where 
the  patient’s  circumst ances  are  s uch  that  the  d ose  limits and dose cons traints  given  in  2.1 could  be 
exce eded e ven though t he activity to be admin istered compl ies with that listed in Annex A or Annex B,  then 
the responsible medical specialist should postpone  the disch arge of the patient  until these c onditio ns can be 
met. 
 
The maxim um radionuclide activities  given in Annex A and Annex B are r ecommen dations for radionuclide 
therap ies used clinically at the time of the writing of these R ecommendati ons. It is ackn owledged  that new 
treatment  proc edures  may  be  deve loped  in  the  future  which  could  render  these  limits  unnecessarily 
restrictive.  If it can be shown for a particul ar treatment that the dose limits and do se constraints given  in 2.1 
will not be exceeded, then the re gulatory  authority  may grant permiss ion to discharge pati ents receiving this 
treatment at activities gr eater than th ose given in these requ irements, upon application fr om the res ponsible 
medical s pecialist. 
 
Where the patient is undergoing  a novel treatment  with a radioactive substance not  listed  in these  Annex es, 
guidance  should  be  so ught  from  the  regulatory  authority.  Further  information  on  the  rationa le  for  the 
maximum  activities  at which  patients may be dischar ged from hospital,  or treated  as an outpati ent, is 
provid ed in Annex C.   
 
2.7      Postponement  of the discharge  of a patient  from  hospital  or clinic  
 
A patient sh ould not be d ischarged from  a hospital or clin ic if it seems likely that:   
  
a)         a sea led source may be l ost; 
 
b)         a spread of contaminati on may occur as a result of t he excreti on of an unseal ed source; or 
c)         the patient may vomit shortly after o ral adminis tration  of an unseal ed source. 
2.8      Discharge  of a patient  to premises  other  than  a private  dwelling 
 
If a patient  is to be transferred to an  institution  or place of care other than a private dwelling,  for example to a 
nursing  home, appropriate notification of  the patient's  radioactive status  shou ld be sent to that place  at the time  
of the transfer.  The notificati on should  include  detai ls of the form and activity of the radionuclide, the time  
and date of admin istration  of the radio nuclide to the patient, the  relevant radiati on chara cteristics of the 
radionuclide, and the precautio ns that should  be observed  for a specifi ed time by the persons who will care 
for the patie nt.  The name of  the h ospital or clinic from which  the patient was discharged should a lso be 
provid ed, together  with the name  and teleph one number  of the person who may  be contacted  in order to obtain 
further information on radiati on protection matters or adv ice in the event of a medical emergency. 
 
2.9      Use of public  transport  by the patient 
 
The time of travel by publ ic transport for the pati ent returni ng home should not exce ed one hours when t he 
patient  is disch arged at a maximum  ambient  dose equivalent  rate of 40µSv/hat  1 m or, for a radionuclide 
that emits p enetrating r adiation,  at the maximum  activity given  in Annex  A or Annex  B. If it is kn own that the 
journey wou ld be of lon ger duration and that the patient inten ds to use publ ic transport, then the pati ent sh ould 
rema in either in hospital or in local premises after dischar ge so that the journey may be deferred until the 
external ambient d ose equivalent rate has fall en to an acc eptable level.  
 
Alternatively,  after taking into consideration the possible dose  to a carer or  any other  person accom panying 
the patient, the patient may be advis ed to travel by means oth er than publ ic transport. Th is is of p articular  
import ance where the p ublic transport involves c onfined adj acent seating at  distances of considerably less than 
1 metre.  
 
3        Instructions  for patients  
 
Individualized  instructions relevant  to the patient’s  medical  and s ocial circumstances sh ould be  provi ded to 
each  patient by  the licensed medical specialist respo nsible for the treatment,  in consultation with  an 
experi enced  medical  physicist.  The instructi ons should state  the radio nuclide, the form of the radionuclide 
and the activity administered, sh ould be designed to suit the p atient's own particu lar travel and d omestic 
arran gemen ts and sh ould be  based on the need  to minimize  the radiati on dose to other  persons, taking into 
acco unt the social and economic  costs. 
 
The instructi ons should be given  to the patient  orally and  in writin g. The  instruc tions should include, wh ere 
appro priate,  the need to restrict close proximity  to other  members of the household, especially  children, 
young  persons and pregnant women,  the importance of good perso nal hygiene  in order to prevent  the 
spread  of contamination, and  the date wh en normal s ocial and employment  activities  may be  resumed. T he 
resumpti on of normal  employment  should take into account  the duration  and dista nce of interacti on with 
other  persons in the workplace.  Similarly,  social  activities which involve  close proximity  to other persons for 
extended  periods, s uch as going  to the cinema  or long journeys by publ ic transport, should be distin guished 
from activities such as  shopping, where there are only  brief encoun ters with oth er perso ns. 
 
Instructions should  also be given,  where appropriate, on the precautions to follow  in situations s uch as medical  
emergencies requiring hospitalization . On the day of treatment,  a written record  of the treatm ent sh ould be 
provided  to the referring doctor and, wh ere appropr iate, to the pati ent and/or carers. Th is record should include 
the following information:  
 
a)         the radi onuclide admin istered, the activ ity administ ered and date of  admin istration; 
b) name(s) and contact number(s) of the prescribing doctor  and/or radiation  safety officer  or medical 
phys icist, for  emerge ncies or oth er hospitalization ; and 
 
c)         the durati on of any pertine nt radiation safety restr ictions.  
  
The patient  should  also be provided  with a card containing  the above informat ion. The card should be c arried 
by the patient at all times until the date s pecified. 
  
Annex A  
(normative)  
 
Maximum activities of radionuclides  in sealed forms at which a 
patient  may be discharge d* 
 
RADIONUCLIDE PHYSICAL  HALF-LIFE  ACTIVITY IN MBq  Note 
Caesium-137 
 
Gold -198 
 
Iodine -125 
 
Iridium -192 
 
Palladiu m-103 30.1 years  
 
2.69 days  
 
59.4 days  
 
73.8 days  
 
17.0 days  None 
 
400 
 
2 000 
none  
10 000  1 
 
- 
 
2, 3 
 
1 
 
2, 3 
 
* This Annex  should be used in c onjunction with 2.2 and 2.6.  
 
 
NOTE  1   Sources  are to be removed  before the patient  is discharged  from hospital.  
 
NOTE  2   Because  of the relatively  long physical half-life of this radionucli de the patient  should  be instructed  to limit periods  spent  in 
close  proximi ty to other  persons,  particularly  children  or someone  who is pregna nt, until the adminis tered radionuclide  has decayed to at 
least  one-eighth  of the amount  listed  in this Annex.  There  would normally  be no restrictions  on the time spent  with a person  who is at a 
distance  of 1 metre  or more from the patient.  
 
NOTE  3   No activity  limit is necessa ry for shielded iodine -125 or palladiu m-103 plaques/applicators. 
  
Annex B  
(normative)  
 
Maximum Activities of radionuclides  in unsealed  forms 
which may be administered to Outpatients * 
 
Radionuclide  Physical half -life Activity in MBq Note 
Indium -111 
 
Iodine -131 
 
Phosphorus-32 
 
Rhenium-188 
 
Samarium-153 
 
Strontium -89 
 
Yttrium -90 2.81 days  
 
8.02 days  
 
14.3 days  
 
17.0 ho urs 
 
1.93 days  
 
50.5 days  
 
2.67 days  400 
 
800 
 
1 200  
 
4 000  
 
4 000  
 
300 
 
4 000  1 
 
2 
 
1. 4 
 
1. 4 
 
1. 4 
 
2. 4 
 
2. 4 
 
* This Annex  should be used in c onjunction with 2.2 and 2.6.  
 
The foll owing notes do  not apply to r adionuclides in radiopharmac eutical forms that are  insoluble or are totally retained in 
the bo dy, e.g. labelled microspheres or col loids. 
 
NOTE 1   An incontinent  patient  should  not be discharged  to a private dwelling  or other non-control led prem ises in the first two days 
after administration  of this  radio nuclide  unless monitoring  of the  patient  or of the  excreted  activity  indicates  that an earlier  discharge  date 
is appropriate.  
 
NOTE 2   An incontinent  patient  should  not be discharged  to a private  dwelling  or other  non-controlled  premises  in the first week after 
administration of  this radionuclide  unless  monitoring  of the patient  or of the excreted activity  indicates  that an earlier discharge  date is 
appropriate.  
 
NOTE 3   An incontinent  patient  should  not be discharged  to a private  dwelling  or other  non-controlled  prem ises in the first two weeks 
after administration  of this  radio nuclide  unless monitoring  of the  patient  or of the  excreted  activity  indicates  that an earlier  discharge  date 
is appropriate.  
 
NOTE  4   In the case  of pharmaceutical  forms  of the radionuclide  where there is rapid  renal  excre tion of activit y, the patient  should 
remain  in hospital  or at the clinic  until one, or preferab ly two, urinary voids  have  occurred.  Monitor ing of the patient  or of the excreted 
activity  may indicate  that an earlier  or later discharge  time is appropriate.  The patient should  receive  appropriate  instructions  to minimize 
the spread  of contamination  from excreta  for at least the next 24 h after  discharge  from the hospital  or clinic. 
  
Annex C  
(informati ve) 
 
C.1      Rationale  for the recommended maximum  activities  administered  to outpatients  and 
the maximum  dose  rate for discharge  of inpatients  from  hospital  
 
The purpose of the stand ard is to provi de guida nce on the conditi ons which  should be met for the disch arge 
of a patient  who is undergoing  treatment with  a radioactive substance. The pri ncipal crit erion is that the effective  
dose  to any member  of the general public, includ ing children and the unborn child,  shou ld not exce ed 1 
millisievert  (mSv) in a year, exclud ing exposure from natural  background radiation  and from medical 
procedures to the  recipient.  
 
The 1 mSv dose  limit is chosen  to be consistent with the ICRP  recomm endatio ns, which set a public 
exposure lim it of 1 mSv in a year (public exposure covers  all exposures arising from pr actices; that is, all 
exposur es that are neither occupation al nor medical). This limit does not necessarily  apply to  adult  family 
memb ers or carers  who are appropriately inform ed and knowingly and willing ly provide  comfort  and support 
to the patient.  
 
An effective  dose c onstraint of 5 mSv is recomm ended for adult family memb ers and carers, but  this criterion 
need  not be rigidly  applied in all cases,  as for example when a parent  is assisting  with the care of a sick 
child.  
 
The approach  taken  in these  requirements , in order  to achieve  the above  criteria under  normal  circu mstances 
is that the ambient  dose equival ent rate at a distance  of 1 m from the patient undergoing treatment  with a 
radioactive substance should not exceed 40µSv/h  at the time of disch arge from a hospital or clinic.  It is 
recogn ized that the patient does not represent  a point -source of  activity,  and that as a co nsequence the 
inverse -square  law does not norma lly apply until dista nces of at least  3 m from the patient. It has been shown  
that, in the case of iodine-131 distributed  within a patient,  the ambient  dose equivalent rate  at dista nces 
from 1 to 3 m from the patient  follows  an approximate  ‘inverse  1.5 power’ relatio nship.  
 
The r ecommended maximum ambient dose e quivalent rate of 40 µSv/h at 1  m from the patient at the time of 
disch arge h as been derived primarily from considerations of iodine-131 in the treatment  of thyroid  disorders. 
Experie nce has sh own that the dose  limits and c onstraints  for exposure to members of the public,  family  and 
carers  are unlikely to be exce eded if a patient  is treated with up  to 800 MBq of  iodin e-131 as an outpatient or if  
a patient  is disch arged from a hospital  or clinic when the external  ambient  dose equival ent rate is less than 40 
µSv/h  at 1 m, provid ed that the patient observes some simp le precautions such as restrictions on close proximity 
to other p ersons. 
 
In general, the radiati on dose to p ersons other than t he patient will  depend upon: 
 
a)         the activity and distr ibution  of the radi onuclide retained in the pa tient at the time of disch arge; 
 
b)         the sp ecific exposure rate co nstant of the radi onuclide; 
 
c)         the shie lding provid ed by the patient 's body; 
 
d) the phys ical decay  rate and the biological clearance rate of the radioactive  substance  in the patient 's 
body; and  
 
e)         the time spe nt by such p ersons at rele vant dista nces from the patient.  
 
These r equirements do not sp ecify a different external ambie nt dose equi valent rate f or each 
radiopharmaceutical  even  though the radiation  dose received  by family  memb ers during the course 
of treatment  will depend  on the physical  decay rate and  the biological c learance rate  of the radi oactive  
subst ance in the patient.  Rather,  it is required that the period during which radiation safety  
restrictions should be appli ed should be vari ed to reflect the  different half -lives.  
The doses r eceived by  persons who m ay be close to the  patient for only short peri ods of time (for 
example,  during travel by  public transport or shopping) will depend on the exter nal dose rate and the 
time period  of the  proximity.  Thus,  it is recom mended that the time of travel  by public transport of the  
 disch arged patient  returning home s hould not ex ceed one hour when the pat ient is discharged at  a 
maximum  ambient  dose equivalent  rate of 40 µSv/h at 1 m or, for a radionuclide that emits penetrating 
radiation,  at the maxim um activity  given  in Annex 1 or Annex 2. This  is of particu lar import ance  where  
the  publ ic  transport  involves  confined  adjacent  seating  at  distances  of co nsiderably less than 1 
metre. 
 
C.2      Radionuclides  in sea led forms  
 
C.2.1   Caesium -137 and Iridium -192 
 
Caesium-137 and iridium-192 emit penetrating  gamma radiation  and have significantly  long phys ical half- 
lives (30.1  years and 73.8 days, r espectively).  Sealed so urces of these  radionuclides present  a major radiati on 
hazard if dislodged from the patient or o therwise lost. These so urces are to be r emoved from the patient before  
discharge fr om hospital.  
 
C.2.2   Gold -198 
 
The recom mended maxi mum discharge activity  of 400 MBq for gold-198 corr esponds to an ambient  dose 
equivalent r ate of approximately 25 µSv/h at 1  m (calculated from the unsh ielded g amma dose rate with 
allowa nce made for limited  shielding by the patient 's body).  
 
C.2.3   Iodine -125 and Palladium -103 
 
The ‘no limit’ maximum  disch arge activity for iodine-125 (seale d) contain ed in the 1983 Recommen dations is 
not generally useful.  The major  factor determ ining the external  dose rate from implanted  iodin e-125 and 
palladi um-103 is the depth of implan tation  from the skin surface, which is primarily determined by the 
patient's we ight. Studi es have s hown that, for the com monly admin istered  activity range  of these radi onuclides, 
the ambient dose equiva lent rate at a distance of 1 metre  is less than 0.3 µSv/h  (Smat hers et al. 1999).  
 
The recommended  maximum  discharge  activities  of  2000  MBq  for  iodine-125  and  10  000  MBq  for 
palladi um-103 are exp ected to cover activities adm inistered in c urrent practice. The need for the disch arged 
patient  to limit periods spent in close proximity  to other  persons,  including pregnant wom en, until the 
admin istered  radionuclide has decayed  to at least one-eighth of  the recommend ed maximum  discharge activity  
is emph asized  in the Notes listed in Annex  1. This is due to the high dose  rate at the skin surface  of the  patient  
in the proximity  of the implant.  No activity  limit is necessary  for shielded iodin e-125 or pallad ium- 
103 pl aques or appl icators. 
 
C.3     Radionuclides  in unsealed  forms  
 
C.3.1   Indium -111 
 
The ambient dose  equivalent  rate at 1 metre  from a patient contain ing 400 MBq of indiu m-111 is approximate ly 
25 µSv/h.  
 
C.3.2   Iodine -131 
 
The maxi mum activity  of iodin e-131 in unseal ed forms  at which a patient  may be treated,  as an outpati ent is 
-800MBq in these  Recommendati ons. The  main determin ing factor in this recommen dation  was the external 
dose  rate, but potential  contamination  from excreted  activity  was also considered. A residual patient  activity 
of 800MBq of iodine -131 resul ts in an ambient  dose equiv alent rate in the range 25 - 40 µSv/h  at 1 m, taking 
into account  the shield ing provid ed by the patient's  body.  
  
 
C.3.3   Rhenium -188 
 
The ambi ent dose equivalent  rate at 1 metre from a patient  conta ining 4 000 MBq of rhenium-188 is 
approximate ly 25 µSv/h  (Fox 2002). In  addition,  because of the high energy beta emission,  the potential 
contam ination from excre ted activity needs to be c onsidered. W here excretab le forms are administ ered, the 
time for dischar ge of incontinent  patients  to non-controlled premis es should take into account  the 17 h phys ical 
half-life of this rad ionuclide.  
 
C.3.4   Samarium -153 
 
The r eported ambient d ose equivalent r ate at 1 metre  from patien ts 1-2 hours after the adm inistration of  
3 700 MBq of sam arium-153-EDTMP  is 20-30 µSv/h  (Eary  et al. 1993).  This, taken together with the further 
recomm endation that the patient  should not  be discharged until one, or preferably two, urinary voi ds have 
occurr ed is cons istent with  a rec omme nded maxim um disch arge activity of 4 000 MBq.  
 
C.4      Beta  emitters  (Phosphorus -32, yttrium -90 and strontium -89) 
 
External  dose rate limits  are not applicable to these  radionuclides when  they remain  within the patient's 
body.  There  is minimal  external  dose rate from the activities  normally  administ ered because the beta 
radiati on is absorbed within the patient 's body  tissue. The small  external  dose rate  that does exist in some 
cases is chie fly from bre msstrah lung radiation.  
 
The major concern is from the  excreted activity.  The activity  restrictions for discharge in respect  of urinary 
excreti on and for incontin ent patien ts have been listed in the Notes in Annex 2. Th ese Notes  do not apply  to 
radiopharmaceutical for ms that  are insoluble or  are totally retain ed in the body.  The recommended maxim um 
disch arge activity for phosphorus -32 has been retained at 1 200 MBq,  but the maximum  discharge  activity 
for yttrium -90 has been increased  from 1  200 MBq to  4 000 MBq in  these Recomme ndatio ns. It has been 
shown that  the ambient d ose equiva lent rate at  1 metre from a patient contain ing 4 400 MBq of yttriu m-90, 
when mostly co ncentrated  in the abdom inal o rgans, is approxi mately 5 µSv/h (Smart 20 02). 
 
The recommended maxi mum discharge activity  of 300 MBq for strontium -89 is co nsistent with the relatively 
long physical and  biological half -life of this radionuclide, and shou ld impose  no practical  restrictions si nce the 
admin istered  doses are generally l ess than this.KS 2030:  2019   
  
 
Annex D  
(informati ve) 
 
D.1     Health  effects  of ionizing  radiat ion and standards for control of exposure  
 
It is well known that high dos es of ionizing radiation can cause  harm,  but there  is continuing sc ientific 
uncertainty  about effec ts at low doses. At levels  of dose routinely encount ered by memb ers of the public and 
most  present-day radiati on workers,  there  is little or no epidemiol ogical evide nce of health effects. Radiat ion 
protection standards  recognize that it is not possible to eliminate  all radiati on exposure,  but they do provide 
for a system  of control to avoid unn ecessary exp osure and to k eep doses in the  low d ose ra nge. 
 
Extreme  doses of radiation to the whole body (around 10 sievert  and abov e), received  in a short  period, 
cause so much damage to internal organs and  tissues of the body that vital systems cease to  function and 
death  may result within  days or weeks. Very  high d oses (between about  1 sievert and 10 sie vert), received in 
a short  period,  kill large numbers  of cells,  which  can impa ir the function  of vital organs  and syste ms. Acute 
health  effec ts, such as  nausea, vomitin g, skin and deep tissue  burns, and impairment  of the body’s  ability to 
fight infection  may result w ithin hours, d ays or weeks.  The extent of the dama ge incre ases with  dose.  
 
However, ‘determin istic’ effects  such as these are not observed at doses  below certain threshol ds. By 
limiting  doses to levels below the thresholds, deterministic  effects  can be prevented  entirely. Doses  below 
the threshol ds for determ inistic  effects may cause cellular  damage, but this does not necessarily  lead to 
harm  to the individual:  the effects  are probabilistic or ‘stochastic’ in nature.  It is known that doses above 
about  100 mSv, received  in a short period, lead to an incre ased risk of develo ping cancer later in life. There 
is good epidemiolog ical evidence – especially  from studies of the survivors  of the atomic  bombings –that, for 
several  types of cancer, the risk increases roughly  linearly with dose, and that the risk factor averag ed over 
all ag es and  cancer types  is ab out 1 in 100 for ev ery 100 mSv of dose (i.e. 1 in  10 000 per mSv). 
 
At doses below about 100 mSv,  the evidence  of harm is  not clear-cut. While  some studi es indicate evidence 
of radiati on-induced  effec ts, epidemiol ogical research has  been u nable to establish unequiv ocally that there 
are effects  of statistical  significance at  doses  below  a few tens of millisieverts.  Nevertheless, given  that no 
threshold  for stoch astic effects has be en demonstrated,  and in order to be cautious  in es tablishing  health 
standards, the proportionality between risk  and dose  observed  at higher  doses is presumed to continue throu gh 
all lower levels  of dose  to zero.  This is called the linear, no-thresho ld (LNT) hypothesis and it is made for  
radiation prot ection purp oses only.  
 
There  is evidence  that a dose  accumu lated over a long period c arries less risk than the same dose  received 
over a short period. Exce pt for acciden ts and med ical expos ures, doses  are not normally  received  over s hort 
periods, so that it is appropriate  in determini ng standards for the control  of expos ure to use a  riskfact or that 
takes this into account.  While  not well quantified,  a reduction of the high-dose risk factor by a factor  of two 
has been a dopted  internationally,  so that for radiation protection pur poses  the risk  of radiation-induced fatal 
cancer (the r isk factor) is tak en to be a bout 1 in 20 0 00 per mSv  of dose for the populati on as a who le. 
 
If the LNT hypothesis is correct, any dose carries some risk. Th erefore, measures for control  of exposure  for 
stoch astic effects  seek to avoid  all reasonably  avoidable risk. This is called optimizing  protection. However, 
risk in this sense  may often  be assessed  in terms of risk to a popu lation,  and may not ensure suffic ient 
protection of the individua l. Consequ ently, the optimization a pproach is  underpinned by app lying dose li mits 
that  restrict  the  risk  to  individua ls  to  an  accept able  level.  The  fundam ental  regulatory  philos ophy  is 
expressed in three  principles,  based on  the recomme ndatio ns of the Internati onal Commissi on on Rad iological 
Protecti on (ICRP), w hich may be sum marized as foll ows: 
 
D.2     Justification  
 
Hum an activities that c ause exposure to  radiation  may be permitt ed only if they  do more go od than harm.  
 
D.3     Optimization  of protection  
 
Expos ure to radiati on from justified activities shou ld be k ept as low as re asonably achievable, s ocial and 
economic factors be ing taken into acc ount. KS 2030:  2019   
  
D.4     Limitation of individual  dose  
 
Doses must not exceed the  prescrib ed dose limits.  
 
Determini ng what  is an acceptab le risk for regulat ory purposes is a complex value  judgement. The ICRP 
reviewed  a number of factors  in deve loping its recommen dations, which  have in  general been internationally 
endorsed,  including by the World Health  Organization, the  Internati onal Lab our Organisati on and the 
Internatio nal Atomic Ener gy Agency.  
 
The r ecommended dose limits are  summarized as follows:  
 
D.4.1   Limit  on effective  dose  
 
 
To limit individual r isk For occu pational Expos ure For membe rs of the public  
 
20 mSv per year av eraged over 5 years   
1 mSv in a y ear 
 
In most  situations,  the requirements for limiting  individual risk ensure that doses are below determ inistic 
threshol ds, but for c ases where this does not a pply, the recomm ended limits are as foll ows: 
 
D.4.2   Annual  limit on equivalent  dose  
 
 
Dose Limits Recommended by ICRP  
 
Type of Dose Limit  Limit on Dose 
from  Occupational Exposure  Limit on Dose from  Public 
Exposure  
Effective Dose  20 mSv per year, averaged over 
defined periods of 5 years, with 
no single year exceeding 50 mSv  
After a worker declares a 
pregnancy, the dose to the 
embryo/fetus should not exceed 
about 1 mSv during the 
remainder of the pregnancy  1 mSv in a year  
In special circumstances, a 
higher value could be allowed in 
a single year, provided that the 
average over 5 years does not 
exceed 1 mSv per year  
Equivalent Dose  to the Lens 
of the Eye  20 mSv per year, averaged over 
defined periods of 5 years, with 
no single year exceeding 50 mSv  15 mSv in a year  
Equivalent Dose  to the Skin  
Averaged over 1 cm2  of skin 
regardles of the area 
exposed  500 mSv in a year  50 mSv in a year  
Equivalent Dose  to the 
Hands and Feet  500 mSv in a year   
 
In the case  of occupation al expos ure during  pregnancy, the general principle is  that the embryo  or foetus sh ould 
be afford ed the same level of protection as is required  for a member of the public. For medical work ers, the  Commented [u1]: New annual limits from ICRP 103  KS 2030:  2019   
  
ICRP  recommends that there shou ld be a reason able assurance that foetal dose  can be kept bel ow  1  mGy1)   
during  the  course  of  the  pregnancy.  This  guidance  may  be  generalised  to  cover  all 
occu pational ly exposed pregnant work ers by  keepi ng the foetal dose be low 1 mSv. 
 
1) The gray (Gy) is a unit of radiati on dose.  For X-rays and gamma radiation,  it is essentially equivalent  to 
the sievert.