Advisory Note: Change to Operational Intervention Level (OIL) 3 for Nuclear Emergencies 

The Radiation Protection Series (RPS) G-3 Part 2 provides default measurable Operational Intervention Levels (OILs) which could be used to invoke early protective and other response actions. In respect to restricting the ingestion of food early in a nuclear emergency to prevent deterministic and stochastic effects, Table A.1 provided for OIL3 two levels which were: 

  • Ground monitoring – Gamma dose rate of 1 µSv h-1
  • Ground monitoring – Marker nuclide concentration of Iodine-131 or Caesium-137 of 1000 Bq m-2

Providing two different types of ground monitoring measurements for the same protective action may lead to confusion in some cases about which type of measurement regime to implement. 

To bring default OILs provided in RPS G-3 Part 2 into line with International Best Practice OILs for nuclear emergencies, Table A.1 in RPS G-3 Part 2 has been amended and is shown below. OIL3 has removed reference to measuring the marker radionuclide ground concentrations of Iodine-131 or Caesium-137. 

Amended table A.1 RPS G-3 Part 2

Phase OIL Protection action In-plume dose rate Dose rate from deposition Concentration

Urgent (hours to days) 

OIL1a  A Evacuate  500 µSv h-1  500 µSv h-1   
B Shelter  500 µSv h-1  500 µSv h-1 
C Iodine thyroid blocking 

100 µSv h-1 (Adult)
20 µSv h-1 (Childrenb and pregnant women) 


I-131 In-plumec
50 000 Bq m-3 (Adult) 
10 000 Bq m-3 (Childrenb and pregnant women) 

Early (days to weeks)  OIL2 Temporarily relocate   

50 µSv h-1 in first 7 days 
10 µSv h-1 after 7 day

OIL3 Restrict consumption of non-essential local produced, rainwater and milk from animals grazing in the area  1 µSv h-1   
OIL4 Skin decontamination 1 µSv h-1 skin monitoring (at 10 cm from the bare skin) 

Beta skin monitoring 
1000 counts s-1 (at 2 cm from the bare skin) 

OIL7 Restrictions on local produce, milk from grazing animals, rainwater or other open sources of drinking water   

Food, milk, water 
100 Bq kg-1 of 
I-131 or Cs-137 

OIL8 Medical follow-up of thyroid  0.5 μSv h-1 thyroid monitoring (in front of the thyroid in contact with skin)   
a Based on exposure time of 4 hours for in-plume dose rate. Based on exposure time of 7 days for dose rate from deposition
b A child is considered to be under 18 years
c Based on exposure time of 4 hours for in-plume concentration
d Based on exposure duration of 365 days


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