Annex E Intervention levels

On this page Skip this page navigation

(Reference:Paragraph 4.8.8)

1.0 Generic Criteria

1.1 Generic Criteria (GC) are used in the early stages of an emergency, prior to the availability of actual radiation monitoring data, when technical staff in the PEOC Scientific Section undertake dose projection modelling. Generic Criteria values are calculated to reduce the risk of stochastic effects and are expressed in terms of equivalent dose and effective dose.

1.2 Generic Criteria are compared against the dose projections modelled in order to determine the need for implementation of protective measures for the purposes of:

Exposure control
Ingestion control
Population monitoring and medical management
Trade control of foodstuff and other commodities
Transitioning to existing exposure situation^{footnote 14[14]}
Emergency workers and helpers

2.0 Operational Intervention Levels

Operational Intervention Levels (OILs) are used once radiation monitoring data is available to determine the need to implement protective measures. OILs are classified as follows:

Ground Monitoring OILs are used to identify areas (beyond those for response actions that have been taken based on the emergency classification) where the ground deposition of radioactive material warrants protection of the public frequenting or living in the area and restriction of consumption, distribution or sale of food.
Skin Monitoring (gamma and beta) OILs are used to identify individuals with enough radioactive material on the skin to warrant response actions (such as decontamination). Only the public being evacuated or relocated is expected to possibly have sufficient radioactive material on the skin to warrant response actions, but OILs may be used with other members of the public as well.
Food, Milk and Drinking Water OILs are used to confirm and adjust initial restrictions on food, milk and drinking water restrictions that were enacted based on OIL 2.
Thyroid Monitoring OILs are used to identify individuals warranting registration and medical follow-up due to the intake of radioiodine (i.e., evacuated public or those that ingested local produce, country foods^{footnote 15[15]}, milk or rainwater etc.) in areas exceeding OIL 2. These may be used with members of the public as well.

Appendix 1 Generic criteria

Protective Action Strategy	Projected Dose	Protective Actions
Exposure Control Measures	50 mSv (5 rem) in the first 7 days (H_T^{footnote 16[16]})	Iodine Thyroid Blocking
	10 mSv (1 rem) in the first 2 days (E^{footnote 17[17]})	Sheltering
	100 mSv (10 rem) in the first 7 days (E)	Evacuation
Population Monitoring and Medical Management	100 mSv (10 rem) in one month (E)	Medical follow-up (health screening)
Ingestion Control Measures	1 mSv (100 mrem) per year for ingestion of any one of the food/beverage categories (E)	Restriction of distribution and ingestion of potentially contaminated: Drinking water Milk Other foodstuffs and beverages
Trade Control of Foodstuff and Other Commodities	1 mSv (100 mrem) / year (E)	International trade restrictions on non-essential items
Vehicles, Equipment and Other Items	10 mSv (1 rem) per year (E)	Restriction of use for non-essential vehicles, equipment and other items from affected area.
Transitioning to existing exposure situation	20 mSv per year^{footnote 18[18]} (E)	Target dose to enable transition to existing situation.
Emergency Workers and Helpers	50 mSv (5 rem) over the duration of the response. Value may be exceeded voluntarily.	Restriction of activities for individual emergency workers and helpers.

Appendix 2 Operational Intervention Levels (OILs)

1.0 Ground monitoring

OIL	When	Ambient Dose Rate 1 m above ground	Protective Action Strategy	If OIL is exceeded and response action has been taken, proceed to:	If OIL is NOT exceeded, proceed to:
1	Intermediate Phase (within 24 hours following the end of the release)	(1000 µSv/hr)	Evacuation^{footnote 19[19]} IF safe to do so, and ITB, IF directed by MOHLTC (CMOH)	-Registration -Skin Monitoring (OIL 5a and 5b) -Thyroid Monitoring (OIL 8) -Decontam -Medical Screening	Adjust food, milk and drinking water restrictions as per OILs 5, 6 and 7.
2	Intermediate Phase (within 24 hours following the end of the release)	1 µSv/hr	Ingestion control	-Estimate dose from all pathways to determine if medical follow-up is necessary
3	Intermediate Phase (0 – 10 days)	100 µSv/hr for first 10 days after reactor shutdown	Temporary Relocation	-Registration -Temporary Relocation within a month -estimate dose from all pathways to determine if medical follow-up is necessary
3	Intermediate Phase/ Recovery Phases (10+ days to months)	25 µSv/hr later than 10 days after reactor shutdown or for spent fuel	Temporary Relocation

2.0 Skin Monitoring – Gamma and Beta

Complex table with 6 columns and 3 rows, including a header row. The final two columns merge the two data rows into single cells below each header.
OIL	When	Measurement	Protective Action Strategy	If OIL is exceeded and response action has been taken, proceed to:	If OIL is NOT exceeded, proceed to:
4a	Intermediate Phase	Ambient dose rate, 10 cm from bare skin of hand or face * : 1 µSv/hr above background	Decontamination	-Registration -Additional Decon -Thyroid Monitoring (OIL 8) -Decon -Medical Screening -ITB, if advised by MOHLTC -estimate dose to determine if medical follow-up is necessary	OIL 8
4b	Intermediate Phase	Beta count rate, 2 cm from bare skin of hand or face * : 1000 cps	Decontamination		OIL 8

* Measurement must be conducted in an area with a background of < 0.5 µSv/hr.

3.0 Food, Milk and Drinking Water Samples

OIL	When	Foodstuff Category	Gross Alpha (α) Activity	Gross Beta (β) Activity	Protective Action Strategy	If OIL is exceeded and response action has been taken, proceed to:	If OIL is NOT exceeded, proceed to:
5*	Interme-diate Phase	Drinking Water (Tap)	1 (Bq)/L	10 (Bq)/L	Ingestion control -Restriction of distribution and sale of potentially contaminated drinking water, milk and other foodstuffs and beverages	OIL 6 and/or OIL 7 AND -restrict consumption, distribution and sale -estimate dose from all exposure pathways to determine if medical follow-up is necessary	No further restrictions
Milk	1 (Bq)/kg	30 (Bq)/kg
Other Foodstuffs and beverages	3 (Bq)/kg	30 (Bq)/kg

OIL

When

Foodstuff Category

Gross Alpha (α) Activity

Gross Beta

(β) Activity

Protective Action Strategy

If OIL is exceeded and response action has been taken, proceed to:

If OIL is NOT exceeded, proceed to:

Interme-diate Phase

Drinking Water (Tap)

1 (Bq)/L

10 (Bq)/L

Ingestion control

-Restriction of distribution and sale of potentially contaminated drinking water, milk and other foodstuffs and beverages

OIL 6 and/or

OIL 7

AND

-restrict consumption, distribution and sale

-estimate dose from all exposure pathways to determine if medical follow-up is necessary

No further restrictions

Milk

1 (Bq)/kg

30 (Bq)/kg

Other Foodstuffs and beverages

3 (Bq)/kg

(Bq)/kg

* OIL 5 is intended to be used as a rapid screening tool in the field. In certain circumstances, it may be desirable to proceed directly from OIL 2 to OIL 6.

OIL	When	Activity Concentration	Protective Action Strategy	If OIL for EITHER marker is exceeded and response action has been taken, proceed to:	If OIL is NOT exceeded, proceed to:
6	Intermediate Phase	1000 (Bq)/kg of I-131 200 (Bq)/kg of Cs-137 NOTE: both 1-131 and Cs-137 must be assayed	- Ingestion control -Restriction of distribution and sale of potentially contaminated drinking water, milk and other foodstuffs and beverages	OIL 7 AND -restrict consumption, distribution and sale -estimate dose from all exposure pathways to determine if medical follow-up is necessary	No further restrictions

OIL

When

Activity Concentration

Protective Action Strategy

If OIL for EITHER marker is exceeded and response action has been taken, proceed to:

If OIL is NOT exceeded, proceed to:

Intermediate Phase

1000 (Bq)/kg of I-131

200 (Bq)/kg of Cs-137

NOTE: both 1-131 and Cs-137 must be assayed

- Ingestion control

-Restriction of distribution and sale of potentially contaminated drinking water, milk and other foodstuffs and beverages

OIL 7

AND

-restrict consumption, distribution and sale

-estimate dose from all exposure pathways to determine if medical follow-up is necessary

No further restrictions

OIL of 7 for all the rows. Columns 2-6 contain no merged cells.">

OIL	Radionuclide*	Symbol	Drinking water ((Bq)/L)	Milk ((Bq)/kg)	Other Foodstuffs and Beverages ((Bq)/kg)
7	Strontium-89	⁸⁹Sr	300	300	1000
	Strontium-90	⁹⁰Sr	30	30	100
	Ruthenium-103	¹⁰³Ru	1000	1000	1000
	Ruthenium-106	¹⁰⁶Ru	100	100	100
	Iodine-131	¹³¹I	100	100	100
	Cesium-134	¹³⁴Cs	100	300	1000
	Cesium-137	¹³⁷Cs	100	300	1000
	Plutonium-238	²³⁸Pu	1	1	3
	Plutonium-239	²³⁹Pu	1	1	3
	Plutonium-240	²⁴⁰Pu	1	1	3
	Plutonium-242	²⁴²Pu	1	1	3
	Americium-241	²⁴¹Pu	1	1	10

* The radionuclides included here are those which have biological and radiological properties which make them generally expected to provide the most significant dose from the ingestion of drinking water, milk and other foods and beverages following a nuclear emergency.

4.0 Thyroid Monitoring

OIL	When	Measurement	Protective Action Strategy	If OIL is exceeded and response action has been taken, proceed to:	If OIL is NOT exceeded, proceed to:
8	Intermediate Phase	Ambient Dose rate, 1 cm from skin: 2x to 10x background*	Population monitoring and medical management Decontamination	-Registration -ITB, to further reduce uptake if not already taken, AND if directed to do so by MOHLTC (CMOH) -medical screening -estimate dose from all exposure pathways	Registration and record of dose

OIL

When

Measurement

Protective Action Strategy

If OIL is exceeded and response action has been taken, proceed to:

If OIL is NOT exceeded, proceed to:

Intermediate Phase

Ambient Dose rate, 1 cm from skin:

2x to 10x background*

Population monitoring and medical management

Decontamination

-Registration

-ITB, to further reduce uptake if not already taken, AND if directed to do so by MOHLTC (CMOH)

-medical screening

-estimate dose from all exposure pathways

Registration and record of dose

* Must be measured post-decontamination

Footnotes

footnote[14] Back to paragraph Projected dose in the 1st year as a target dose to enable transition to existing exposure situation.
footnote[15] Back to paragraph Country foods are non-commercial foodstuffs which are obtained directly from nature as a result of being foraged, hunted, gathered, fished, or picked.
footnote[16] Back to paragraph H_T = thyroid dose (equivalent dose)
footnote[17] Back to paragraph E = effective dose
footnote[18] Back to paragraph This value is flexible and adjustments may be made depending on feasibility and justifications needed to reach criteria values. If Generic Criteria cannot be met, transition to existing exposure situation may still occur if other Generic Criteria are not exceeded. [From GSR-7]
footnote[19] Back to paragraph If safe evacuation is not possible, the protective action strategies employed would include sheltering and ITB.

Updated: January 19, 2024

Published: September 17, 2021