REFERENCE LEVELS FOR RADIO ACTIVE MATERIALS IN THE ENVIRONMENT 



Generalised Derived Limits (GDLs) 

GDLs are derived and published by the National Radiological Protection Board (NRPB) for the radioactive isotopes of a small number of elements. GDLs represent a cautionary indicator taking into account the various environmental pathways to man. The limits given below apply to uniform conditions over a year and are based on the limiting age group, which is adults for all foods, except as indicated in the tables. The GDLs for food products are expressed as fresh mass for ingestion, for grass and sediments are expressed as dry mass for external irradiation.




Category 












TERRESTRIAL 
137Cs 
134Cs 
60Co 
65Zn 
131I 







Eggs
3000
2000

400
Freshwater Fish
4000
3000

2000
Fresh water Sediment
20000
8000









Fruit
1000
700

200
Grass 
3000 
2000 

700 
Honey
1700
1200


Meat






Pig





Cattle
2000
1000

600

Sheep
3000
2000

2000

Offal
4000
3000

1000
poultry
2000
2000

1000
Milk Bq/L 
100 
100 

20 
Milk products
1000
900

100
Soil 
1000 
600 


VEGETABLES





Root crop
600
400

100

Other
900
700

400







MARINE






Seafish
700
500
1290
2300
500

Sediment 
5000 
2000 



SHELLFISH





Molluscs 
4000 
3000 
20000 
36000 
2000 

Crustacea 
4000 
3000 
7900 
14200 
2000 



Notes  
Not GDLs but derived limits calculated from NRPB-GS7 and NRPB-GS8. They are for the adult critical group consumers assuming an effective dose equivalent of 1mSv.
For infants aged 1 year.
Not GDLs but derived limits calculated from NRPB-GS7. They are for adult critical group assuming an intake of 25kg/yr and an effective dose equivalent limit of 1mSv.
For children aged 10 years.




Category
Activity (Bq/kg)







238Pu
239,240Pu
241Am
Freshwater Fish
20
200
20
Sediment 



Marine 
100000 
90000 
80000 
Freshwater
400000
300000
300000
Seafish
40
40
40
Shellfish




Molluscs 
200 
200 
200 

Crustacea 
200 
200 
200 
Soil 
5000 
5000 
5000 



Notes  
For infants of 1 year
Only the edible fraction included.
For children aged 10 years.
N.B. These radioisotopes are thought to be the only ones that need to be considered in Southern England at present. Where data are not present this indicates that these radioisotopes are not considered important for the material in question.



Highlighted = samples taken by IWC. 


WT/sermg/03.



Page last updated on: 27/05/2003