I N F O R M A T I O N
F14.v1

CONTAMINATION OF FARM PRODUCE

Since 1987, the contamination of farm
produce has fallen faster than theradioactive decay of caesium
The radioactive decay period for caesium 137 is 30 years, whereas caesium 137
contamination in farm produce is falling about ﬁve times faster. The migration ofcaesium into the depths of the soil combined with a lower level of bioavailability
explains this phenomenon.

REDUCED ACTIVITY IN SURFACE SOIL
In the ﬁrst 20 centimeters down, the noted
decrease in activity occurs faster than thedecrease caused by the radioactive decayof caesium 137 (30 years). Indeed, theradioactive disintegration of caesium 137
combines with natural migration phenomena

and ploughing to drive the radionuclides
down.
Today, only 25 to 50% of the caesium
deposited in the soil in 1986 reaches theroots of plants and vegetables.

Caesium 137 contamination
Bq/m 2

Caesium 137 decay

Rhône Valley( period : 30 years)

00

9,000

018,000

100,000

5,

10,000

04

t

2002
2000
2098
1996
1994
1992
19

1990

88
19

1986

1,000

THE ACTIVITY IN GRASS IS FALLING EVEN FASTER
THAN THAT IN SOIL
Indeed, the caesium ﬁxes to the soil particles
and becomes less accessible to the roots: orit becomes less bioavailable.

This reduction affects contamination activity
in milk.

Caesium 137 contaminationin grass and milk

Bq/Kg
Bq/Kg
fresh
fresh

Auvergne
Auvergne

1010

1010

Alpes-de-Haute-Provence
Alpes-de-Haute-Provence

110.1
0.1

11Grass
Grass
Milk
Milk

0.01
0.01

tt

0.1
0.1
1
19987
871
19989
89
1
19991
91
11999393
119995
95
1
19997
971
19999
99220001
01
22000303
22000505Environment and Response
Division
Philippe Renaud
Tel. +33 (0)4 42 19 96 60
philippe.renaud@irsn.fr

Bq/Kg
Bq/Kg
Bq/l
Bq/l

1199878711998989119991
91119993
93119995
95
11999797119999
99
220001
01
22000303
22000505

CONTACTCaesium 137 contaminationin thymett

www.irsn.org

AFTERMATH

OFTHE

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I N F O R M A T I O N
TO CONCLUDE, THE EVOLUTION IN FARM PRODUCE CONTAMINATION OVERTHE LAST 20 YEARS CAN BE BROKEN DOWN INTO TWO SEPARATE PERIODS■ In 1986, contamination took place on the leaves (direct deposition on the leaves). It was highbut fell quickly.
■ Since 1987, contamination has been through the roots. It is not as high and falls more slowly.
■ The contamination levels from 1986 continued into 1987 for some products. This was the caseof cereals consumed over the period until the next harvest, milk and meat, mainly due to the hay
consumed by animals during winter.

Caesium 137 contamination of farm produce
Bq/kg fresh

1,000

100

10

10,106

04

t

20

2002
20

819
900

619
920

419
921990819819961980.01

Contamination of farm produce is now 10 to 30 times lower than in 1987 and 1,000 to 10,000
times lower than immediately after the deposition from May 1986.

Postal address :Institut de Radioprotection
et de Sûreté Nucléaire
DEI/SESURE/LERCM
B.P. 313115 Saint-Paul-lez-Durance Cedex
Head ofﬁce :77, av. du Général-de-Gaulle
92140 Clamart
Switchboard +33 (0)1 58 35 88 88
Registered at the Nanterre Trade andCompanies Register under no. B 440 546 018

AFTERMATH

OHTHE

CHERNOBYL

ACCIDENTIN

FRANCEIRSN. Communications Department/CPRP; DEI. Printing: OPAG. 2006 F14.v1

Philippe Renaud