March 2016

Contamination of Japanese foodstuffs
following the Fukushima accident

Since March 2011, the Japanese Ministry of Health, Labour and Welfare (MHLW) has regularly
published the radionuclide measurement results of foodstuffs produced in Japan on its website1.
The IRSN has systematically analysed all information concerning foodstuffs as and when it became
available.

Summary 2015-2016:
Between March 2015 and February 2016, over 270,000 samples were analysed across the whole ofJapan. These analyses primarily concern foodstuffs from animal sources (≈86%), agriculture (≈10%),
dairy production (≈1%), game (≈0.2%) and other foodstuffs (≈3%). Overall, activities measured inthese foodstuffs are declining, and this decrease can be attributed to the radioactive decay of theradionuclides, various natural processes (caesium migration into the soils, reduction in its
bioavailability...) but also to different anthropogenic measures such as soil decontamination, use ofpotassic fertilisers reducing the transfer of radiocaesiums2, changes in farming practices and even astop to farming in certain areas.
Over this period, less than 0.1% of the measurement results exceed the Maximum Permissible Levels(MPLs)3 to be marketed. These are mainly (≈58%) game meat (wild boar, bear, venison) and certain
specific foodstuffs (≈36%). These MPL exceedances are not confined to the Fukushima prefecture,
and also widely affect the prefectures of Miyagi, Gunma, Tochigi and Nagano.
With very few exceptions, measurement results of samples from agriculture or livestock farming nolonger exceed these levels.
In 2015, despite the notable reduction in activity measured in agricultural production in the
Fukushima prefecture, and the low percentage of measurement results exceeding the MPLs of
100 Bq/kg, the agricultural sector registered a significant decrease in demand, leading tooverproduction and a fall in prices. Sale prices of foodstuffs produced in the Fukushima prefecture
remain, for the most part, below those coming from other prefectures and below 2010 prices. As aresult, farmers' incomes have fallen dramatically, and led to 20,000 of them ceasing their activity.
Only a few products benefiting from a strong brand image, such as asparagus, have got back to sales
prices equivalent to or higher than in 2010.

1

http://www.mhlw.go.jp/english/topics/2011eq/index_food_radioactive.html
These radiocaesiums are caesium-134 and caesium-137.
3
Maximum Permissible Levels for marketing (MPLs): 2000 Bq/kg fresh weight for iodine-131 and 500 Bq/kg fresh
weight for radiocaesium (134+137) up until March 2012, then 100 Bq/kg fresh weight.
2

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March 2016

Reminder of the situation in 2011
The highest levels of contamination in foodstuffs were reached immediately following theradioactive deposits, and affected vegetable foodstuffs whose leaves collected said deposits. At theend of this winter of 2011, only some market gardening production was in progress, in particularleaf vegetables (spinach, lettuce, cabbage...). In the non-evacuated zones most affected byradioactive fallout (notably Iitate-mura and Kawamata-machi, evacuated from April onwards), themassic activity of these highly-sensitive foodstuffs reached several tens of thousands of Bq/kg in
iodine-131 or radiocaesiums (134 and 137). This contamination then rapidly decreased, by 100 to
1,000 times in two to three months. For iodine-131, this reduction is linked to radioactive decay; forradiocaesiums, it is mainly due to plant growth.
The majority of the main crops were at a very early stage of development at the time of theradioactive deposits. Most of the orchard trees were neither in leaf nor in flower. Grain crops were
either sprouting (therefore a long way from grain formation) or had not yet been planted, such as
rice. The plants were therefore only directly affected by radioactive fallout on a small scale, if at
all. Their later contamination occurred via the soil through re-suspension, root transfer or irrigation(in the case of rice). For these reasons, the contamination of the region's main crops was moderatewith regard to the scale of the radioactive deposits.
The contamination of meat and dairy products was limited due to the practice - which is current inJapan - of feeding animals with imported fodder stored under shelter whilst awaiting its
distribution. If cows from the most contaminated non-evacuated territories (such as Iitate or
Kawamata) had consumed local herbage, the radiocaesium content of their milk would haveexceeded 100,000 Bq/L, whereas the maximum observed activities remained 50 to 100 times lower,
only very rarely exceeding 1,000 Bq/L. These activities then quickly decreased, including in themost affected zones: less than 100 Bq/L from April 2011 onwards and, with only a few exceptions,less than 10 Bq/L from June 2011. Again, due to the consumption of imported fodder, meat
contamination - which reached its peak during summer 2011 due to a more progressive transfer of
caesium - was also moderate. Nevertheless, the massic activity of some meat from cattle fed withfodder stored outside at the time of the deposits reached levels of several thousand Bq/kg fresh
weight during July 2011. The destruction of such fodder imposed by the authorities, followed by thedecision to set the permissible radiocaesium level in fodder to 300 Bq/kg dry weight, enabled theprogressive control of the radiocaesium content of livestock meat. With regard to other livestock
products, the analyses carried out on chicken meat and eggs only rarely quantified or detectedtraces of iodine-131 or radiocaesiums, which is consistent with the fact that food consumed bythese animals is often comprised of cereal derivatives harvested the previous summer, andtherefore prior to the accident. The same applies to pork meat and offal even if, only very
occasionally, activities reaching 100 or even 200 Bq/kg fresh weight were observed.
Figure 1 shows that, due to the date of the accident and this practice of importing fodder, thenumber of analysed samples of agricultural and livestock foodstuffs exceeding the marketable levels(different shades of blue) has, since 2011, been very low with regard to the total number of samples

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March 2016

analysed. This number is highest in the Fukushima prefecture (dark blue), followed by theprefectures of Miyagi and Iwate to the north, Tochigi, Gunma and Nagano to the south and southwest. The fact that it reached the most distant prefectures (Gunma, Nagano and Iwate) is linked tosnow and rainfall, particularly during the night of 15-16 March 2011, which led to more significant
radioactive deposits. The contamination of foodstuffs produced in the other prefectures only rarely
exceeded the marketable limits (sky blue and white on the maps), if at all. In the Fukushima
prefecture, only 2.8% of the samples analysed in 2011 exceeded the marketable standard. Mostoften, the activities measured were even more than 5 times lower than these standards.

1548

2014
1006
3325

2011

1933

8734
2452

11

12574
14041
2189

8892

17643

146177

2531
21
4

12025
11935
11758
71981652
203 249
372
236
2707
3926
734
10431596
161
1368
163 499
32
141
23
208
125
89

131
46

2497
7
20
469
473

LégendeNumberof d'analyses
positive analyses
Nombrepositives

95
383

357

58

13145
5211

2295
379 303908

232

821 219
55

87

645

837

1281

193

1-4
5 - 1718 - 32
33 - 71
72 - 487
Total
numberof analyses
Nombred'analyses
totalesFigure 1: Number of analyses of foodstuffs from agricultural production and livestock exceeding
the Maximum Permissible Levels for their marketing in 2011(2000 Bq/kg for iodine-131 and 500 Bq/kg for radiocaesium).

The contamination of agricultural and livestock production therefore remained, on the whole, well
below the marketable standards of 500 Bq/kg fresh weight for radiocaesiums and 2,000 Bq/kg fresh
weight for iodine-131, including within the Fukushima prefecture.

3/14

1539

14205
15345
11356
3431

March 2016

In the case of vegetable foodstuffs, besides the leaf vegetables discussed previously, cases
exceeding the standard mainly concerned Japanese apricots, early fruit harvested from the end of
May onwards whose radiocaesium activity reached several hundred Bq/kg fresh weight, as well as
plants that come into bud early but bear fruit later, such as kiwis or persimmon (figure 2), and dried
fruit4. Trees and shrubs that do not lose their leaves in winter did however intercept radioactive
deposits on a more significant level: this was the case for bamboo (figure 7), tea plants and certain
citrus fruits (yusus in particular). The contamination of bamboo shoots and tea leaves therefore
reached several thousand Bq/kg fresh weight at the most affected sites.

Radiocaesium
activity
in Bq/kg
freshweightfrais
Activitémassiqueen césium
134+137
en Bq/kg
1 000
Norm: 500 Bq/kg
Norme:

Norm: 100 Bq/kg
Norme:

100

10

SM ≈ 8 Bq/kg

1
mars-11

sept.-11mars-12

sept.-12mars-13

sept.-13mars-14

sept.-14mars-15

sept.-15

mars-16

Strawberries
Fraises

Japanese
apricots
Abricotsjaponais

Cherries
CerisesPeachesPêchesApplesPommes

Figs
Figues

Kiwis
kiwis

Pears
PoiresPersimmons
Kakis

GrapesRaisins

Citrus divers
Agrumes

Driedsecs
fruits(chestnuts,
nuts…)
Fruits(chataignes,
noix..)

Figure 2: Radiocaesium activity (Bq/kg fresh weight), above the measurement thresholds5,
in samples of successive harvests of fruit produced across all prefectures.

Most Japanese foodstuffs were therefore relatively spared due to the date of the accident, and it isimportant to underline that, if the accident had occurred three or four months later, many 2011
harvests - fruit and cereal in particular - would have reached extremely high contamination levels
comparable to those observed in leaf vegetables or bamboo shoots.

4

Apart from their low water content, which proportionately increases massic activity, dried fruits often have ahigh potassium content. As caesium is a chemical analogue of potassium, its concentration is also higher.
5
The fact that caesium activity is below the measurement threshold signifies that it was too low to bemeasured. The measurement threshold is not fixed, and depends on measurement conditions: type ofapparatus, duration of the measurement, type and weight of the sample measured. For this report, the term"measurement threshold" thus defined has been chosen over other more technical terms having a particularsignification for specialists, such as "decision threshold" or "limit of detection".

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March 2016

More precisely, figure 3 shows that in 2011, even in the Fukushima prefecture, the number ofsamples of vegetable foodstuffs, milk and livestock meat exceeding the levels was low: 3%, 2.7% et
0.9% respectively.
Numberanalyses
Nombreofd'analyses

Fukushima
Préfecture Prefecturede Fukushima

18000

>NMA
> MPLs< MPLs
<NMA

800

16000

700

14000

600

12000

500

10000

400

8000

300

6000
4000

200

2000

100

0

0

2011 2012 2013 2014 2015 2011 2012 2013 2014 2015
Agricultural
Productionsproducts
agricoles(vegetable)

Farmedmeat
Viandesd'élevage

2011 2012 2013 2014 2015
Milk
Lait

(végétales)

Figure 3: Number of analyses of samples of foodstuffs produced in the Fukushima prefecture over (andrespectively under) the marketable standards: 2000 Bq/kg for iodine-131, 500 Bq/kg for radiocaesium
up until March 2012, then 100 Bq/kg.

Since summer 2011, following the disappearance of iodine-131 through radioactive decay and therapid decline in radiocaesium contamination of market garden vegetables, milk and meat for thereasons mentioned previously, contamination levels of agricultural and livestock foodstuffs havecontinued to decrease. For all foodstuffs, part of this decrease is linked to the radioactive decay of
caesium-134 which, over five years, lost 80%6 of its activity. However, for the main part, thereasons behind this decrease vary according to the type of production and are explained later.

Evolution since 2012
From 2012 onwards, and with only very few exceptions, exceedances of the new Japanese limit of
100 Bq/kg fresh weight only affected:-

wild foodstuffs (game, seasonal mushrooms) or those cultivated in a natural environment(e.g. shiitake mushrooms),-

plant-based foodstuffs that were in leaf in March 2011 at the time of the radioactive fallout:bamboo shoots, tea leaves, aralia and koshiabura shoots, ostrich ferns...

-some agricultural foodstuffs (vegetables) grown in areas located on the outskirts of theevacuated zone, notably rice, buckwheat, soya beans and kidney beans.

In 2015, with only a few exceptions, the foodstuffs exceeding the MPLs only concerned the first two
categories.

6

This 80% fall in caesium-134 in five years is reflected in a reduction of almost 46% in the totalled activities of
the two caesiums, 134 and 137.

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March 2016

Consequently, in order to better summarise the contamination levels of agricultural and livestock
production, it is more relevant, on the one hand, to present the activity measured and its evolution
over the five years and, on the other hand, to present the number of samples for which theradiocaesium content was too low to be measured; i.e. below the measurement thresholds (MTs)applied4.
As the contamination of livestock products can be controlled everywhere via that of the fodder, nolivestock foodstuffs have exceeded the limit of 100 Bq/kg fresh weight in radiocaesiums since mid2012, including in the most affected areas. Caesium content is even predominantly lower than themeasurement thresholds applied by the Japanese, which are themselves 4 to 20 times below themarketable level.
The graphs in figure 4 concern samples of meat, milk and eggs produced exclusively in Date,
Fukushima-shi7, Kawamata, Katsurao, Kori, Minamisoma and Naraha.

Produits
animaux
Animalfoodstuffs

Nombred'analyses
Number ofanalyses

>SM

<SM

600
500

SMmax : 20 (25 en 2012)
SM+ fréquent : 15

400
300

SMmax : 10
SM+ fréquente : 5

200

SMmax : 19
SM+ fréquente : 15

100
0

2012

2013

2014

Meat
Viandes

2015

2012

2013

2014

Eggs
Œufs

2015

2012

2013

2014

2015

Lait Milkde vacheFigure 4: Number of analyses of samples of animal foodstuffs produced in Date, Fukushima-shi, Kawamata,Katsurao, Kori, Minamisoma and Naraha, over(respectively under) the measurement thresholds (SM) indicated.

These graphs show that since 2012 the radiocaesium content of milk and eggs is lower than themeasurement thresholds (<MT in light green): always lower at 10 or 19 Bq/kg respectively(maximum measurement thresholds) and most often lower at 5 or 15 Bq/kg respectively (mostfrequent measurement thresholds). In the case of meats, of the 254 samples from these sites
analysed in 2015, radiocaesium activity could only be quantified once, at around 8 Bq/kg fresh
weight (>MT in dark green).
7

Shi signifies that this refers to the town of Fukushima and not the whole prefecture.

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March 2016

Figure 5 shows that, even for vegetables produced in the aforementioned locations, radiocaesium
content was, for the most part, below 20 Bq/kg fresh weight (highest measurement threshold), or 9
Bq/kg fresh weight (most frequent measurement threshold), i.e. 10 times below the limit. The
highest activity was measured in varieties of cabbage (29 Bq/kg fresh weight), spinach (52 Bq/kg
fresh weight) and broccoli (62 Bq/kg fresh weight). These levels, most often below 9 Bq/kg fresh
weight, are entirely consistent with the underlying radiocaesium contamination of the soils due toroot absorption and the deposit of re-suspended soil dust on leaves. It is likely that thiscontamination of vegetables will decrease only slowly from now on.
The contamination of successive crops of orchard fruits is directly linked to the contamination of
the 2011 harvest and to the stage of development of the trees in March 2011. Figures 2, 5 and 6
show that, each year, Japanese apricots, kiwis and persimmon, as well as dried fruit (chestnuts,
walnuts, ginkgo nuts) present the highest caesium content. Contrary to vegetables or the mainannual crops, this contamination of the 2012-2015 harvests does not result from transfer throughthe soil but from a remanence of tree contamination since March 2011. The proportion ofradioactive deposits intercepted by trees at this time, despite being so low due to the time of year,
was in part maintained by the ligneous parts of the tree, from which it is transferred to new
harvests. Even if it is difficult to know if the decrease observed will continue at this pace, it ispossible, due to the progressive exhaustion of activity "stored" in the tree, that this contamination
is even less frequently measurable (< MT) in harvests over the coming years, including in thoseareas most affected by radioactive deposits. Figure 5 therefore shows that this decrease at themost affected sites can also be observed in the number of analyses returning results above themeasurement thresholds; for fresh fruit, this fell from 85% in 2012 to around 40% in 2014-2015.
Moreover, it must be noted that these activities are effectively the highest of all those shown infigure 2 for all prefectures.

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March 2016

Légumes
et fruits
Fruitsand vegetables

Nombre ofd'analyses
Numberanalyses
600

>SM

<SM

SMmax : 20
(25 en 2012)
SM+ fréquente : 8(20 en 2012)500
SMmax : 20
SM+ fréquente : 9400
SMmax : 25
SMa + fréquente : 8300
SMmax : 13
(20 en 2012)
SM+ fréquente : 8,5

200

100

0
2012 2013 2014 2015 2012 2013 2014 2015 2012 2013 2014 2015 2012 2013 2014 2015 2012 2013 2014 2015
LégumesfeuillesLeafy vegetables

LégumesracinesRootvegetables

Légumes
fruitsFruit vegetables

Fruitsfruits
frais
Fresh

Fruitsfruits
secs
Dried

Figure 5: Number of analyses of samples of vegetables and fruit produced in
Date, Fukushima-shi, Kawamata, Katsurao, Kori, Minamisoma and Naraha, over(respectively
theActivité under)
massiqueen measurement
césium 134+137thresholds
en Bq/kg (SM) indicated.
1 000
Radiocaesium
activity
in Bq/kg
fresh weight
Activitémassiqueen césium
134+137
en Bq/kg

Abricots japonais

1 000
Cherries Cerises

Japanese
Abricotsapricots
japonais

Persimmons
Kakis

100
100

10
10

1
1
mars-11 mars-12 mars-13 mars-14 mars-15 mars-16
mars-11mars-12 mars-13 mars-14 mars-15 mars-11
mars-16 mars-12 mars-13 mars-14
mars-11 mars-12
mars-13 mars-14 mars-15 mars-16

Date-shi

Fukushima-shi

Kawamata-machi

Kori-machi

Minamisoma-shi

Kawamata-machi
Autres préfecturesde Fukushima

Date-shi

Minamisoma-shi

mars-15

mars-16

Fukushima-shi

Kori-machi
Autres préfectures de Fukushima

Figure 6: Radiocaesium activity (Bq/kg fresh weight), over the measurement thresholds, in samples fromsuccessive harvests of Japanese apricots, cherries and persimmon
produced in Date, Fukushima-shi, Kawamata, Kori and Minamisoma.

This remanence of the initial contamination in trees and shrubs exists a fortiori, for those in leaf at
the time of the radioactive deposits in March 2011, such as tea bushes, bamboo and citrus fruits(notably yusus and mandarins).

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March 2016

Figure 7 therefore shows a reduction in activity in bamboo shoots similar to that observed in fruits,
but with a higher overall level of contamination. This level of activity is higher because themeasurements shown on this diagram do not come from the most affected sites in the Fukushima
prefecture but from several prefectures. It is likely that these foodstuffs, liable to exceed
marketable levels, are no longer produced in the zones where deposits were the highest, or are only
produced by way of specific measures (for example new plants) enabling compliance withstandards.

Radiocaesium
activity
Actvitémassiqueen césiums 134+137

10 000Fukushima

Chiba

Ibaraki

Iwate

Miyagi

Tochigi

Gunma

Autres préfectures

1 000

Norme:
100 Bq/kg

100

Seuil de mesure
le plus fréquent10

1
mars-11 sept.-11 mars-12

sept.-12 mars-13

sept.-13 mars-14 sept.-14 mars-15

sept.-15 mars-16

Figure 7: Radiocaesium activity (Bq/kg fresh weight), above the measurement thresholds
in samples from successive harvests of bamboo shoots in several prefectures.

The evolution since 2011 of the contamination of the main cereal crops (wheat, barley, rice) andpulses (kidney beans, soya, buckwheat) varies greatly depending on the species. The radiocaesium
content of wheat and barley, as expected, declined from 2012 onwards, for the most part below 10
Bq/kg fresh weight, i.e. less than a tenth of the marketable limit, including in the non-evacuatedand most-affected areas (figure 8). In 2015, around 1,300 measurements were carried out on rice inJapan, 14 were above the the measurement thresholds including two measurements above the MPLs
(measurement thresholds between 1 and 25 Bq/kg fresh weight; the most frequent measurement
threshold being 10 Bq/kg fresh weight). In the Fukushima prefecture, 18 measurements werecarried out, with seven being above the measurement thresholds including the two measurements
above the MPLs. The small number of measurements carried out on rice produced in the Fukushima
prefecture demonstrates, in all likelihood, the abandonment of this crop in areas where activity inthis foodstuff can still be significant, due to the flooding of paddy fields that leads to a transfer ofradiocaesium from the water to the leaves in addition to root transfer.

9/14

Activité massique(Bq/kg frais)Radiocaesium activity
Activité massique
Activité massiquein Bq/kg fresh weight(Bq/kg frais)(Bq/kg frais)

1000

1000

100

100
10
1
juin-11oct.-12mars-14

juil.-15

Blé Riz
Fukushima-shi, Date, kori, Kawamata, Nihonmatsu
Minamisoma-shi
Koriyama, Motomiya, Otama, Tamura, Miharu, Sukagawa
Iwaki-shiSoma-shiAutres localités de la préfecture de Fukushima
Autres préfectures
Wheat
Rice
(Préf. Miyagi)
BléKurihara
Riz
Fukushima-shi,
Date,
Kawamata,
Nihonmatsu
Fukushima-shi,
Date,kori,kori,
Kawamata,
Nihonmatsu
Minamisoma-shi
Minamisoma-shi
Koriyama,
Motomiya,
Otama,
Tamura,Miharu,Sukagawa
Koriyama,
Motomiya,
Otama,
Tamura,Miharu,Sukagawa
Iwaki-shi
Iwaki-shiSoma-shiSoma-shiAutreslocalitésla préfecturede Fukushima
Autresloalitésde ladepréfecturede Fukushima
Autrespréfectures
Autrespréfectures
Kurihara (Préf. Miyagi)
Fukushima-shi, Date, kori, Kawamata, Nihonmatsu
Minamisoma-shi
Koriyama, Motomiya, Otama, Tamura, Miharu, Sukagawa
Iwaki-shiSoma-shiAutres loalités de la préfecture de Fukushima
Autres préfectures

March 2016

1000
100

10

10
1
juin-11oct.-12mars-14

juil.-15

1
mars-11 sept.-11 mars-12 sept.-12 mars-13 sept.-13 mars-14 sept.-14 mars-15 sept.-15 mars-16
Figure 8: Radiocaesium activity above the measurement thresholds,
in samples from successive harvests of wheat and rice (Bq/kg fresh weight).

The decrease observed for wheat and barley was expected due to a contamination that was
exclusively linked to that of the soil from the 2012 harvest onwards. In the case of soya, thistransfer via the soil is more significant than for cereals and its contamination fell only relatively
slightly between the harvests of 2012 and 2015. In 2015, around 2,300 measurements were carriedout on soya, almost 90% of which were in the Fukushima prefecture; three-quarters of themeasurement results were below the measurement thresholds (≈ 10 Bq/kg fresh weight). The
significant activity measured lies between 1 and 30 Bq/kg fresh weight outside the Fukushima
prefecture, and between 3 and 120 Bq/kg fresh weight within the Fukushima prefecture (twoactivities are over the MPLs: 110 and 120 Bq/kg fresh weight). The results for the 2015 buckwheat
harvest confirm the trend observed in 2014 of a decrease in measured activity. 90% of the results
are now below the measurement thresholds (around 10 Bq/kg fresh weight); activity over thesethresholds lies between 2 and 20 Bq/kg fresh weight with one activity of 76 Bq/kg fresh weight in
the Miyagi prefecture and one of 130 Bq/kg fresh weight exceeding the MPL in the Iwate prefecture.
It is not possible to determine the role of agricultural land decontamination measures or specificmeasures aimed at reducing radiocaesium content (use of potassic fertilisers for example) in thisoverall observed decrease.

The Chernobyl accident had demonstrated that forest products such as mushrooms and game canreach high contamination levels that only decrease slowly over the years. Fukushima has confirmed
this characteristic, extending it to plant-based shoots consumed in Japan (aralia and koshiaburashoots, ostrich ferns) and to cultivated mushrooms (shiitakes). From autumn 2011 onwards, gamemeat (wild boar, venison, black bear, pheasant, water fowl) and seasonal mushrooms frequently

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March 2016

exceeded 100 Bq/kg fresh weight, more occasionally 1,000 Bq/kg fresh weight, in several
prefectures (Fukushima, Tochigi, Gunma...) (see figures 9, 10 and 11 for game). In the case of wildboar meat, values above 10,000 Bq/kg fresh weight were still observed in 2015 in the most affectedsites in the Fukushima prefecture. The downward trend over the four years seems quite weak, inpart due to the radioactive decay of caesium-134.

For these natural or semi-natural products likely to frequently exceed the marketable standards,
including in prefectures other than Fukushima, the measurement results also reproduce theevolution in hunting and harvesting practices. If game is still hunted in the non-evacuated and mostaffected zones, samples of seasonal mushrooms or plant shoots (aralia, koshiabura, ferns...),
reputed for their very high activity, now only rarely come from these areas, and provide information
about contamination levels at sites further away from the Fukushima prefecture and in otherprefectures. In the same way, of the numerous species of mushrooms consumed in Japan, the mostradiologically-sensitive are being progressively identified and picked less, and therefore measured
less. It is therefore difficult to comment on the results in terms of levels of activity and trends. In
2015, of the 1,700 mushroom samples analysed, the activity measured is mainly (75%) below themeasurement thresholds (measurement thresholds between 2 and 25 Bq/kg fresh weight).
Nevertheless, the most sensitive species still show levels of between 120 and 900 Bq/kg fresh
weight, and this activity can be reached more than 100 km from the most affected zones. Very few
measurements (fewer than 2%) have been carried out on species identified since 2011 as being themost sensitive (weeping milk cap, gypsy mushroom, saffron milk cap,...). These species, that are
now well-identified, are picked less. Nevertheless, in October-November 2015, gypsy mushroomspresenting an activity of 460 to 590 Bq/kg fresh weight were picked in the Yamanashi prefecture.
Activity measured in wild plants (aralia, koshiabura, ferns..) is also, on the whole, below themeasurement thresholds (≈75%). The highest activity measured reaches almost 700 Bq/kg fresh
weight in the prefectures of Miyagi and Nagano, almost 400 Bq/kg fresh weight in the Iwate
prefecture, and around 300 Bq/kg fresh weight in Fukushima prefecture.

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March 2016

Nombred'analyses
Numberof analyses

Radiocaesium activity in Bq/kg fresh weight

Préfecturede Fukushima
Fukushima
Prefecture< MPLs
<NMA

1 000

>NMA
> MPLs

100

10

1

2011

2012

2013

2014

2015

Game
meat de gibier
ViandesFigure 9: Number of analyses of samples of game meat hunted in the prefecture of Fukushima that are above(respectively below) the marketable limit: 500 Bq/kg for radiocaesium up until March 2012, then 100 Bq/kg.

Radiocaesium
activity infresh weight
ActivitémassiqueenBq/kg
césiums
134+137 (Bq/kg frais)

10 000Sika Sika
deer
Cerf
Asiannoir
black
bear
Ours
d'AsieCopper pheasantFaisant
scintillant (copper)

Spot-billed
duck
Canardà bectachetéGreen pheasantFaisant
versicolore

1 000

100

10

1

mars-11

sept.-11mars-12

sept.-12mars-13

sept.-13mars-14

sept.-14mars-15

sept.-15

mars-16

Figure 10: Massic activity in radiocaesium, above the measurement thresholds,
measured in samples of game meat from all prefectures.

12/14

March 2016

Radiocaesium
activity enin Bq/kg
fresh weight
Activitémassiquecésiums
134+137 (Bq/kg frais)

100000

10000

1000

100

10

1
mars-11

sept.-11mars-12

sept.-12mars-13

sept.-13mars-14

sept.-14mars-15

sept.-15

Date (Fukushima)

Fukushima-shi (Fukushima)

Hirono (Fukushima)

Iitate (Fukushima)

Kawamata (Fukushima)

Minamisoma (Fukushima)

Nihonmatsu (Fukushima)

Naraha (Fukushima)

Tamura (Fukushima)

Préf. de Fukushima autres localités

Kanuma (Tochigi)

Mashiko (Tochigi)

Nakagawa (Tochigi)

Utsunomiya (Tochigi)

Préf. de Tochigi autres localités

Kimitsu (Chiba)

Otaki (Chiba)

Préf. de Chiba autres localitésAutres préfectures

mars-16

Figure 11: Massic activity in radiocaesium, above the measurement thresholds,
in samples of wild boar meat from all prefectures.

Finally, measurements carried out on "shiitakes" demonstrate the efforts made by producers of thismushroom, of which the number of analyses (≈3,000 in 2015) reflects its importance in Japan. As its
Japanese name indicates, the shiitake (also known in English as the oak mushroom) grows on wood.
In Japan, it is traditionally grown in the undergrowth: cut sections of branches are sown and placedon props. From 2011, its radiocaesium content reached several hundred Bq/kg fresh weight andexceeded 1,000 Bq/kg fresh weight in the Fukushima prefecture (figure 12), notably in the mostaffected sites of Date, Kawamata, Soma and Kawauchi (figure 13). The year after, probably
following specific measures, shiitake contamination fell to around 10 Bq/kg fresh weight at theselocations. In 2012, the highest activity was measured in the prefectures of Gunma, Tochigi, Iwate,
Miyagi and Chiba, in particular at the sites of Chiba-shi, Ichinoseki and Oshu (figure 13). As was thecase the previous year in Fukushima, measures were taken and, since 2013, radiocaesium content atthese sites has also been around 10 Bq/kg and up to 100 Bq/kg at other locations within these
prefectures. At sites such as Chiba-shi and Futtsu-shi, the radiocaesium content of shiitakes,
initially lower, only decreased slightly over the years and, following a slow natural evolution, istoday among the highest. During 2015, of almost 3,000 measurements carried out on shiitakes,
almost half were below the measurement thresholds (from 1 to 25 Bq/kg fresh weight). Activity
measured across all prefectures lies between 1 and 97 Bq/kg fresh weight.

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March 2016

Radiocaesium activity in Bq/kg fresh weight

Activité massique en césiums 134+137 (Bq/kg frais)
10 000
Chiba
IbarakiMiyagi
Tochigi

Fukushima
Iwate
SaitamaAutres préfectures

Gunma
Kanagawa
Shizuoka

1 000

100

10

1

0
mars-11

sept.-11mars-12

sept.-12mars-13

sept.-13mars-14

sept.-14mars-15

sept.-15

mars-16

Figure 12: Massic activity in radiocaesium, above the measurement thresholds,
in samples of shiitakes from all prefectures.

Radiocaesium activity in Bq/kg fresh weight
Activitémassique en césiums 134+137 (Bq/kg frais)

10 000Date-shi (Fukushima)
Kawauchi-mura (Fukushima)
Chiba-shi (Chiba)
Kimitsu-shi (Chiba)
Oshu-shi (Iwate)

1 000

Kawamata-machi (Fukushima)
Soma-shi (Fukushima)
Futtsu-shi (Chiba)
Ichinoseki-shi (Iwate)

100

10

1

0
mars-11

sept.-11mars-12

sept.-12mars-13

sept.-13mars-14

sept.-14mars-15

sept.-15

mars-16

Figure 13: Massic activity in radiocaesium, above the measurement thresholds,
in samples of shiitakes from a selection of sites.

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