SC/F16/JR35

Status of I131, Cs134 and Cs137 in baleen and sperm
whales from the western North Pacific during 20112015
GENTA YASUNAGA AND YOSHIHIRO FUJISE
Institute of Cetacean Research, 4-5 Toyomi-cho, Chuo-ku, Tokyo 104-0055, Japan
Contact e-mail:yasunaga@cetacean.jp

ABSTRACT
From 11 March 2011 onward, radioisotopes (RIs) were released to the marine environment fromthe Nuclear Power Plant in Fukushima following an earthquake and tsunami. To assess thepresence of these RIs in the large whales from the western North Pacific, the I131, Cs134 andCs137 levels in muscle samples of 53 common minke, 16 Bryde’s, 32 sei and 3 sperm whales
from JARPNII surveys were measured in the period of JARPNII (2011-2015). I131 was notdetected in muscle samples of all large whales, except for two minke whales from off Kushiro in2012. Ranges of Cs134 + Cs137 concentrations in minke, sei, Bryde’s and sperm whales wereND-31, ND-9.8, ND-7.1 and ND-0.59 Bq/kg wet wt., respectively. The radioisotope levels inall whales examined have been decreasing since 2011, and were also extremely
lower than the radiation safety threshold for humans. Therefore, risk of acute toxicity
levels for I131, Cs134 and Cs137 would be extremely low in the large whales from the western
North Pacific.
KEYWORDS:
SPERM
WHALE;RADIOISOTOPES; FUKUSHIMABALEEN

WHALES;CESIUM;

IODINE;INTRODUCTION
On 11 March 2011, the Great East Japan Earthquake and following tsunami destroyed the Nuclear Power
Plant in Fukushima. This accident led to release of large amounts of radioactive materials. The mainradioactive isotopes emitted were I131, Cs134, Cs137, Nb95, Ce144, Ru103, Ru106, Sr90, Pu239 andPu240 etc., and the total amount was in the order of 14 × 1018 Becquerels (Yamashita and Suzuki, 2013).
Radiation exposure from I131 fallout causes cancer of thymus, and Cs134 and Cs137 cause solid cancer
and leukemia in humans.
Highly migratory, top predator species, such as common minke (Balaenoptera acutorostrata), sei (B.
borealis), Bryde’s (B. edeni) and sperm whales (Physeter macrocephalus) have been exposed to theseradioactive materials in the western North Pacific, and especially young minke whales pass throughcoastal waters of east Japan. Also, the 2011 IWC/SC annual meeting suggested that concentrations ofradionuclides, especially caesium-137, should be included under second objective, “monitor
environmental pollutants in cetaceans and the marine ecosystem” in the JARPNII programme (IWC,2012).
In the present study, we monitored I131, Cs134 and Cs137 concentrations in muscle to assess health offour large whale species from the western North Pacific, and we compared these data to safety thresholdfor humans.
MATERIALS AND METHODS
Muscle tissue samples of 53 minke, 32 sei, 16 Bryde’s and 3 sperm whales taken form the western North
Pacific were analyzed for I131, Cs134 and Cs137 concentrations (Bq/kg wet wt.) (Table 1). All samples
were stored in polyethylene bags at -20°C until analysis.
The samples were sent to the National Research Institute of Fisheries Science (Kanagawa, Japan) before
2013 and the Marine Ecology Research Institute (Chiba, Japan) after 2013 for analyses of the I131, Cs134
and Cs137 radioisotopes. Analyses were performed in each institute according to the analytical manual
for radioactive materials in foods in emergency (Ministry of Health, Labour and Welfare, 2002).

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The correlations between Cs134 + Cs137 concentrations in muscle of whales and the research years
were assessed by Spearman rank test (Zar, 1999) in minke whales in sub-areas 7, 8 and 9, off Kushiro andoff Sanriku, sei whales in sub-areas 8 and 9 and Bryde’s whales in sub-areas 7, 8 and 9. A p value of lessthan 0.05 was considered to indicate statistical significance in all tests. These statistical analyses wereexecuted using SPSS ver.11 for Windows (SPSS Co. Ltd.).

RESULTS AND DISCUSSION
Table 2 shows the I131, Cs134 and Cs137 concentrations in muscle of minke, sei, Bryde’s and sperm
whales. I131 concentrations in only two minke whales from off Sanriku among all whales were detected.
Ranges of Cs134 + Cs137 concentrations in minke, sei, Bryde’s and sperm whales were ND-31, ND-9.8,
ND-7.1 and ND-0.59 Bq/kg wet wt., respectively. Significant correlation of concentrations of Cs134 +Cs137 in whales and research years were observed in minke whales from off Sanriku, sei and Bryde’s
whale in sub-areas 7, 8 and 9 (p<0.05), whereas no significant correlations were observed in minke
whales from sub-areas 7, 8 and 9, and off Kushiro. However, maximum levels in Cs134 + Cs 137
apparently decreased with research years in minke whales from off Kushiro and the sub-areas 7, 8 and 9samples.
Internal exposure to radioactive iodine causes thyroid cancer over 50-200mSv in human children(Brenner et al., 2011; Yamashita and Suzuki, 2013). Concentrations of I131 in muscle of only two minke
whales from off Sanriku were about 0.5 Bq/kg, whereas this RI was not detected in almost all whales
tested. This detected level can be converted to about 0.44μSv (0.5Bq/kg × 40kgBW ×0.022 = 0.26μSv
in human children), suggesting that thyroid cancer risk for the whales may be extremely low. And also,internal exposure to radioactive cesium does not cause solid cancer under 100mSv in humans (Yamashitaand Suzuki, 2013). The maximum radioactive Cs value detected in all whales was 31 Bq/kg. This levelcan be converted to about 24 μSv (31Bq/kg × 60kgBW ×0.013 = 24.18μSv in human), suggesting thatsolid cancer risk for the whales may also be extremely low. Therefore, risk of acute toxicity for I131,
Cs134 and Cs137 would be extremely low in the large whales from the western North Pacific.

REFERENCES
Brenner, A.V., Tronko, M.D., Hatch, M., Bogdanova, T.I., Oliynik, V.A., Lubin, J.H., Zablotska, L.B.,
Tereschenko, V.P., McConnell, R.J., Zamotaeva, G.A., O’Kane, P., Bouville, A.C., Chaykovskaya,L.V., Greenebaum, E., Paster, I.P. Shpak, V.M. and Ron, E. 2011. I-131doseresponse for incident
thyroid cancers in Ukraine related to the Chernobyl accident. Environ. Health Perspect. 119:933–939.
International Whaling Commission. 2012. Report of the Scientific Committee. J. Cetacean Res. Manage.
(Suppl.) 13: 1-73.
Ministry of Health, Labour and Welfare. 2002. The analytical manual for radioactive materials in foods inthe emergency. http://www.mhlw.go.jp/stf/houdou/2r9852000001558e-img/2r98520000015cfn.pdf
Yamashita, S. and Suzuki, S. 2013. Risk of thyroid cancer after the Fukushima unclear power plant
accident. Respir. Investig. 51:128-133.
Zar, J.H. 1999 Biostatistical analysis, 4th ed., Prentice Hall, New Jersey, USA, 663pp.

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Table 1. Sample list of common minke, sei, Bryde’s and sperm whales taken from JARPNII surveys
and used in the present study
AreaSpecies

YearnOff shore

common minke whale2011

3(2M1F)

Average
7.1(6.22012

6(5M1F)

6.9(4.8-7.87)

sei whale

Bryde's whale

sperm whale
Off Sanriku

Off Kushiro

common minke whale

common minke whale

Body length (m)Range- 8.11)

2013

1(1M)

7.5

2011

3(2M1F)

14.0(13.6-14.7)

2012

10(4M6F)

13.7(12.4-15.2)

2013

5(2M3F)

14.0(13.5-14.3)

2014

7(4M3F)

14.0(12.7-15.1)

2015

7(2M5F)13.5(11.7-15.2)

2011

3(3F)

13.2(13.0-13.4)

2012

3(2M1F)12.0(10.7-13)

2013

4(3M1F)12.7(11.2-13.8)

2014

3(1M2F)12.8(12.5-13.2)

2015

3(2M1F)

12.3(11.1-13.2)

2012

2(1M1F)10.1(8.7-11.5)

2013

1(1F)

7.4

2012

6(2M4F)

4.9(4.0-5.92)

2013

3(1M2F)

4.6(3.7-5.28)

2014

4(3M1F)

6.1(4.7-7.47)

2015

5(3M2F)

6.2(4.7-8.05)

2011spring

6(3M3F)

7.2(5.9-8.11)

2011autumn

6(3M3F)

5.8(4.3-7.28)

2012

5(3M2F)

5.8(5.1-7.38)

2013

5(1M4F)

7.1(5.1-8.68)

2014

3(2M1F)

6.8(5.5-8.21)

3

SC/F16/JR35
Table 2. Concentration values of I131, Cs134 and Cs137 (Bq/kg-wet) in muscle of common minke, sei,
Bryde’s and sperm whales taken from JARPNII surveys
AreaOff shore

Speciescommon minkeYear
2011whale2012

sei whale

2013
2011

2012

2013

2014

2015

Bryde's whale

2011

2012

2013

11NP-M001
11NP-M002
11NP-M049
12NP-M001
12NP-M008
12NP-M011
12NP-M038
12NP-M045
12NP-M072
13NP-M002
11NP-SE014
11NP-SE043
11NP-SE071
12NP-SE001
12NP-SE003
12NP-SE009
12NP-SE012
12NP-SE024
12NP-SE043
12NP-SE047
12NP-SE051
12NP-SE064
12NP-SE068
13NP-SE001
13NP-SE005
13NP-SE022
13NP-SE055
13NP-SE091
14NP-SE001
14NP-SE007
14NP-SE026
14NP-SE044
14NP-SE05714NP-SE070
14NP-SE082
15NP-SE001
15NP-SE011
15NP-SE022
15NP-SE035
15NP-SE049
15NP-SE060
15NP-SE080
11NP-B007
11NP-B039
11NP-B047
12NP-B001
12NP-B008
12NP-B011
13NP-B001
13NP-B002
13NP-B021
13NP-B024

4I131

Cs134

Cs137

Cs134+137

ND
ND
ND
<0.54
<0.69
<0.53
<0.48
<0.69
<0.58
<0.465
ND
ND
ND
<0.50
<0.61
<0.54
<0.74
<0.51
<0.62
<0.50
<0.59
<0.65
<0.53
<0.303<0.437<0.304<0.468<0.328<0.359<0.425<0.400<0.417<0.481<0.424<0.389<0.415<0.441<0.370<0.361<0.403<0.418<0.347
NDND
ND
<0.57
<0.53
<0.43
<0.407<0.365<0.373<0.347

ND
9.1
ND
3.1
2.4
1.4
<0.53
1.2
4.5
0.556
NDND
ND
1.6
3.3
<0.55
1.3
2.8
1.3
0.93
<0.62
<0.69
<0.63
0.425
<0.462<0.304<0.4680.702<0.432<0.585<0.599<0.594<0.480<0.465<0.402<0.492<0.448<0.418<0.499<0.605<0.460<0.3602.92.9ND
1.6
<0.62
1.3
<0.395<0.376<0.422<0.350

ND
12ND
4.5
3.9
1.7
<0.94
2.1
7.1
1.57
ND
ND
ND
2.36.5
<1.1
2.6
3.4
2.1
2
<0.86
<1.0
1.1
1.05
0.794
1.03
1.17
1.49
0.764
0.589
0.842
0.595
<0.6090.714
0.812<0.5360.95<0.4580.75<0.480<0.557<0.373
3.6
4.2
ND
2.6
1.7
1.6
0.691
0.931
0.95
1.11

ND
21
ND
7.6
6.3
3.1
ND
3.3
11.6
2.1
ND
ND
ND
3.99.8ND
3.96.2
3.4
2.93
ND
ND1.1
1.5
0.79
1
1.2
2.2
0.76
0.59
0.84
0.6
<1.1
0.71
0.81
<1.00.95<0.88
0.75<1.1'<1.0
<0.73
6.5
7.1
ND
4.2
1.7
2.9
0.69
0.93
0.95
1.1

SC/F16/JR35
Table 2. Continued
Area
Species

Year
2014

2015

sperm whale

2012
2013

OffSanriku

common minkewhale

2012

2013

2014

2015

OffKushiro

common minkewhale

2011spring

2011autumn

2012

2013

2014

14NP-B001
14NP-B007
14NP-B019
15NP-B001
15NP-B015
15NP-B025
12NP-S001
12NP-S003
13NP-S001

I131<0.474<0.387<0.491<0.332<0.390<0.381<0.55<0.51<0.411

Cs134<0.508<0.445<0.511<0.395<0.326<0.380<0.46<0.54<0.376

Cs137<0.516<0.4920.589<0.404<0.441<0.439<0.82<0.79<0.363

Cs134+137
<1.0
<0.94
0.59
<0.80
<0.77
<0.82
ND
ND
<0.74

12NPCS-M001M
12NPCS-M005M
12NPCS-M008M
12NPCS-M012M
12NPCS-M031M
12NPCS-M055M
13NPCS-M001M
13NPCS-M005M
13NPCS-M016M
14NPCS-M001M
14NPCS-M013M
14NPCS-M020M
14NPCS-M029M
15NPCS-M001M
15NPCS-M002M
15NPCS-M013M
15NPCS-M018M15NPCS-M019M

<0.32
<2.80
<0.68
<0.66
<0.48
<0.68
<0.4120.495
0.483<0.448<0.395<0.468<0.496-<0.33
<0.51
6.2
5.2
<0.52
6.1
<0.4481.1
1.17<0.448<0.396<0.4790.362<0.329<0.455<0.384<0.427<0.394

0.7
<0.90
10
7.9
<0.91
9.3
0.6
1.79
2.34
0.725
0.614
0.648
0.584
<0.496<0.520<0.445<0.457<0.5170.7
ND1613ND
15
0.6
2.9
3.5
0.73
0.61
0.65
0.95
<0.83
<0.98
<0.83<0.88<0.91

11NPCS-M001M
11NPCS-M004M
11NPCS-M007M
11NPCS-M011M
11NPCS-M016M
11NPCS-M017M
11NPCK-M001M
11NPCK-M019M
11NPCK-M032M
11NPCK-M039M
11NPCK-M043M
11NPCK-M050M
12NPCK-M001M
12NPCK-M006M
12NPCK-M027M
12NPCK-M040M
12NPCK-M041M
13NPCK-M001M
13NPCK-M028M
13NPCK-M041M
13NPCK-M052M
13NPCK-M053M
14NPCK-M001M
14NPCK-M014M
14NPCK-M035M

ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
<0.44
<0.55
<0.57
<0.59
<0.539<0.437<0.465<0.442<0.457<0.416<0.318<0.357<0.483

ND
ND
14ND
9.3
ND
ND
1.2
<0.52<0.53<0.58<0.588<0.388<0.436<0.481<0.426<0.467<0.274<0.446<0.470

ND
ND
17ND
15ND
ND
2.8
1.8
<0.89
0.9
<0.901<0.4511.21<0.4760.48
0.47<0.302<0.528<0.438

ND
ND
31
ND
24
ND
ND
17.6
12.55.4
ND
21.64
1.8
ND
0.9
ND
ND
1.2
ND
0.48
0.47
0.48
ND
0.85

5SC/F16/JR35

Cs 134 +137 (Bq/kg)

40

Common minke whale
Off Kushiro●：subarea 7

2011 spring30
2011 autumn

201002010

2011

2012

2013

Cs 134 +137 (Bq/kg)

40

20102011

2012

2013

Cs 134 +137 (Bq/kg)

40

2014

2015

2016

Common minke whale
Offshore●：subarea 7○：subarea 8△：subarea 930201002010

2011

2012

2013

40
Cs 134 +137 (Bq/kg)

2015

Common minke whale
Off Sanriku●：subarea 73002010

2014

2015

2016

Sei whale
Offshore●：subarea 7○：subarea 8△：subarea 930201002010

2011

2012

2013

40
Cs 134 +137 (Bq/kg)

2014

2014

2015

2016

Bryde’s whale
Offshore●：subarea 7○：subarea 8△：subarea 930
201002010

2011

2012

2013

Year2014

2015

2016

Figure 1. Concentrations of Cs 134+137 in muscle of common minke, sei and Bryde’s whales taken fromthe western North Pacific from 2011 to 20156