9 March 2016

Health consequences of the Fukushima accident
Situation of the workers involved in the mitigation activities
carried out at the Fukushima Dai-ichi nuclear power plant
Report on the situation in March 2016

Doses received by TEPCO workers and subcontractors
The main information currently available on the doses received by workers involved in theoperations carried out at the Fukushima Dai-ichi nuclear power plant is that provided by TEPCO,
which has been publishing a monthly report since April 2011. It concerns only the employees of
TEPCO and its subcontractors. The latest report, published on 29 February 2016, concerns 4 687
TEPCO employees and 41 803 employees of subcontractors (i.e. a total of 46 490 employees) who
worked at the Fukushima Dai-ichi power plant between 11 March 2011 and 31 January 2016
(Table I).

Table I: Breakdown of the total doses received by the employees of TEPCO and its subcontractors between 11 March 2011
and 31 January 2016 (report published by TEPCO on 29 February 2016)

Cumulative dose

TEPCO

Subcontractors

Total> 250 mSv

6

0

6

200 – 250 mSv

1

2

3

150 – 200 mSv

26

2

28

100 – 150 mSv

117

20

137

75 – 100 mSv

316

279

595

50 – 75 mSv

328

1 745

2 073

20 – 50 mSv

633

6 410

7 043

10 – 20 mSv

621

5 671

6 292

5 – 10 mSv

496

5 405

5 901

1 – 5 mSv

887

9 584

10 471< 1 mSv

1 256

12 685

13 941

Total

4 687

41 80346 490Maximum (mSv)

678.80238.42-Average (mSv)

22.44

11.61

12.70

The average dose received between 11 March 2011 and 31 January 2016 by these workers is
22.44 mSv for TEPCO employees and 11.61 mSv for subcontractors' employees. As compared to thereport published in February 2015, this shows a slight reduction for TEPCO employees (-0.67 mSv),
but an increase for subcontractors' employees (+0.76 mSv).
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Putting the recorded doses into perspective with respect to exposure limits
At the time of the Fukushima accident, the workers’ exposure limit was 50 mSv per year, and could
not exceed a dose of 100 mSv over five years. Pursuant to Japanese legislation, the exposure dose
limit for an emergency situation was set at 100 mSv at the time of the accident. It was raised to
250 mSv by the order dated 14 March 2011, which entered into force on 15 March 2011, and later
reduced to 100 mSv per year for all workers involved in these emergency works, as from
1 November 2011. The reduction did not apply to the fifty or so workers involved in operations tomaintain reactor cooling functions, for whom the exposure dose limit remained at 250 mSv until
30 April 2012.
Currently, the maximum recorded dose is 678.80 mSv for a TEPCO worker. Since the accident, sixworkers have received a total dose above the 250 mSv limit and 174 have received a total dose of
more than 100 mSv. Analysis of changes in received doses shows that the total number of workers
who received a dose of more than 100 mSv has not changed since April 2012 (150 TEPCO workers
and 24 subcontractors'). Between November 2011 and April 2012, only one worker received a total
dose of more than 100 mSv. Finally, analysis of this data shows that the average internal dose
received by these workers fell from 8 mSv in March 2011 to 0.13 mSv in May 2011. No internal dose
has been recorded since June 2011.
Exposure of other categories of workers
In August 2012, the Japanese authorities sent information pertaining to the exposure of othercategories of exposed workers (fire fighters, policemen, municipal employees, self-defence force
personnel) to the group of experts in charge of drafting the chapter of the UNSCEAR report on doses
to workers. This information was published in the UNSCEAR 2014 report, but is unfortunately very
scattered and not very accurate.
Since the report was published, few studies on the exposure of workers who were affected without
necessarily having worked at the Fukushima nuclear power plant have been published in scientificpapers. One study published in 2014 shows the results of the monitoring set up in July and August
2011 on 101 employees of the municipal general hospital of Minamisoma (located 25 km to the northof the nuclear power plant). The health professionals concerned by this monitoring cared forpatients who were hospitalised or who had come for examinations between 11 and 20 March 2011,
which were when all of the hospitalised patients were evacuated.
Protective measures implemented to minimise the external and internal exposure of these
employees in contact with patients included distributing stable iodine tablets to them on 14 March2011 in order to mitigate the risk of thyroid cancer, and asking them to wear chemical protective
clothing.
According to the results of the measurements taken, caesium-134 was detected in 24 of the 101
employees, but at concentrations corresponding to internal doses of less than 1 mSv. However, thepublication surprisingly makes no reference to possible exposure to caesium-137, which is always
present with caesium-134.
Nevertheless, this publication is noteworthy as it is only the second report since the accident thatanalyses effective doses estimated on the basis of measurements taken from health professionals in
direct contact with potentially contaminated patients. The first study on the same subject,published in 2013, showed the results of measurements performed on five members of an
emergency medical team from Nagasaki University which is specialised in the care of radiation
victims (REMAT). The study concluded that the five persons in question had received doses of lessthan 0.1 mSv due to the incorporation of very low quantities of iodine-131, caesium-134 andcaesium-137.

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Observed effects and health monitoring of workers
Observed effects
To date, at least ten deaths of workers have been recorded, none of which can be attributed to
exposure to ionising radiation according to the information provided by the Japanese authorities:-

Two workers aged between 20 and 30 years died on 11 March 2011 while they were in one of
the Fukushima Dai-ichi buildings flooded after the tsunami.

-

Three workers aged between 50 and 60 years died of heart attack, the first on 14 May 2011,
the second on 9 January 2012 and the third on 22 August 2012.

-

One worker, aged about forty, died of acute leukaemia in August 2011, although he had
never been exposed to ionising radiation before the accident. Between March and August
2011, he received an external dose of 0.5 mSv. Moreover, a whole-body radiation
measurement confirmed the absence of internal contamination on 7 August 2011. Thisadditional information helped in confirming the absence of a cause and effect relationshipbetween exposure to ionising radiation and the leukaemia that caused the death of thisworker.

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One worker, aged about fifty, died of septic shock caused by a retroperitoneal abscess, on 6
October 2011. As was the case of the worker who died of acute leukaemia, this deathcannot be attributed to ionising radiation as the worker had never been exposed before theaccident. He received an external dose of 5 mSv after the accident and a whole-bodyradiation measurement conducted on 9 September 2011 confirmed the absence of internal
contamination.

-

Two workers were fatally injured on the power plant site. The first was buried in sediment
during excavation works in March 2014, the second fell into a storage tank of contaminatedwater in January 2015.

-

A worker, aged about thirty and employed by a subcontractor of TEPCO, died of unknown
causes in August 2015, after having worked for approximately three hours on theconstruction site of an ice wall meant to stop the flow of contaminated water.

Report on the situation of a former TEPCO employee to whom the Japanese health ministry
granted a financial compensation on 20 October 2015
The 41-year-old worker from the city of Kita-Kyushu (Prefecture of Fukuoka) was employed atseveral Japanese nuclear sites between November 2011 and December 2013. In particular, between
October 2012 and December 2013, TEPCO assigned him to the works for covering reactor buildings 3
and 4 of the Fukushima nuclear power plant. Note that this worker was not present at the site
during the initial weeks that followed the accident in March 2011.
In January 2014, the worker was diagnosed as suffering from acute myeloid leukaemia. According to
the dosimetry reports, he had received a dose of 15.7 mSv while working at the Fukushima nuclear
power plant, in addition to a dose of 4.1 mSv received during inspection work conducted for aperiod of three months at the Genkai nuclear power plant in 2012 (i.e. a total dose of 19.8 mSv
between 2012 and 2013).
The worker submitted a claim for compensation to the labour inspectorate to cover his medical
expenses and compensate for his incapacity to work. This compensation was granted by theJapanese government after consulting with a panel of experts under the aegis of the Ministry of
Health, which nevertheless stated that the cause and effect relationship between the exposure of
the worker and the leukaemia that he developed was uncertain.
The decision of the Ministry of Health was based on a government text of 1976, which states thatany worker exposed to an annual dose equal to or greater than 5 mSv, and who developed
leukaemia during the first year following his or her assignment to works likely to expose him or her
to ionising radiation, must receive financial compensation for the damage incurred. The text
specifies that its provisions do not apply if it is proven that the leukaemia developed by the worker
was due to another cause, especially a viral infection. According to this approach, the worker must
always be given the benefit of the doubt in any other situation. These provisions have benefited 13other Japanese workers since they were established in 1976.
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According to the Japanese Ministry of Health, since 2011, eight workers from the Fukushima nuclear
power plant have submitted claims for compensation for pathologies that they believe attributable
to exposure to ionising radiation. Three of the eight claims have been rejected and one was
eventually withdrawn by the worker. The other claims are still being examined.
Health monitoring
A worker health monitoring database has been set up. Each worker, including those who are nolonger involved in on-going operations at the Fukushima Dai-ichi nuclear power plant, benefits froma basic medical check-up that includes eye, ear, chest, cardiovascular and digestive examinations,as well as biological analyses and an evaluation of his or her psychological and psychiatric condition.
Moreover, workers who have received a dose of more than 50 mSv undergo special monitoring todetect the possible occurrence of a cataract. Those who received a dose of more than 100 mSv
undergo additional examinations to monitor the possible onset of thyroid disorders and certain
cancers (lung, stomach, colon).
To the best of our knowledge, no specific and complete assessment of this health monitoring has
been published to date by the Japanese authorities or by TEPCO or its subcontractors (who areresponsible, as employers, for monitoring their employees' health).
The recent IAEA report published in 2015 indicates that TEPCO conducted thyroid ultrasoundexaminations on 672 workers who had received, over the course of 2011, an equivalent dose of
more than 100 mSv, as well as on 1 437 other workers who had received lower doses. The results ofthese thyroid ultrasound examinations showed that there was no significant difference between thetwo groups of workers. This is not very surprising considering the short period of time between theexamination and the exposure (thyroid cancer can take up to several decades to appear after
exposure to ionising radiation), and the fact that the risk of an adult developing radiation-induced
thyroid cancer is extremely low compared to that of exposed children.
Additional information collected following the publication of the WHO and UNSCEAR reports(the information given below comes from the notice published by IRSN in March 2015, as thesituation has not changed since then)Administration of stable iodine to workers
The administration of stable iodine is a preventive countermeasure aimed at saturating the thyroidwith non-radioactive iodine in order to prevent, as far as possible, the accumulation of radioactive
iodine in the thyroid gland in the event of exposure and thereby limit the risk of thyroid cancer inthe long term.
According to the information collected by the working group chaired by an IRSN’s representative aspart of the work of UNSCEAR, approximately 17 500 stable iodine tablets (each containing 50 mg ofiodine) have been distributed since 13 March 2011 to some 2 000 workers, including employees of
TEPCO, the subcontractors, fire fighters, policemen and self-defence force personnel.
No side effect resulting from the administration of stable iodine was observed in the workers
concerned, including the 230 of them who were given stable iodine tablets for more than 14 days,or those who were given more than 20 tablets during the period for which this preventive measure
was implemented. Note that one worker was given a total of 87 stable iodine tablets, without any
noteworthy adverse effect being observed, apart from a temporary disorder of thyroid function(hypothyroidism), which was reported in three workers.
Short-term health risks
In its report published in 2014, UNSCEAR confirmed that no acute radiation syndrome was observedor expected, given that the doses received by even the most exposed workers always remained
below the detection threshold of such effects.

4/5Long-term health risks
The potential long-term consequences of the Fukushima accident on the health of workers wereassessed by the WHO. Its conclusions, published in February 2013, can be summarised as follows:-

It seems unlikely that a statistically significant increase in cataracts will be seen in the few
individuals who received a dose of more than 100 mSv.

-

Workers who received a dose of more than 500 mSv are at an increased risk of long-term
cardiovascular disorders.

-

For two-thirds of the workers (who received low whole-body doses), the risks of cancer are
at a level comparable to fluctuations in the baseline rate.

-

For approximately one-third of the workers (who received moderate doses to the thyroid,
lower doses in the other tissues), the relative increase in thyroid cancer compared to thebaseline rate is estimated to be between 1.4% (workers aged 60 years) and 20% (workers
aged 20 years).

-

For fewer than 1% of workers (those who received the highest doses), the relative increasein leukaemia and thyroid cancer with respect to the baseline rate is estimated at 28% in theyoungest workers.

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For workers who received very high doses to the thyroid (>10 Sv), the risk of a significant
increase in the incidence of thyroid cancer has been estimated, especially in the youngest
workers (attributable lifetime risk of 356 in 10 000).

Based on dose estimations performed using the most recent and consolidated data, UNSCEAR also
evaluated the long-term risks to workers' health in its report published in 2014. Its conclusions,which more or less match those of the WHO, are as follows:-

For the group of 174 workers who received more than 100 mSv (140 mSv on average), two or
three cases of cancer may occur in addition to the 70 or so cancers expected in the absenceof exposure. This increase in the risk of cancer is low compared to natural fluctuations, andhas very little chance of being detected. In the same individuals, one case of leukaemia
could be induced by exposure (relative risk = 1.20 for an average exposure of 140 mSv at
the age of 20 years), but even here, there is little chance of this being detected in an
epidemiological study.

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Approximately 2 000 workers received a dose to the thyroid of more than 100 mGy (averagevalue about 400 mGy). The ultrasound examinations conducted on these individuals arelikely to lead to a substantial increase in the detection of cases making up the baseline rateand in that of radiation-induced cancers, compared to the number of cases expected on thebasis of the reported baseline rate for non-exposed persons. It is not very likely, however,that any increased incidence of radiation-induced cancer will be detectable. On the other
hand, possible cases of hypothyroidism (reduction in the thyroid function) cannot be ruledout.

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For workers who received the highest effective doses, there is a slight probability of excess
cases of circulatory disorders, at least theoretically according to current scientificknowledge.

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The data is not statistically sufficient (too few workers concerned) to make a judgement
concerning a possible increase in the incidence of cataract.

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There are risks of Post Traumatic Stress Disorder (PTSD). A survey conducted two to threemonths after the accident revealed the appearance of such disorders in certain workers.

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