Environment International 64 (2014) 17–27

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Environment International
journal homepage: www.elsevier.com/locate/envint

Global and local cancer risks after the Fukushima Nuclear Power
Plant accident as seen from Chernobyl: A modeling study forradiocaesium (134Cs & 137Cs)
Nikolaos Evangeliou a,⁎, Yves Balkanski a, Anne Cozic a, Anders Pape Møller babLaboratoire des Sciences du Climat et de l'Environnement (LSCE), CEA-UVSQ-CNRS UMR 8212, Institut Pierre et Simon Laplace, L'Orme des Merisiers, F-91191 Gif sur Yvette Cedex, France
Laboratoire d'Ecologie, Systématique et Evolution, CNRS UMR 8079, Université Paris-Sud, Bâtiment 362, F-91405 Orsay Cedex, Francea r t i c l e

i n f oArticle history:
Received 10 September 2013
Accepted 29 November 2013
Available online xxxx
Keywords:
CancerCaesium-137
Fukushima
LNT-model
Death risksa b s t r a c t
The accident at the Fukushima Daiichi Nuclear Power Plant (NPP) in Japan resulted in the release of a large number of ﬁssion products that were transported worldwide. We study the effects of two of the most dangerous radionuclides emitted, 137Cs (half-life: 30.2 years) and 134Cs (half-life: 2.06 years), which were transported acrossthe world constituting the global fallout (together with iodine isotopes and noble gasses) after nuclear releases.
The main purpose is to provide preliminary cancer risk estimates after the Fukushima NPP accident, in terms ofexcess lifetime incident and death risks, prior to epidemiology, and compare them with those occurred after the
Chernobyl accident. Moreover, cancer risks are presented for the local population in the form of high-resolution
risk maps for 3 population classes and for both sexes. The atmospheric transport model LMDZORINCA was used
to simulate the global dispersion of radiocaesium after the accident. Air and ground activity concentrations havebeen incorporated with monitoring data as input to the LNT-model (Linear Non-Threshold) frequently used inrisk assessments of all solid cancers. Cancer risks were estimated to be small for the global population in regions
outside Japan. Women are more sensitive to radiation than men, although the largest risks were recorded
for infants; the risk is not depended on the sex at the age-at-exposure. Radiation risks from Fukushima weremore enhanced near the plant, while the evacuation measures were crucial for its reduction. According to ourestimations, 730–1700 excess cancer incidents are expected of which around 65% may be fatal, which are very
close to what has been already published (see references therein). Finally, we applied the same calculations
using the DDREF (Dose and Dose Rate Effectiveness Factor), which is recommended by the ICRP, UNSCEAR
and EPA as an alternative reduction factor instead of using a threshold value (which is still unknown). Excess
lifetime cancer incidents were estimated to be between 360 and 850, whereas 220–520 of them will be fatal.
Nevertheless, these numbers are expected to be even smaller, as the response of the Japanese ofﬁcial authorities
to the accident was rapid. The projected cancer incidents are much lower than the casualties occurred from theearthquake itself (N20,000) and also smaller than the accident of Chernobyl.
© 2013 Elsevier Ltd. All rights reserved.

1. Introduction
Accidental releases of radioactive material have occurred several
times at NPP with Chernobyl and, recently, Fukushima to be the most
severe events (Fesenko et al., 2004; Terada et al., 2012). Modelingtools may prove very efﬁcient in assisting the authorities in decisionmaking and preventing extended radiological exposure of the population (WHO, 2012). However, environmental contamination cannot
be prevented and may affect the public indirectly. High doses havedeleterious consequences for humans, including, but not exclusively,enhanced cancer occurrences. At doses greater than 50–100 mSv⁎ Corresponding author at: Laboratoire des Sciences du Climat et de l'Environnement(LSCE), CEA-CNRS-UVSQ, Institut Pierre et Simon Laplace, L'Orme des Merisiers, F-91191
Gif sur Yvette Cedex, France. Tel.: +33 1 6908 1278; fax: +33 1 6908 3073.
E-mail address: Nikolaos.Evangeliou@lsce.ipsl.fr (N. Evangeliou).
0160-4120/$ – see front matter © 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.envint.2013.11.020(protracted exposure) or 10–50 mSv (acute exposure), direct epidemiological evidence demonstrates increased risk for some cancers. Nevertheless, the situation is much less clear for very low radiation doses,
although the risks of low-dose radiation are of societal importancedue to medical tests, occupational exposure, radiological terrorism etc.
(e.g. Brenner et al., 2003). Once radionuclides are released, they may
enter the body directly by ingestion and inhalation causing DNA andcell damage, and cancers known to have a mutational basis. Another irradiation factor is external exposure, which might be chronic or acute.
The ﬁrst includes irradiation from radionuclides deposited at the
ground's surface, whereas the second during fallout transport.
The tsunami that struck the Fukushima Daiichi NPP in northeasternJapan in 2011 caused signiﬁcant fuel meltdown along with hydrogen
explosions after the cooling system failed. Several radionuclides werereleased into the atmosphere and dispersed over long distances. The
emissions lasted for about 40 days (whereas additional discharges of

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cooling water to the Paciﬁc Ocean are still ongoing) and traces of radionuclides were detected worldwide (Diaz Leon et al., 2011; Hong et al.,2012; Masson et al., 2011). Two years after the accident, the cancer
risk to the population remains unknown, as no epidemiological studies
are available yet. In fact, the effects of radiation to humans can beassessed several years later through the cancer registration system ofJapan, when death certiﬁcates are available and a statistic analysis ispossible.
The present study provides estimates of the worldwide healtheffects from the Fukushima NPP accident, in terms of excess lifetime
cancer incident and death risks prior to epidemiology. We have usedthe LNT-model, also used by the World Health Organization (WHO,2013), to quantify the health impact with respect to radiogenic cancer
diseases. The main goal is to evaluate our model's response by addressing the global health risks from the accident in Japan and comparing
them with the ﬁndings of the WHO (based on measurements). This isvery important if one takes into account that a large number of NPPs
already exists (437) presenting an increasing trend in the future (seeFig. S1, Supplementary Information—SI). A sensitivity analysis is also
attempted by assessing how the different model resolutions affect theresults (presenting risks after Chernobyl). In addition, we provide
high-resolution maps of excess lifetime cancer incident and deathrisks to the local population of 2010, in contrast to the region-speciﬁc
estimates reported by Ten Hoeve and Jacobson (2012). However,
because many researchers argue on the use of the LNT-model for suchcalculations, we present the same excess lifetime risks using a DDREF
of 2 as a reduction factor instead of a threshold (still uncertain), below
which no visible effects on humans can be observed. In addition, we
present age- and sex-speciﬁc LAR (Lifetime Attributable Risk) and LFR(Lifetime Fractional Risk) maps for the local population of Japan. Deaths
from Fukushima are expected to be fewer than from Chernobyl by morethan an order of magnitude due to lower total emissions, lower deposition rates over populated land and more precautionary measures taken
immediately after the accident (Ten Hoeve and Jacobson, 2012).
2. Methodology
2.1. Source emission and model general characteristics
The aerosol module INCA (INteractions between Chemistry andAerosols) is coupled to the general circulation model (GCM), LMDz, developed at the Laboratoire de Météorologie Dynamique in Paris, and theglobal vegetation model ORCHIDEE (ORganizing Carbon and Hydrology
In Dynamic Ecosystems Environment) (LMDZORINCA) (see also Szopa
et al., 2012). The gas phase chemistry part in the model is describedby Hauglustaine et al. (2004). Aerosols and gasses are treated in thesame code to ensure coherence between gas phase chemistry and aerosol dynamics as well as possible interactions between gasses and aerosol particles. The model was used in the simulations for the Chernobyl
and Fukushima accidents achieving a maximum horizontal resolutionof 2.5° in longitude and 1.27° in latitude (regular grid). However, theGCM also offers the possibility to zoom over speciﬁc regions bystretching the grid with the same number of grid-boxes. In the present
study the zoom version was used for Europe (Chernobyl runs) and Asia
(Fukushima runs for the local health assessment) achieving a resolutionof 0.45° × 0.51°. On the vertical plane, the model uses sigma-p coordinates with 19 levels extending from the surface up to about 3.8 hPa corresponding to a vertical resolution of about 300–500 m in the planetary
boundary layer (ﬁrst level at 70 m height) and to a resolution of about
2 km at the tropopause (with 7–9 levels located in the stratosphere).
Each simulation lasted until the end of the year, which is a sufﬁcient period for the 99.5% of 137Cs to be deposited (Brandt et al., 2002; Paatero
et al., 2012). As regards to the emissions of 137Cs, the inventories(36.7 PBq) reported by Stohl et al. (2012) were adopted estimatedby inverse modeling using the CTBTO (Comprehensive Nuclear Test
Ban Treaty Organization) global measurement network. For the

Chernobyl accident, the emissions reported by De Cort et al. (1998)
were used.
LMDZORINCA accounts for emissions, transport (resolved and subgrid scales), photochemical transformations, and scavenging (dry deposition and washout) of chemical species and aerosols interactively in the
GCM. Several versions of the model are currently available dependingon the envisaged applications with the chemistry–climate model.
The model runs in a nudged mode (using the ERA40 Re-analysis
data – 6 h wind ﬁelds – by the European Centre for Medium-Range
Weather Forecasts, ECMWF, 2002) with a relaxation time of
10 days for the regular grid, whereas for the zoom version relaxing
to 4.8 days in the center of the zoom and to 10 days outside(Hourdin and Issartel, 2000).
The radioactive tracer 137Cs (half-life = 30.2 years) was inserted as
an inert tracer within the model. The behavior of 137Cs in the atmosphere is strongly related to its chemical form as it may be released in
the atmosphere in gaseous form or adsorbed onto particles. Here, it isassumed that mostly 137Cs behaves as an aerosol and as such it is treatedin the model. In fact, this is true, as it has been reported that over 80% of
the 137Cs emitted in the atmosphere during accidental releases is in theform of particulates (Potiriadis et al., 2011; Ritchie and McHenry, 1990;
Sportisse, 2007; Yoschenko et al., 2006). The partitioning between
gaseous form and particles and the size distribution of aerosols strongly
affects dry deposition and scavenging, which is presented in detail in
the SI (p. 3–6). We examine radiocaesium isotopes (134Cs and 137Cs)
because, together with 131I and 133Xe (half-lives: 8.02 and 5.24 days),they have been found to be the most abundant in the global fallout
after Fukushima (Christoudias and Lelieveld, 2013; Kristiansen et al.,2012; Stohl et al., 2012). Moreover, they emit gamma rays and can substitute potassium in living organisms; hence, they are among the mostdangerous.
2.2. Risk calculations to humans
The LNT-model of human exposure (SI, p. 6) was used to calculate
radiological health effects, similar to the Chernobyl accident (EPA,
1999; ICRP, 2005). The model assumes that each radionuclide's disintegration has the same probability of causing cell transformation, and thateach transformed cell has the same probability of developing a cancer
tumor. Although the LNT-model has been employed extensively in radiation safety (NRC, 2006; UNSCEAR, 2010), several arguments about its
validity and response at low doses still remain unresolved. For example,
Cuttler (2010) stated that low doses of radiation might improve healthin living organisms including humans, whereas Tubiana et al. (2009) argued for its use based on radiation biological and experimental data.
This is mainly because epidemiological studies have only considereddoses above 100 mSv showing a statistically signiﬁcant increase instochastic cancer risk, although at doses below 100 mSv signiﬁcanceor lack there-of has not been observed. On the other hand, supportersof the LNT-model claim that the difﬁculty in detecting and attributing
a small number of cancers to low doses does not necessarily indicatethat there is an absence of risk at these doses (Hoffman et al., 2012).
Nevertheless, given that the NRC (Nuclear Regulatory Commission)and the WHO accept the LNT hypothesis for health assessments, we
adopted it in the study. The main purpose for that was mainly tocompare our results to what the WHO has already published(WHO, 2013).
A radiogenic cancer risk model deﬁnes the relationship between
radiation dose and the subsequent force of death (or incident) attributable to that dose. Death risk is deﬁned as an estimate of the risk to an average member of the population of dying from cancer over its lifetime.
Incident risk is the risk of experiencing radiogenic cancer during aperson's lifetime, whether or not the cancer is fatal. Inhalation exposure,ground-level external exposure, and atmospheric external exposure
pathways were considered for 134Cs, 137Cs, and their decay products
134
Ba and 137mBa, respectively (ICRP, 1995). Health effects from

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radionuclide ingestion pathways were only calculated for the Japanese
population based on monitoring data reported by the WHO (2012). In
these calculations, it is assumed that the local population exclusively
consumes food produced in areas where food monitoring was implemented and the deposition of 137Cs decreases only by radioactive
decay. The respective contribution of 134Cs deposition rates in eachgrid cell and time step was also included assuming a 134Cs/137Cs isotopic
ratio of 0.92, based on CTBTO observations following the Fukushima
NPP accident (Christoudias and Lelieveld, 2013). However, consideringthat a full range monitoring system has been established in Japan after
the radioactive releases, it is expected that this pathway might beoverestimated here as all the foodstuffs are measured for radioactive
substances and are handled according to international and national
standards. On the other hand, in coastal regions of Japan located far
from the large population centers it is expected that ﬁshermen might
consume food products without prior radioactivity monitoring. Taking
into account that cooling water from the damaged reactor is stilldischarged to the ocean, several inhabitants may consume contaminated foodstuffs. This practically means that the model may underestimate
the risk coming from food ingestion.
LAR was calculated, which speciﬁes the probability of a prematureincident of a cancer attributable to radiation exposure in a representative member of the population (Kellerer et al., 2001; Thomas et al.,
1992; Vaeth and Pierce, 1990). For a given dose, LAR is the additional cumulated probability of having a speciﬁc cancer up to the age of 89 years(89 years is the average death age of the Japanese population, WHO,2013). It relies on the use of a risk model derived from the epidemiological literature and is a classical risk indicator in the ﬁeld of radiation protection. LAR speciﬁes for a person exposed to a low dose the radiationrelated excess probability for a fatal cancer. If, as is usual, the concept
is applied to an exposed population, it speciﬁes the expected numberof fatalities, and such numbers – when they are not linked to the number of spontaneous cases – can be misleading. It is then more conducive
for a realistic perception of risk to refer to a relative number. Such anumber is obtained if LAR is scaled to the lifetime spontaneous cancer
death (or incident) in the reference population leading to the LFR. All
the relative functions used to calculate the LAR and LFR probabilities
can be seen in SI (pages 6–11). They have been calculated for both
sexes (males and females) and ages of 1 year (infants), 10 years (children) and 20 years (young adults) in different locations of Japan andfor all solid cancers.
Moreover, the excess lifetime cancer death and incident risk fromeach exposure pathway (below for inhalation and ingestion) was calculated by the following equation (Ten Hoeve and Jacobson, 2012):
Rs ¼

XX
i

j

(

"

"

Pij 1−exp −rs

##)

X 
Ir Ai; j;t;s −Ath;d ; 0

19fruits, soft fruits, milk, beef, lamp, ﬁsh and mushrooms weretaken from the WHO (2012).
External ground deposition and external atmospheric exposure were
calculated using the same equation without the respective internal
rates (Ir). The respective incident risks for 134Cs (ground deposition, atmospheric exposure) were adopted from EPA (1994). The shielding effect inside structures was also taken into account by assuming a 30% reduction
in exposure from particulate 134Cs, 137Cs and their decay products for 12 heach day when people are assumed to be indoors (Price and Jayaraman,
2006). However, the effect of the vertical migration of radiocaesium (inground based exposure pathway) was not taken into consideration andthe only temporal reduction of the radionuclides occurred via radioactive
decay. It has been found that radiocaesium resided in the atmosphere for
2–3 months after the accident (Long et al., 2012; Masson et al., 2011;
McMullin et al., 2012; Paatero et al., 2012); therefore, external atmospheric and internal inhalation exposures were negligible after 3 months
and only ground-level exposure was signiﬁcant the following years.
3. Results
3.1. Deposition, annual doses from radiocaesium and comparison withmeasurements
The global deposition of radiocaesium from Fukushima is shown in
Fig. 1 for 2011. The maximum value at the relevant scale is 40 kBq m−2

ð1Þ

t

where
Rs
Pi,j
rs

Ir
Ai,j,t,sAth,dis the total number of lifetime cancer deaths or incidents due
to species s over all times t and grid cells i,j,is the 2010 population (or 1990 population for the estimatesof Chernobyl) in each grid cell i,j (NASA, 2013),
is the relative cancer death or incident risk coefﬁcient for species s expressed in units of Bq−1 (or m2 Bq−1 and m3 Bq−1 forground-level and external atmospheric exposure) from EPA(1994),
is the inhalation or ingestion rate (17.8 m3 day−1, EPA, 1999
and 0.75 kg day−1, Table S1 (SI)),is the species concentrations in each grid cell i,j at time t, andis the threshold concentration below which no health effectoccurs (for the LNT-model is zero by default). For the calculation of the risks from food ingestion, monitoring data for the
foodstuffs cereals, green vegetables, root vegetables, orchard

Fig. 1. Global cumulative deposition of radiocaesium (134Cs and 137Cs) after the Fukushima
NPP accident at the end of 2011. Annual effective dose from radiocaesium exposure due toinhalation, surface deposition and fallout transport.

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as it is the threshold value of radioactive contamination (IAEA, 2009). The
highest deposition was found in the pixel of Fukushima (in the range of
MBq m−2), where deposition exceeded the contamination limit affecting
an area with more than 9 million inhabitants. In the West USA the deposition was found between 100 and 500 Bq m−2 decreasing to the East.
For the South-west USA, Wetherbee et al. (2012) reported that the deposition of 137Cs was 30–240 Bq m−2 and 2–46 Bq m−2 for 134Cs, which isin the same order as in our calculations (Fig. 1). The same investigators
reported a deposition of 137Cs in Alaska to be 16–27 Bq m−2 and around
55 Bq m−2 for 134Cs similar to those presented here (50–100 Bq m−2).
In the rest of the US they measured 137Cs between 1 and 45 Bq m−2
and 134Cs between 1 and 3 Bq m−2, which are close to ours (50–200 Bq m−2), although we slightly overestimate. Low deposition ofradiocaesium was observed in Europe with the respective values to be
20–100 Bq m−2, which are slightly overestimated comparing to what
has been recorded. For example, Povinec et al. (2012) measured a deposition between 2 and 114 Bq m−2 for 137Cs and up to 100 Bq m−2 for134
Cs in Slovakia, Barsanti et al. (2012) reported a radiocaesium deposition of 0.3 Bq m−2 in La Spezia (Italy), Carvalho et al. (2012) reported
1 Bq m−2 of radiocaesium in Portugal, Evrard et al. (2012) found 134Cs deposition near Paris (France) to be around 2 Bq m−2, Kritidis et al. (2012)
observed 137Cs deposition in Athens (Greece) around 10 Bq m−2, andPham et al. (2012) assessed that the deposition of radiocaesium in
Monaco is few Bq m−2. The model also predicted identically low depositions over Asia (0.5–50 Bq m−2), which are comparable to observations (e.g. 3 Bq m−2 in Korea, Kim et al., 2012). Further comparison ofambient 137Cs concentrations from the model and the CTBTO network
can be found in the SI (Fig. S4).
Regarding dosimetric calculations, there were assumptions about
the implementation of protective measures and food consumption
based on options that are more likely to overestimate than to underestimate the radiation exposure. For example, the assumption that all
foodstuffs were obtained from the market where monitoring occurs(given that this is a rural prefecture, a lot – perhaps most – of the foodstuffs may derive from gardens and farms); also, the assumption that all
people in Fukushima prefecture consumed only food produced in Japan.
Therefore, some possible dose overestimation may have occurred. In
the present study, dosimetric calculations were applied using environmental modeling and food monitoring data, rather than direct humanmeasurements. The experience from Chernobyl has shown that when
whole-body counting was used to determine human exposure, theresulting doses were much lower (IAEA, 2006). Monitoring data ofinternal and external exposures at Fukushima during the last 2 years
show that, in some cases, the doses reported here might be slightly
higher (Akahane et al., 2012; Kamada et al., 2012; Monzen et al.,2011; Tsubokura et al., 2012). Applying the gridded data of the 2010global population in the excess lifetime risk calculations, we estimatethat more than 90% of the Japanese residents received an annual
effective dose from radiocaesium of less than 0.5 mSv, whereas therest received up to 5 mSv. However, it is expected that this percentage
exposure to the highest levels is even smaller when taking into accountthe interventions that can reduce radiation exposure (e.g. evacuation)
including more stringent standards and remedial actions (e.g. cleanup
of buildings, remediation of soils and vegetation, treatment of agricultural ﬁelds, waste management) that cannot be accounted for in themodel.
3.2. Global health risks of low-level radiation exposure
Radiation exposure can be acute over short time-scales (accidents)or chronic (occupational exposure). In general, protracted exposures
are associated with lower risks than acute ones for the same totaldose, both for cancer and other endpoints (Little et al., 2009). Goodevidence of an increase in cancer risk is shown for acute doses of greaterthan 50 mSv. As expected from basic radiobiology, the doses above,
where statistically signiﬁcant risks are seen, are somewhat higher

for protracted exposures than for acute ones (Boice, 2012). The dose–
response relations used in the present study are depicted in Fig. S3(SI). The linear relation is a possible descriptor of low-dose radiation oncogenesis, although different endpoints may well exhibit differently
shaped dose–response relations. About one ﬁfth of people worldwide
and one third of people in industrialized regions are diagnosed withcancer during their lifetime (IARC, 2008). Radiation can induce cancers
that are indistinguishable from cancers resulting from other causes.
Most population-based cancer risk estimates come primarily from theJapanese atomic bomb survivors. In addition, there are several othersources of radiation exposure of which useful epidemiological data are
available (e.g. past accidents, medical and environmental exposures).
Increased radiation-related risks have been observed for leukemia(Tsushima et al., 2012), and for a large number of solid cancer sites(Douple et al., 2011).
The global excess lifetime death risks from radiocaesium for the
Fukushima accident (applying zero threshold in Eq. (1)) are depicted
in Fig. 2 for the gridded population of 2010, together with the respective
ones just after the Chernobyl accident in 1986 (for the population of1990). Finally, an estimation of the contribution of both accidents isshown for the global population of 2010 for an average life expectancyof 69 years assuming physical decay and indoor occupancy to be
the reducing factor after Chernobyl. The pathways of deposition, airsubmersion and inhalation were taken into consideration, whereas foodingestion was assumed to be negligible in these global estimates.
Caesium-134 was included in radiocaesium estimations for the Chernobyl
accident using the respective isotopic ratio 134Cs/137Cs equal to 0.5 certiﬁed by measurements (De Cort et al., 1998). The accident in Japan presents a negligible radiological risk, both in terms of cancer incidents anddeaths, with a peak in the adjacent regions of the NPP (Fig. 2) as approximately 80% of the released radionuclides were deposited in the ocean
and only 20% across populated regions (Christoudias and Lelieveld, 2013).
The number of projected deaths, however, is still considerably smaller than the estimated ones after Chernobyl (Fig. 2), due to the larger
emissions after Chernobyl (139 PBq of radiocaesium after Chernobyl,
69.7 PBq after Fukushima) and also because most of them were deposited over continental regions (90%). Deﬁnitely, the most dangerous exposure pathways remain inhalation and ingestion as internal factors,
although deposition may play an important role as a chronic parameter.
An example of chronic exposure is given in Fig. 2, where health risks
from radiocaesium were estimated from both accidents. Although we
account for radioactive decay and indoor occupancy, there is stillenhanced excess lifetime cancer incident and death risk for the global
population of 2010 for the areas around the nuclear site of Chernobyl.
4. Discussion
4.1. Importance of model resolution
Fig. 3 depicts excess lifetime risks from radiocaesium (applying zerothreshold) after the Chernobyl accident from air-submersion, inhalationand deposition exposures. The vast majority of the incident and deathrisks were estimated in the nearby countries of the NPP, although significant ones were observed in Sweden and Finland and Greece and Turkey
following the fallout transport and the prevailing precipitation patterns(Brandt et al., 2002; Evangeliou et al., 2013). However, when a betterresolved version of our model was used (0.45° × 0.51°) much lower
levels of danger were recorded limited to the restricted exclusionzone. In fact, this is very accurate since the dose rates observed in thisarea just after the accident were such that no human would be able tosurvive for many days without taking a lethal dose of radiation. For
example, the radiation levels near the reactor building have been estimated to be 5.6 Roentgens per second (R s− 1), equivalent to morethan 20,000 Roentgens per hour (lethal dose: 500 Roentgens over5 h) (Medvedev, 1990). Approximately 50% of the lifetime risk was
due to inhalation, whereas the rest was caused by air-submersion andN. Evangeliou et al. / Environment International 64 (2014) 17–27

21

Fig. 2. Global excess lifetime cancer incident and death risks from radiocaesium (134Cs and 137Cs) after the Fukushima accident applied to the global population of 2010. In contrast,
the same excess lifetime risks have been estimated after the Chernobyl accident for the global population of 1990. Also, the impact of both accidents is presented for the population of2010 assuming that the only reducing parameters after Chernobyl are the physical decay of the radionuclides and the indoor-human occupancy.

deposition. Ingestion was not taken into consideration due to the lack ofstatistical data. In total, excess lifetime risks obtained using both model
resolutions for the Chernobyl accident differ by about 25%, with the lowest observed using the highest resolution. Therefore, a possibility ofoverestimation should be considered in such studies increasing thetotal uncertainty of the calculations.
4.2. Health risks of the Japanese population
In order to be more accurate and efﬁcient in this preliminary metricsof radiation risk without causing panic to the population, the resolution of
0.45° × 0.51° was used over Asia. LAR and LFR for all solid cancers were
estimated for infants (1 year old), children (10 years old) and young
adults (20 years old) of both sexes and are illustrated in Fig. 4 andFig. S5 (SI). LAR expresses the probability of a premature incident of aradiation-related cancer. The concept of LAR has an implicit “cumulative”
nature derived from the way LAR values are calculated: as an integrationof the risk that could be attributed to radiation exposure, arising on a
year-per-year basis (excluding the latency period). In this context, LAR
is an “extra” lifetime risk that is added to an already existing Lifetime
Baseline Risk (LBR) (SI, page 9). The LFR reﬂects the relative increase incancer risk that could be attributed to radiation exposure.
LAR in Japan is higher in female infants (N 14 in 10,000), and lower
for 10-year-old male children (b4 in 10,000) for the areas of approximately 100 km northeast of the Fukushima NPP, and in general higher
for females as shown in Fig. 4. Inhalation exposure contributed to LAR
for approximately 46%, whereas 29% was due to deposition, 22% was
due to ingestion, and 3% was due to the external air submersion(Fig. 5). These results are in good agreement with reported values by
the WHO (2013). If the inhalation exposure pathway is excluded, risks

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N. Evangeliou et al. / Environment International 64 (2014) 17–27

Fig. 3. Excess lifetime cancer incident and death risks from radiocaesium (134Cs and 137Cs) after the Chernobyl NPP accident in Ukraine (1986) using 2 different resolutions in the model.
Using the highest resolution more than 25% lower risks are obtained.

are higher for 1-year-old infants and 10-year-old children than for 20year-old adults. However, given that the inhalation rate for infants andchildren is much smaller (5.2 m3 day−1 for infants, 15.28 for children
and 22.18 for adults), LAR was calculated to be higher for adults.
LFR follows the same patterns (Fig. S5) and is highest for adult andinfant females in the restricted area of the NPP (1.1%), whereas it falls
below 0.2% (minimum) in the nearby Tokyo metropolitan areas (andin the rest of Japan) with these values being lower than those reportedby the WHO (2013). Very small LFR for all solid cancers indicates thatthe actual number of “extra” cancer cases is likely to be small; therefore,
the impact in terms of public health would be limited. The exposuresthat contribute more to the risk are again the internal ones (43% forinhalation and 28% for food ingestion) (Fig. 5).
No acute effects of radiation exposure such as acute syndrome orskin burns have been recorded in Japan, since they are usually observed
after exposure to high doses. Given the range of prevailing doses, no increase in the frequency of cataracts, circulatory diseases or any other tissue reactions is expected for the general population. In general, cancer

incident and death rates increase with age. Even a modest absolute
excess reﬂects a large relative risk in children, as seen by the LAR and
LFR. Women tend to be at a greater risk of cancer from a given unit
dose of radiation than men and the sex difference is largely independent
on the age-at-exposure (Figs. 4 and S4).
4.3. Excess lifetime incidents and deaths with and without a threshold
Fig. 6 (upper panels) and Figs. S6–S7 (SI) depict the excess lifetime
cancer incident and death risks, from all types of exposure inradiocaesium in Japan. They have been estimated for the Japanese
population of 2010, which was the last available dataset of population
density. We estimate 730–1700 excess cancer incidents, of which
450–1040 might be fatal worldwide similar to those reported by Ten
Hoeve and Jacobson (2012) (15–1100 incidents and 24–1800 deaths
from exposure to 134Cs, 137Cs and 131I) with more than 90% to occur inJapan (a relevant comparison can be found at SI, Table S2). It is apparent
in Fig. 6 (two upper panels) that the fatal incidents are accumulated

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23

Fig. 4. LAR for both sexes (males and females) of 1 year (infants), 10 years (children) and 20 years (young adults) in different locations of Japan for all solid cancers.

where the exclusion zone has been set up, which shows very well thevalidity of the modeling results. However, we expect these values tobe much lower, because of the evacuation measures, because thesechanges were not taken into account in the population data of 2010. A
rough estimation made by setting population to zero in the pixels of
the exclusion zone and spreading it to the westerly-adjoined pixels

Fig. 5. Relevant exposure contribution to the calculated risk for the Japanese population. Internal exposure pathways contribute more (inhalation: 46% in LAR, 43% in LFR—food ingestion:
29% in LAR, 28% in LFR) together with the cumulative deposition of radiocaesium (22% in LAR, 26% in LFR).

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N. Evangeliou et al. / Environment International 64 (2014) 17–27

Fig. 6. Excess lifetime cancer incidents and deaths from radiocaesium exposure (air-submersion, deposition, inhalation, food-ingestion) in Japan. The upper two panels depict the incidents
without any threshold in Eq. (1), whereas in the bottom two panels the DDREF recommended by the ICRP, UNSCEAR and EPA has been applied to our estimates.

showed that the lifetime deaths and incidents would be decreased by
45%. Nevertheless, this is only a scenario as it is unknown where the population moved after evacuation and also how many people remained near
the plant and for how long (e.g. plant workers, ﬁremen etc.).
Given that many researchers do not accept the LNT-hypothesis
for risk calculations believing that there must be a threshold dose(see Subsection 2.2), below which no visible effects can be observed,
we perform some additional estimations for the excess lifetime risk
calculations applying the DDREF. In general, epidemiological estimatesof overall and site-speciﬁc cancer risks (except for leukemia) related toradiation exposure are statistically consistent with a linear dose–response relationship (ICRP, 2005). For the same reasons that data restricted to low doses tend to be uninformative about radiation-related
excess risk, this apparent linearity does not rule out, on statisticalgrounds, the possibility of increased, decreased, or even absent excess
risk per unit dose at very low doses. For those reasons the linearmodel estimated excess risks are often divided by a DDREF at low
doses and low dose rates as a method to substitute the uncertain
threshold. Speciﬁcally, the ICRP notes in Publication 103 (ICRP, 2007)
that “the Commission considers that the adoption of the LNT-model
combined with a judged value of a dose and dose rate effectivenessfactor (DDREF) provides a prudent basis for the practical purposes ofradiological protection, i.e., the management of risks from low-dose radiation exposure”. Although a threshold has been identiﬁed to be somewhere between 5 and 25 mGy (ICRP, 2005), the exact dose still remains
unknown. Therefore, a DDREF of 2 should be applied for radiation protection purposes, whereas the UNSCEAR (UNSCEAR, 1993) recommended
that the chosen DDREF should be applied to chronic exposures at dose
rates less than 6 mGy h−1 averaged over the ﬁrst few hours, and toacute exposures at total doses less than 0.2 Gy. This recommendation
was also adopted by the EPA (EPA, 1999). The resulting excess lifetime incidents and deaths from radiocaesium exposure in Japan after applying
the DDREF to our calculations can be seen in Fig. 6 (two bottom panels)
and also in the SI (Figs. S8–S9). The total incidents are now calculated tobe between 360 and 850 (incidents) and between 220 and 520 (deaths),
which are in the lowest level if compared with the range that Ten Hoeve
and Jacobson (2012) have reported. However, as discussed previously,
these amounts are expected to be even lower due to the evacuation measures taken immediately after the accident.
The highly contaminated zone close to the NPP is of the order of two
pixels in our simulations and only few grid-cells represent the whole ofJapan. The spatial resolution of our simulations may not be sufﬁcient toallow detailed analysis of the consequences in the immediate vicinity ofFukushima (perhaps, a local/regional model would be more appropriate).

N. Evangeliou et al. / Environment International 64 (2014) 17–27

However, basic preliminary insights can be gained about what has
happened in Japan and how the local population might be affected bythis accident, although epidemiological studies are mandatory for moredetailed discussions. Another point is the associated uncertainty of theresults, which is deﬁnitely high. This is mainly because of the uncertainty
in the source term (still researchers and Japanese authorities argue on theexact amounts released), the prevailing depositional ﬁelds (European
Centre for Medium-Range Weather Forecasts, ERA40 Re-analysis data—
6 h wind ﬁelds were used), the LNT-model (see Subsection 2.2) andalso the DDREF used to perform a more realistic assessment (EPA,
2011). Given that epidemiological studies will be published in several decades from now (when death certiﬁcates will be available), such model
assessments present an overview of the current and future situation.
5. Conclusions
The atmospheric transport model LMDZORINCA was used to record
the impact of radiocaesium (134Cs and 137Cs) on the global and Japanese
population from the recent accident in Fukushima Daiichi NPP (Japan)that occurred after a large earthquake (off the coast) and the subsequent tsunamis that attacked the east coast. Most of the released
radiocaesium was deposited in the nearby areas of the NPP and the
Paciﬁc Ocean, whereas low impact was recorded in North America
and even lower in Eurasia. Nevertheless, the model is deﬁnitely very
close to the measurements reported elsewhere.
In order to evaluate the magnitude of the accident, the impact on the
global population was estimated using the LNT-model and speciﬁcallythe excess lifetime cancer incident and death risks after Chernobyl and
Fukushima (for the relevant population density). The accident in Japan
presents a negligible radiological risk, both in terms of cancer incidents
and deaths, with a peak in the adjacent regions of the NPP much lower
in comparison to the Chernobyl accident. This is due to the different
emissions (almost double in Chernobyl) and also because most of theradiocaesium released from Fukushima was deposited in the World
Ocean.
The impact on the local population was assessed using the LAR and
LFR variables estimated from the LNT-model. The risk was higher for
female infants, and lower for 10-year-old male children for the nearby
areas of the NPP. In general, women are more sensitive to radiation
exposure, while the sex is completely independent from the age-atexposure. Moreover, the relevant lifetime cancer death and incident
risks were calculated for the Japanese population of 2010 showing
approximately 730 to 1700 cancer incidents and 450 to 1040 deaths
from exposure to radiocaesium. However, many researchers haveaddressed their doubts about the extrapolation of the risk into low
doses using the LNT-hypothesis. For that reason we performed thesame computations of excess lifetime cancer risks applying the DDREF
on our results. Cancer incidents were estimated to be between 360
and 850, of which 220–520 might be fatal, although these numbers
are expected to be lower due to the evacuation decided by the ofﬁcial
authorities. According to the French Institute of Radioprotection and
Nuclear Safety (IRSN, 2012) approximately 73 radionuclides werereleased after Fukushima. Therefore, one might argue on the low impact
concluded in our study claiming that only radiocaesium has been studied
instead of the 73 radionuclides emitted. However, this is not expected toaffect very much the present results, as (i) most of the radionuclides
emitted constitute the local fallout (they are more refractory and heavier); hence, they were deposited where population was moved (WNA,
2013), and (ii) it has been found that the worldwide fallout consists
mainly of Cs and I isotopes (short-lived) and noble gasses (short-lived)(e.g. Masson et al., 2011). A study for thyroid cancer in Fukushima has
showed that the average risks of cancer incident and death due to 131I
for infants were estimated to be 3 × 10−5 and 0.2 × 10−5, respectively,
lower than the annual risks of trafﬁc accidents, naturally occurring radioactive material, and environmental pollutants such as diesel exhaust particles (Murakami and Oki, 2012). In contrast, another study (Yasumura

25

et al., 2013) showed that the overall (total radioactivity) death rate has
been found to be 2.4 times higher in 2011 than in 2010 suggesting thatthe impact of a disaster on the excess death of institutionalized elderly
is most signiﬁcant in the immediate aftermath, but has a lasting impact
due to continuing changes in nutritional, hygienic, medical and generalcare conditions.
Since Chernobyl, long-term psychological effects including depression, anxiety, fear, and unexplained physical symptoms have beenfound to increase (Bromet, 2012; Bromet et al., 2011). Similar effects
are likely to occur in evacuees after Fukushima together with widespread mistrust of the Japanese government. In addition the accident
also resulted in economic losses of billions of dollars due to cleanup
costs and reduced economic activity in areas affected by radioactivity(Brumﬁel and Fuyuno, 2012). The Chernobyl accident had a costthrough May 1990 of $ 450 billion (Hopkins, 2002) and is likely to exceed $ 1 trillion by 2013. It is a fact that the preventive actions by theJapanese authorities after Fukushima have reduced radiological healthimpact substantially, as stable iodine was provided to evacuees, andthe government prohibited cultivation of all vegetables, and the useof local milk and other food products, whereas all children from theevacuation zone were measured for radioactivity by the end of March.
In contrast, millions of children ingested contaminated milk and foodproducts in ex-USSR after Chernobyl due to the lack of available information. Although the resulting deaths from Fukushima are smaller
than those of the earthquake itself (N20,000) and also than those from
Chernobyl, epidemiological studies should be conducted to re-assess
the estimates presented here.
Funding sources
This study was funded by the GIS Climat-Environnement-Société,(http://www.gisclimat.fr/projet/radioclimﬁre). It was also granted
access to the HPC resources of [CCRT/TGCC/CINES/IDRIS] under the
allocation 2012-t2012012201 made by GENCI (Grand Equipement
National de Calcul Intensif).
Conﬂict of interest statement
The authors declare that there are no conﬂicts of interest.
Acknowledgments
We appreciate Dr. Evaggelos Kritsikis (LSCE) and Dr. Olivier Evrard(LSCE) for the valuable discussions.
Appendix A. Supplementary data
Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/j.envint.2013.11.020.
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