Childhood thyroid cancer since accident at Chernobyl
BMJ 1995; 310 doi: https://doi.org/10.1136/bmj.310.6982.801 (Published 25 March 1995) Cite this as: BMJ 1995;310:801All rapid responses
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The "Yablokov Report" on the radioactive waste disposal in seas
adjacent to Russian territory [1] is well known. It extracts material from
a report by a Commission appointed for this purpose by The Russian
President. This article has no clear-cut conclusions, the most significant
figure being 325 kCi, which is the estimate of the total activity of all
radioactive wastes dumped. A possible upper limit of this value was
estimated to be as high as 2.5 MCi [1] (only the latter figure is in the
summary available online). The following figures should be considered for
comparison. About 140 MCi of the main radionuclides were released due to
the Chernobyl accident [2]. In particular, for cesium-137 the Chernobyl
release was about 200 times higher than that from explosions both in
Hiroshima and Nagasaki combined [3]. In residents of contaminated areas
around Chernobyl, annual average effective doses were approximately 40 mSv
in the first year after the accident but decreased to less than 10 mSv in
the following years [3]. Doses to the evacuees were around 33 mSv [4].
These figures are below the limits of effective dose for workers [3]. The
vast majority of people residing in contaminated areas currently receive
an insignificant addition (less than 1 mSv) to the annual effective doses
from the natural background [4]. There has been no clearly demonstrated
increase in the incidence of cancers or other major public health impact
due to radiation from Chernobyl accident, except for the increase of
thyroid carcinoma among those exposed at a young age [2,4]. However, non-
radiation-related factors obviously played a foremost role in the post-
Chernobyl increase of paediatric thyroid cancer [5].
Atmospheric nuclear tests (1945-1980) were another major source of
radiocontamination. In the UNSCEAR 1993 Report [6], the most significant
radionuclides produced and globally dispersed in the atmosphere as a
result of the nuclear testing are listed together with corresponding
activity estimates, a calculated total activity being 68 MCi. The tests
have not added significantly to the global inventory of long-lived
radioactive material in the biosphere [7]. The world average annual dose
from atmospheric nuclear testing at its maximum in 1963 was 0.11 mSv,
having declined to less than 0.006 mSv in the 1990s [8]. A somewhat higher
deposition over the oceans did not affect the estimates of doses to humans
[9]. In a sense, atmospheric nuclear tests performed during the 1950s and
1960s can be regarded as an experimental imitation of a nuclear war. Note
that a nuclear war would result today (at a given yield) in a lesser world
-wide radiocontamination than the bygone atmospheric tests because of
predominance in modern devices of the nuclear fusion producing less
radionuclides than the fission. In the former Soviet Union, a major
nuclear testing site was in the Middle Asia (Semipalatinsk area). By the
end of the 20th century, no significant radioactivity increase in
consequence of the testing was found [10]. Annual effective doses from
residual contamination to inhabitants living outside the test site
boundaries were in the 1990s around 0.1 mSv [8]. Another testing site was
on the Novaya Zemlya archipelago in the Arctic Ocean. In 1962, after the
largest series of nuclear tests, additional dose to the inhabitants of the
northern regions of Russia was around 0.7 mSv/year; by the end of the 20th
century this value decreased to 0.02 mSv/year [10], which is negligible.
It is difficult to determine the minimal dose, reliably associated
with an elevation of cancer risk for humans; it was estimated to be around
200 mSv [11]. In fact, the "practical thresholds" [12] in humans are
probably higher than 200 mSv because of the biases inherent for
epidemiological research on stochastic effects of low doses. In small
animals, which must be more radiosensitive, the minimal doses reliably
associated with tumorigenesis are generally higher than those determined
in humans by epidemiological studies, being in the range of thousands or
several hundreds of mSv or mGy [13,14]. According to UNSCEAR, chronic dose
rates below 100 mkGy/h (876 mGy/year) would be unlikely to have any
significant effects on most terrestrial animal populations [15].
Undoubtedly, disposal of radioactive waste must be performed with
scientifically based precautions to prevent accidental local
contaminations. At the same time, the above figures demonstrate that the
waste deposition in seas adjacent to Russian territory could not have
caused any large-scale environmental impact. Accordingly, investigations
performed during 1992-94 did not detect any significant consequences of
radioactive waste disposal in the northern seas [10]. A concluding point
is that the Yablokov Report [1] can contribute to unfounded radiophobia.
1. Yablokov AV. Radioactive waste disposal in seas adjacent to the
territory of the Russian Federation. Mar Pollut Bull. 2001;43(1-6):8-18.
2. UNSCEAR 2000. Sources and Effects of Ionizing Radiation. Report to
the General Assembly. Annex J: Exposures and effects of the Chernobyl
accident.
3. Mould RF. Chernobyl record. The definite history of the Chernobyl
catastrophe. Philadelphia: Institute of Physics, 2000.
4. Environmental consequences of the Chernobyl accident and their
remediation: twenty years of experience. Report of the Chernobyl Forum
expert group 'Environment'. Vienna: IAEA, 2006.
5. Jargin SV. Thyroid cancer after Chernobyl: obfuscated truth. Dose
Response 2011; DOI: 10.2203/dose-response.11-001.Jargin
6. UNSCEAR 1993 Report. Sources and effects of ionizing radiation.
Annex B. Exposures from man-made sources of radiation.
7. UNSCEAR 1969 Report on the effects of atomic radiation. Annex A.
Radioactive contamination of the environment by nuclear tests.
8. UNSCEAR 2000 Report. Vol. I. Sources and effects of ionizing
radiation. Annex C. Exposures from man-made sources of radiation.
9. UNSCEAR 1966 Report on the effects of atomic radiation. Annex B.
Environmental contamination.
10. Mikhailov VN (Editor). Nuclear tests. Book 1. Nuclear tests in
the Arctic. Vol. 2. The Arctic nuclear testing site. Moscow: Moskovskie
Uchebniki, 2006. (in Russian)
11. Gonzalez AJ. Radiation safety standards and their application:
international policies and current issues. Health Phys 2004;87(3):258- 72.
12. UNSCEAR 1972 Report. Ionizing radiation: levels and effects.
Annex G: Experimental induction of neoplasms by radiation; Annex H:
Radiation carcinogenesis in man.
13. UNSCEAR 1986 Report. Genetic and somatic effects of ionizing
radiation. Annex B. Dose-response relationships for radiation-induced
cancer.
14. Moskalev IuI. Biological effects of low radiation doses. Moscow:
Institute of Biophysics, 1983. (in Russian)
15. UNSCEAR 2008 Report. Sources and effects of ionizing radiation.
Annex E. Effects of ionizing radiation on non-human biota.
Competing interests: No competing interests
Unrealistic laws and regulations are often violated, which
contributes to disrespect for law in general. Today's radiation safety
regulations are based on an LNT (linear no-threshold theory) principle
i.e. extrapolation of the dose-response relationships down to the minimal
doses, where such relationships are unproven and can be inverse due to
hormesis[1,2]. According to the existing standards, an equivalent
effective dose to individual members of the public should not exceed 1
mSv/year. The limits of effective dose for exposed workers are 100 mSv in
a consecutive five-year period, with a maximum effective dose of 50 mSv in
any single year. These figures should be seen in comparison with annual
exposures from natural background radiation: 1-10 mSv, with 2.4 mSv being
the global average [3]. In some densely populated regions the background
radiation is considerably elevated without any known increase of health
risks [4-6].
It is recognized that radiation-induced cancer is the most important
stochastic effect of ionizing radiation [7]. The non-stochastic
complications develop generally after higher doses [8]. In different
countries, there was some classified research on biological effects of
radiation. Publications that are open to the public, including the UNSCEAR
Reports, are partly tangled and non-transparent. There has been also
poorly substantiated information published in scientific journals [9],
further complicating the matter. It is hardly feasible for a reviewer to
determine the minimal dose level, reliably associated with an elevation of
cancer risk for humans; it appears to be around 200 mSv or higher (the
same figure is in [10]). There were also reports on carcinogenicity of
lower doses, but their validity is questionable [11]. In fact, the
"practical thresholds" [12] in humans are probably higher than 200 mSv
because of the biases typical for epidemiological research on stochastic
effects of low doses [13,14]. In small animals, which must be more
radiosensitive than humans, the minimal doses more or less reliably
associated with tumorigenesis often are higher than those determined in
humans by epidemiological studies, being in the range of thousands or,
less surely, hundreds of mSv or mGy [7,11,15]. There must have been also a
publication bias i.e. positive results being more frequently published and
better known than negative ones.
The LNT provides theoretical basis for the radiation safety
standards. It is supported by the following arguments: effects of ionizing
radiation are of a stochastic nature; the more high-energy particles or
photons hit a cell nucleus, the more DNA damage will result and the higher
the risk of malignant transformations will be. This concept does not take
into account that DNA damage and repair are permanent processes, normally
being in dynamic equilibrium. Living organisms will be probably best
adapted by selection to the natural background radiation. This is the case
for other environmental factors such as light and ultraviolet radiation,
temperature, atmospheric pressure etc., where deviation in any direction
from the optimum is harmful [16]. Further examples of hormesis are the
effects of vitamins, trace elements, and hormones, when a small amount of
the substance is beneficial but a larger amount is harmful [1]. For
ionizing radiation this concept is confirmed by epidemiological and
experimental evidence in favor of hormesis [1]. The natural selection is a
slow process; accordingly, the today's adaptation must correspond to some
average level from the past. Natural background radiation has probably
been decreasing during last millions of years, due to the decay of
radionuclides on the surface and oxygen accumulation in the atmosphere,
resulting in formation of the ozone layer; declining volcanic activity
bringing less radionuclides to the surface, etc. It means that ancient
intracellular mechanisms such as DNA repair had developed under the
conditions of higher radiation, so that living organisms must be adapted
to a higher background radiation level than that existing today [16].
Discussing the "vested interests behind exclusion of hormesis from
the current risk assessment methodology", Zbigniew Jaworowski writes: " It
seems to me that the driving force was (and still is) the vested interests
of the radiation protection establishment and of the antinuclear power
lobby, both concerned that demonstration of the beneficial effects of
small radiation doses, and thus of the existence of a threshold for
harmful effects occurring near this dose region, will destroy their raison
d'etre." [2]. The saying 'raison d'etre' should be probably replaced by
'cui prodest': strangulation of nuclear energy production contributed for
higher prices for fossil fuel. A concluding point is that radiation safety
norms should be revised to become more realistic and practically relevant.
Increase of the limits must be accompanied by measures guaranteeing their
strict observance. We found in literature no serious contraindications to
e.g. fivefold elevation of the total equivalent effective doses to
individual members of the public (up to 5 mSv/year), which would
correspond approximately to one CT scan in 2 years. Considering
unavoidable global spread of nuclear energy production, elevation of
limits for professional exposures (e.g. doubling) should be suggested as
well, bearing in mind the main goal of radiation safety regulations:
protecting people from harmful effects of radiation.
1. Prekeges JL. Radiation hormesis, or, could all that radiation be
good for us? J Nucl Med Technol 2003;31:11-7.
2. Jaworowski Z. Radiation hormesis - a remedy for fear. Hum Exp
Toxicol. 2010;29(4):263-70.
3. UNSCEAR 2000 Report. Sources and effects of ionizing radiation.
Annex B: Exposures from natural radiation sources.
4. Balaram P, Mani KS. Low dose radiation - a curse or a boon? Natl
Med J India 1994;7(4):169-72.
5. Ghiassi-nejad M, et al. Very high background radiation areas of
Ramsar, Iran: preliminary biological studies. Health Phys 2002;82(1):87-
93.
6. UNSCEAR 1988 Report. Sources, effects and risks of Ionizing
radiation. Annex F: Radiation carcinogenesis in man.
7. UNSCEAR 1986 Report. Genetic and somatic effects of ionizing
radiation. Annex B. Dose-response relationships for radiation-induced
cancer.
8. UNSCEAR 1982 Report to the General Assembly. Ionizing radiation:
sources and biological effects. Annex J: Non-stochastic effects of
irradiation.
9. Jargin SV. Overestimation of Chernobyl consequences: poorly
substantiated information published. Radiat Environ Biophys.
2010;49(4):743-5
10. Gonzalez AJ. Radiation safety standards and their application:
international policies and current issues. Health Phys. 2004;87(3):258-
72.
11. UNSCEAR 2000. Vol. II. Sources and effects of Ionizing radiation.
Annex G: Biological effects at low radiation doses.
12. UNSCEAR 1972 Report. Ionizing radiation: levels and effects.
Annex G: Experimental induction of neoplasms by radiation; Annex H:
Radiation carcinogenesis in man.
13. UNSCEAR 2006 Report. Vol. I. Effects of ionizing radiation. Annex
A: Epidemiological studies of radiation and cancer.
14. Watanabe T, et al. Hiroshima survivors exposed to very low doses
of A-bomb primary radiation showed a high risk for cancers. Environ Health
Prev Med 2008;13:264-270
15. Moskalev IuI. Biological effects of low radiation doses. Moscow,
Institute of Biophysics, 1983. (in Russian)
16. Jargin SV. Overestimation of Chernobyl consequences: biophysical
aspects. Radiat Environ Biophys 2009;48(3):341-4.
Competing interests: No competing interests
In the letter [1] it was noticed that in the volume 1181 (year 2009)
of The Annals of the New York Academy of Sciences (NYAS), dedicated to the
Chernobyl accident [2], references to non-professional publications (mass
media, websites of unclear affiliation, etc.) were used to back up
scientific views. One of the articles in this volume was additionally
commented in [3]. The photographs on the page 132, showing "typical
examples of Chernobyl-induced congenital malformations" [2], are
apparently cut out and stuck on a false background. The images were
published with a reference to a newspaper dated 1991 (see caption), but
the children on 2 lower photographs seem to be older than 5 years.
Furthermore, the following statement was made without references: "The
calculations suggest that the Chernobyl catastrophe has already killed
several hundred thousand human beings in a population of several hundred
million that was unfortunate enough to live in territories affected by the
fallout. The number of Chernobyl victims will continue to grow over many
future generations." [4] Then follows a misquoting: "Twenty years after
the catastrophe, the official position of the Chernobyl Forum (2006) is
that about 9,000 related deaths have occurred and some 200,000 people have
illnesses caused by the catastrophe." There are no such statements in the
Chernobyl Forum publication referred to [5]. On the pages 15-16 it is
written: "The international expert group predicts that among the 600 000
persons receiving more significant exposures (liquidators working in 1986-
1987, evacuees, and residents of the most 'contaminated' areas), the
possible increase in cancer mortality due to this radiation exposure might
be up to a few per cent. This might eventually represent up to four
thousand fatal cancers in addition to the approximately 100 000 fatal
cancers to be expected due to all other causes in this population." [5]
This statement, being itself based on an LNT (linear no-threshold theory)
principle, validity of which for low doses is unproven [6], was misquoted
in [4]. Numerous statements that are questionable or contradictory to
generally accepted knowledge are made in the NYAS Report without
references, for example: "The biological efficiency of cytogenic effects
varies depending on whether the radiation is external or internal:
internal radiation causes greater damage, a fact also neglected." [2]
External radiation is generally considered to be more effective than
internal at a given dose, which is particularly the case for thyroid
cancer [7], the only neoplastic sequel of the Chernobyl accident regarded
to be proven [5,8]. Another example: "From year to year there has been an
increase in non-malignant diseases, which has raised the incidence of
overall morbidity in children in areas affected by the catastrophe, and
the percent of practically healthy children has continued to decrease."
[2] This statement only confirms the well-known facts that, on one hand,
health care has improved after the Chernobyl accident and, on the other
hand, overdiagnosis and probably also manipulations with statistics have
taken place. [9]
Political discourses are out of place in a scientific article, but
they cannot be avoided if other scientific papers have been politically
influenced. The NYAS report [2] gives us an opportunity to purify science
from political influences. It shows that Chernobyl consequences were
overestimated in the former Soviet Union but not only there. The motives
for Chernobyl overestimation in the former Soviet Union were discussed in
[9]. In the West, among the motives were anti-nuclear sentiments,
widespread among some adherents of the Green movement, as well as deep-
seated Russophobia, which has had reasons, understandable looking at the
map. The world is changing today; and reasons for Russophobia are
vanishing. For example, a "very conservative estimate of cancer fatalities
in Europe attributable to Chernobyl - 889,336 to 1,778,672," calculated on
the basis of an LNT principle, was reported in [10]. Figures 899,310-
1,786,657 ("Number of cancer deaths resulting from the radionuclides Cs-
134, Cs-137, and Sr-90 released from the Chernobyl reactor") are given in
[2] for the entire world with reference to [11]. There follows
unsubstantiated debate on "millions of children who developed heart
disease, diabetes and thyroid cancers or dysfunctions."[10] Running titles
like "Nuclear's endless nightmare" and corresponding illustrations
contribute to the effect on readers [10]. Note that doses comparable to
those received from the natural background radiation are most probably not
carcinogenic at all [12], so that LNT-based extrapolations of this kind
are misleading. It has never been scientifically demonstrated that slight
anthropogenic elevation of radiation background is associated with any
harm for humans.
Chernobyl accident has been exploited to strangle worldwide
development of atomic energy [6], but it was necessary so: nuclear energy
production should not have been permitted to spread to overpopulated
countries governed by unstable regimes, swarming with actual and potential
terrorists. There are no thinkable alternatives to nuclear energy:
unrenewable fossil fuel will become more and more expensive, contributing
to affluence in oil-producing countries and poverty elsewhere. Worldwide
introduction of nuclear power is a necessity, but it will be possible only
after a concentration of authority within a powerful international
executive. It will enable construction of nuclear power plants in
optimally suitable places, considering all socio-political, geographical,
geological and other conditions. In this way, accidents like in Japan
today, will be prevented.
References
1. Jargin SV. Overestimation of Chernobyl consequences: poorly
substantiated information published. Radiat Environ Biophys 2010;49: 743-
5.
2. Yablokov AV, Nesterenko VB, Nesterenko AB. Chernobyl. Consequences
of the catastrophe for people and the environment. Ann N Y Acad Sci 2009;
vol. 1181.
3. Jargin SV. Reduction of radiocesium load: supplementation of Cs
versus its depletion by enterosorbents. Swiss Med Wkly 2011;141: w13166
4. Nesterenko AB, Nesterenko VB, Yablokov AV. Chapter II.
Consequences of the Chernobyl Catastrophe for Public Health. Ann N Y Acad
Sci 2009;1181: 31-220.
5. Environmental consequences of the Chernobyl accident and their
remediation: twenty years of experience. Report of the Chernobyl Forum
expert group 'Environment'. Vienna: IAEA, 2006.
6. Jaworowski Z. Observations on the Chernobyl Disaster and LNT. Dose
Response 2010;8: 148-171.
7. UNSCEAR 1993. Sources and Effects of Ionizing Radiation. Report to
the General Assembly. Annex F: Influence of dose and dose rate on
stochastic effects of radiation,. New York, United Nations, 1993; 619-728.
8. UNSCEAR 2000. Sources and Effects of Ionizing Radiation. Report to
the General Assembly. Annex J: Exposures and effects of the Chernobyl
accident. New York, United Nations, 1993; 451-566.
9. Jargin SV. Thyroid cancer after Chernobyl: obfuscated truth. Dose
Response 2011; DOI: 10.2203/dose-response.11-001.Jargin URL: http://dose-
response.metapress.com/media/988t62jyyj7ytkepty47/contributions/j/8/u/4/j8u4196670879036.pdf
10. Bertell R. Behind the cover-up. Assessing conservatively the full
Chernobyl death toll. Pacific Ecologist; Winter 2006.
http://www.scribd.com/mobile/documents/50890761/download?commit=Download...
11. Bertell R. The death toll of the Chernobyl accident. In: Busby CC
and Yablokov AV. (Eds.), ECRR Chernobyl 20 Years On: Health Effects of the
Chernobyl Accident. ECRR Doc. 1. Aberystwyth, Green Audit Books, 2006; 245
-248. (cited after [2])
12. Jargin SV. Overestimation of Chernobyl consequences: biophysical
aspects. Radiat Environ Biophys 2009;48(3): 341-344.
Competing interests: No competing interests
After the Chernobyl accident, many publications appeared
overestimating its medical consequences. Previously, we criticized some of
them, among other things, because of an inadequate use of the term "long-term low-dose exposure to ionizing radiation" and combination of the
patients from radiocontaminated areas and from the capital city of Kiev
within one research group, thus creating a ground for debate about
radiation-induced malignancy in the large city [1-2]. Average annual
individual effective doses of radiation, received by inhabitants of Kiev
during the first year after the Chernobyl accident (external irradiation
about 3 mSv plus internal irradiation 1.1 mSv, decreasing in the following
years) [3], were comparable with the global average annual doses from the
natural radiation background (2.4 mSv) [4]. In residents of contaminated
areas around Chernobyl (living in the strictly controlled zones, which
surround the 30 km exclusion zone, from where initial evacuation took
place), annual average effective doses received by the inhabitants were
around 40 mSv in the first year after the accident but fell to less than
10 mSv in the following years [4]. These figures are comparable with upper
limits of doses received from a single examination by computed tomography
(1-40 mSv) [5]. For comparison, 3,414 Uranium miners with lung cancer, who
worked in Germany in the period 1946-90, underwent mean individual
cumulative exposure over 800 WLM, which is equivalent to more than 4,000
mSv. [6]
References
1. Jargin SV. Over-estimation of radiation-induced malignancy after
the Chernobyl accident. Virchows Arch 2007; 451: 105-106
2. Jargin SV. Re: Involvement of ubiquitination and sumoylation in
bladder lesions induced by persistent long-term low dose ionizing
radiation in humans. Re: DNA damage repair in bladder urothelium after the
Chernobyl accident in Ukraine. J Urol 2007; 177:794-795
3. Borovikova NM, Burlak GF, Berezhnaya TI, et al. Composition of
irradiation dose of the population of Kiev after the accident at the
Chernobyl atomic power-station. In: Results of assessment of medical
consequences of the accident at the Chernobyl atomic power-station.
Proceedings of the Scientific and Practical Conference. Kiev, 1991: pp. 33
-34 (in Russian)
4. Mould RF. The Chernobyl Record. The Definitive History of
Chernobyl Catastrophe. Bristol & Philadelphia: Institute of Physics,
2000.
5. Mettler FA Jr, Huda W, Yoshizumi TT, Mahesh M. Effective doses in
radiology and diagnostic nuclear medicine: a catalog. Radiology.
2008;248(1):254-63.
6. Taeger D, Fritsch A, Wiethege T, et al. Role of exposure to radon
and silicosis on the cell type of lung carcinoma in German uranium miners.
Cancer. 2006; 106: 881-9
Competing interests: No competing interests
The accident at Chernobyl took place in April 1986.
From published reports it is clear to this observer that a whitewash of
the handling of the aftermath by the Russian authorities occurred.
Having spent my early years in communist East Germany I witnessed
many times the editing of life events as they happened; if the "fallout"
was obvious to all blame was assigned to outside forces such as capitalist
governments unhappy with the allegedly tremendous achievments of the
Soviet Union under communism.
Russia has always had a culture of denying its own weaknesses and
shortcomings and little has changed today.
Overestimating the often devastating effects from Chernobyl due to
better equipment, higher expectations of health problems and perhaps the
listing of patients from outside the regions brought to Chernobyl....
Your Honour I object.
Chernobyl was an accident waiting to happen, the cleanup cost lives
and many were damaged permanently.
Tell them about inflated figures.
Competing interests:
None declared
Competing interests: No competing interests
Recently we reviewed several publications overestimating medical
consequences of Chernobyl accident (1-3) and discussed possible causes of
overestimation of thyroid carcinoma (TC) incidence increase after the
Chernobyl accident (4). The case-control study (5) is one of the main
pieces of evidence in support of the cause-and-effect relationship between
exposure to 131I in childhood and TC increase after the Chernobyl
accident. The study included 276 patients with TC from radiocontaminated
areas, who were aged younger than 15 years at the time of the accident,
and 1300 controls matched to the patients by age, sex and area of
residence at the time of the accident. Individual dose estimates in
patients and controls were “based on their whereabouts and dietary
habits.” These data were obtained by means of a questionnaire. A strong
dose-response relationship was observed between radiation dose to the
thyroid, received in childhood, and thyroid cancer (P<.001) (5). It
should be commented that questioning, performed years after the accident,
can provide only approximate information. Such data can be easily adjusted
to a preconceived idea. Manipulations with statistics were not uncommon in
the Soviet medical science (6). A data adjustment could have contributed
to the high level of statistical significance of the relationship between
the dose and cancer risk, declared also for relatively low doses. These
considerations are applicable also to other studies applying retrospective
dose estimation (7,8). As we have discussed previously (3,4), the reported
incidence increase of TC after the Chernobyl accident was partly caused by
improved diagnostics, screening, and high tumor expectancy, which, in the
circumstances of primitive laboratory equipment and shortage of modern
literature, inevitably went along with some percentage of false-positive
conclusions. Registration of borderline lesions (e.g. well-differentiated
tumors of uncertain malignant potential) as carcinomas could have
additionally contributed to the high incidence figures. Besides, it was
known by physicians and general public that in contaminated areas medical
examinations by means of modern equipment are performed. At a suspicion of
thyroid disease, some children from other regions were brought to the
contaminated areas for the purpose of medical examination or treatment
within the framework of international programs. Required data on
whereabouts during and after the accident could have been confabulated in
such cases. Therefore, reported incidence increase of thyroid carcinoma
after Chernobyl accident and, correspondingly, cause-and-effect
relationship between the exposure to 131I in childhood and TC, should be
regarded as overestimated.
References
1. Jargin SV. Over-estimation of radiation-induced malignancy after
the Chernobyl accident. Virchows Arch (2007) 451(1):105-106.
2. Jargin SV Re: Involvement of ubiquitination and sumoylation in
bladder lesions induced by persistent long-term low dose ionizing
radiation in humans. Re: DNA damage repair in bladder urothelium after the
Chernobyl accident in Ukraine. J Urol (2007) 177(2):794.
3. Jargin SV. Overestimation of medical consequences of increased
background radiation (in Russian). Meditsinskaia radiologiia i
radiatsionnaia bezopasnost' [Med Radiol and Radiation Safety] (Moscow)
(2008) 53(3):17-22.
4. Jargin SV. Overestimation of thyroid cancer incidence after
Chernobyl. Health Phys (2009) 96(2):186.
5. Cardis E, Kesminiene A, Ivanov V, et al. Risk of thyroid cancer
after exposure to 131I in childhood. J Natl Cancer Inst (2005) 97(10):724-
32.
6. Jargin SV. Manipulation with statistics in medical research.
Dermatopathol: Pract & Conc (2009) 15(1):21. Available at:
http://derm101.com
7. Tronko MD, Howe GR, Bogdanova TI, et al. A cohort study of thyroid
cancer and other thyroid diseases after the chornobyl accident: thyroid
cancer in Ukraine detected during first screening.
J Natl Cancer Inst (2006) 98(13):897-903.
8. Davis S, Stepanenko V, Rivkind N, et al. Risk of thyroid cancer in
the Bryansk Oblast of the Russian Federation after the Chernobyl Power
Station accident. Radiat Res (2004) 162(3):241-8
Competing interests:
None declared
Competing interests: No competing interests
Re: Childhood thyroid cancer since accident at Chernobyl
The following figures are presented in the text and the table of the article [1]: in Belarus (population about 10 million) during 1981-85 the absolute number of thyroid cancers (TC) in children under 15 yrs (in brackets: “rates expressed as annual averages per million children under 15” [1]) was 3(0.3); the same for Ukraine (population about 52 million): 25(0.5). For 5 northern regions of Ukraine (where the contamination after the Chernobyl accident subsequently occurred) the lowest TC incidence rate is given: 1(0.1). So it is written in [1]; but the values in brackets are inexact. According to the population pyramids for Belarus http://www.nationmaster.com/country/bo-belarus/Age-_distribution 1990 and Ukraine http://www.nationmaster.com/country/up-ukraine/Age-_distribution (both for 1990; accessed 30 June 2012), children under 15 yrs constitute a little more than 12 % of the entire population of both countries. Therefore, the approximate annual rate for Belarus would be: 3 cases in 5 years per 1.2 million children results in up to 0.5 for Belarus, and 25 cases/5 years x 6 million children = 0.83 for Ukraine. For the northern Ukrainian regions the incidence rate would be correspondingly 0.17 per 1 million. The above figures from [1] were reproduced in the Table 63 of the IARC publication [2] with reference to [1]; but the rates are designated “Rate/Million” which can be understood a rate for the whole period (1981-85) and for the whole population of the corresponding countries (e.g. 3 cases/10 million inhabitants of Belarus = 0.3 per 1 million); which, however, would be at variance with the original meaning in the quoted publication [1].
Comparable absolute figures for 1986 (the year of the Chernobyl accident) and subsequent years are given in the Tables 56 and 57 of the UNSCEAR 2000 Report [3], with references to 3 "Communications to the UNSCEAR Secretariat" and 1 Symposium proceeding: in 1986 in Belarus there were 3 paediatric TC cases and in Ukraine - 8 cases. The rates are given in the Table 57 per 100,000 children under 15 years at diagnosis: 0.2 both for Belarus and for Ukraine [3]. However, the calculations like in the first paragraph of this Rapid Response resulted in somewhat different incidence rates for the year 1986: 0.25 and 0.13 per 100,000 or 2.5 and 1.3 per 1 million children in Belarus and Ukraine correspondingly.
The figures from the first paragraph of this Rapid Response for the period immediately preceding the Chernobyl accident (1981-85) are relatively low in comparison to those for other developed countries. Thyroid cancer is the most frequent tumour of endocrine glands in children and adolescents; its incidence rate was estimated to be 2-5 per 1 million per year. [4]. The US Cancer Registry SEER (Surveillance Epidemiology and End Results) reports an annual age-adjusted incidence rate, based on cases diagnosed in 2000-2004, of 8.5 per 100,000, approximately 2.1% being diagnosed under the age 20 [4]; which corresponds to the annual incidence rate in the latter age group of around 1.8 per 1 million. Corresponding data from a regional Tumour Registry in Würzburg, Germany are given in [4], where age-adjusted incidence rate per 1 million for the age under 20 yrs was equal to 2.0 [4]. However, more enlightening are the figures from [5] available on-line as a table in [6]: http://www.scielo.br/img/revistas/abem/v51n5/a11tab1f.gif (accessed 30 June 2012). It is clearly visible from this table that incidence of paediatric TC is higher in more developed countries, obviously in consequence of better diagnostics. Comparing these figures with those for Belarus and Ukraine, given in the first paragraph of this Rapid Response, it is evident that there must have been a pool of undiagnosed TC in the former SU before the Chernobyl accident. In Russian Federation, TC was started to be registered as a separate entity only in 1989 [7], when the screening after the Chernobyl accident had been initiated and the registered TC incidence began to increase dramatically. In conclusion, the post-Chernobyl incidence increase of TC was largely caused by detection due to the mass screening (performed most vigorously among children) of old neglected cancers plus cases brought from non-contaminated areas and registered as Chernobyl victims and some overdiagnosis [8-10], rather than by radiogenic cancers. These facts should be taken into consideration for further development of the radiation safety norms [11].
References
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2. International Agency for Research on Cancer (IARC). Ionizing radiation, Part 2. Some internally deposited radionuclides In: IARC monographies on the evaluation of carcinogenic risks to humans IARC Press, Lyon, 2001; vol. 78, p. 234.
3. United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) 2000 Report to the General Assembly. Sources and effects of ionizing radiation. Annex J. Exposures and effects of the Chernobyl accident.
4. Luster M., Lassmann M., Freudenberg L.S., Reiners C. Thyroid cancer in childhood: management strategy, including dosimetry and long-term results. Hormones (Athens). 2007;6(4):269-78.
5. Parkin D.M., Kramárová E, Draper G.J., Masuyer E., Michaelis J., Neglia J., et al. (editors). International incidence of childhood cancer. IARC Scientific Publication No 144. Lyon: IARCPress, 1999.
6. Demidchik Y.E., Saenko V.A., Yamashita S. Childhood thyroid cancer in Belarus, Russia, and Ukraine after Chernobyl and at present. Arq Bras Endocrinol Metabol. 2007;51(5):748-62.
7. Parshkov E.M. Analysis of thyroid cancer morbidity. In: Lushnikov E.F. Tsyb F., Yamashita S. Thyroid cancer in Russia after Chernobyl (in Russian with English summary). Moscow: Meditsina, 2006; pp. 36-59.
8. Abrosimov A.Iu. Thyroid carcinoma in children and adolescents of Russian Federation after the Chernobyl accident. Thesis (in Russian), Obninsk, 2004.
9. Jargin S.V. Thyroid cancer after chernobyl: obfuscated truth. Dose Response. 2011;9(4):471-6.
10. Jargin S.V. On the RET Rearrangements in Chernobyl-Related Thyroid Cancer. J Thyroid Res. 2012;2012:373879.
11. Jargin S.V. Hormesis and radiation safety norms. Hum Exp Toxicol. 2012; doi: 10.1177/0960327111431705
Competing interests: No competing interests