電子期刊 |
ISSN:1684-193X
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Updated
Oct 30, 2003
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Contents:
Volume 2, Supplement 1; October, 2003 |
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Sequelae of Chronic Radiation Exposure |
Hon-Ping Ma, MD; Chor-Ming Lin, MD; Tzong-Luen Wang,
MD, PhD |
From the Department of Emergency Medicine (Ma
HP, Lin CM, Wang TL), Shin-Kong Wu Ho-Su Memorial Hospital.
Correspondence to Dr. Tzong-Luen Wang, Department
of Emergency Medicine, Shin-Kong Wu Ho-Su Memorial Hospital, 95
Wen Chang Road, Taipei, Taiwan. E-mail M002183@ms.skh.org.tw
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Abstract
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Chronic radiation syndrome
is based upon victims who were exposed to radiation for at least
3 years and who had received at least 100 rem or more to the marrow. The report reconfirms the
International Commission on Radiological Protection (ICRP) recommendation
that the maximum value of the dose constraint to be used in the
optimization of radiological protection for a single source should
be less than l mSv in a year, and that a value of no more than about 0.3
mSv in a year would be appropriate.
Chronic exposure of radiation, who developed chronic radiation sickness,
leukopenia, thrombocytopenia and inhibition of non-specific
immunity factors, slight increase in nodule prevalence and thyroid
antibody-positive subjects, increased frequency of chromosomal aberrations
(both stable and unstable types) and CD3 – CD4+ mutant T-lymphocytes
in the peripheral blood. Studies show that radioactivity from nuclear
plants is getting into the environment and human body, and there
is now strong evidence that it is hurting the health of Americans.
There is now substantial evidence that exposure to radioactive releases
from nuclear reactors is a significant causal factor of increasing
childhood cancer rates and of other adverse health effects.
Key words--- Chronic Exposure; Radiation; Disaster |
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Introduction
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The
signs and symptoms of chronic radiation poisoning, or chronic
radiation syndrome, are based upon victims who were exposed to
radiation for at least 3 years and who had received at least 100
rem or more to the marrow.1
Chronic radiation syndrome is likely to be seen in people living
within the radioactive fallout zone and who are continuously exposed
to residual low dose radiation in their surroundings. Such victims
may complain of headaches, vertigo, sleep disturbances, chills,
epistaxis, poor appetite, generalized
weakness with rapid fatigue, bone pain, hot flashes, increased
excitability, loss of concentration,
impaired memory, mood changes, ataxia, paresthesias,
and syncopal episodes. Physical clinical
findings may include tachycardia, mild hypotension, localized
bone or muscle tenderness, intention tremor, ataxia, asthenia,
and hyperreflexia, or sometimes hyporeflexia.
Children who exposed in chronic radiation may be under developed
secondary sexual characteristics and delayed menarche. Lab findings
include mild to marked leukopenia, thrombocytopenia
and bone dysplasia. Gastric hypoacidity
and dystrophic changes may be present. If patient is removed from
the radiation environment, the clinical symptoms and findings
will be slowly resolve, and complete recovery has occurred from
the lower doses.
Members of the public persistently and adventitiously result in
prolonged exposures that are occasional to situations in which
they may find themselves. The average annual dose associated with
prolonged exposures is more or less constant or decreases slowly
over the years. Typical prolonged exposures are those delivered
by the so-called ‘natural’ sources such as cosmic radiation and
original radio nuclide decay chains. Some ‘artificial’ sources
may also deliver prolonged exposures; for example, long-lived
radioactive residues from human activities are a common cause
of prolonged exposure. It is to be noted that some radioactive
residues may contain both natural and artificial radio nuclides.
In situations of prolonged exposures, it may be difficult to separate
the exposure attributed to the artificial component from that
due to the natural component; likewise, protective measures against
the artificial component can affect the exposure due to the natural
component and vice versa.1
The report reconfirms the International Commission on Radiological
Protection (ICRP) recommendation that the maximum value of the
dose constraint to be used in the optimization of radiological
protection for a single source should be less than l mSv
in a year, and that a value of no more than about 0.3 mSv
in a year would be appropriate.2 It also stresses that
consideration should be given to exposure situations where combinations
of transient and prolonged exposures or a buildup over time of
prolonged exposures from a source could occur. In these situations
the report recommends verifying that appropriate dose assessment
methods are used for ensuring compliance with the established
dose constraint. The assessment should take account of any reasonably
thinkable combination and buildup of exposures. In a special situation,
such verification of compliance is not practical,
the report considers it judicious to restrict the prolonged component
of the individual dose from the source with a dose constraint
of the order of 0.1 mSv in any given
year during the operational lifetime of the source. Dose Limits:
In relation to dose limits, the report also reconfirms the ICRP
recommendation that the sum of the prolonged and transitory exposures
from all regulated practices should be restricted to a dose limit
of 1 mSv in a year. It also emphasizes
that the national authorities concerned and, as appropriate, relevant
international organizations should consider situations where there
could be a buildup of the prolonged components of the exposures
attributable to all regulated practices as a result of the accumulation
of radioactive residues from continuing practices. The aim should
be to prevent that the aggregated individual additional annual
doses attributable to all current practices and to predictable
future practices exceed the dose limit of 1 mSv
in a year.
The recommendations in the ICRP report are based on objective
assessments of the health risks associated with prolonged exposure
levels and on radiological protection attributes of various exposure
situations.2 However, the radiation
risks attributable to artificial sources of prolonged exposure
in relation to those due to natural sources, the members of the
public may have personal and difference views on this. This depending
on the origin of the exposure,
and usually results in differently perceived needs
for response and a different scale of protection. The reqiure
for protection is generally stronger when the source of exposure
is a technological by-product rather than when it is considered
to be of natural origin. Society usually ignored that typically elevated
prolonged exposures due to natural radiation sources, while relatively
minor prolonged exposures to artificial long-lived radioactive
residues are a cause of concern and sometimes prompt unnecessary
actions. This actuality of social and political attributes, usually
unrelated to radiological protection, mainly influences the final
decision on the level of protection against prolonged exposure.
Therefore, the ICRP report cautiously recognizes that it should
be seen as a provider of decision-aiding recommendations usually
based on scientific considerations on radiological protection,
the outcome of its advice will be expected to serve as an input
to a final decision-making process which may include other societal
concerns and considerations. The decision-making process for the
radiological protection of the public in situations of prolonged
exposure may include the participation of relevant stakeholders
rather than radiological protection specialists alone.
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The Role of Strontium-90 |
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In 1957 an explosion occurred at the depot
of radioactive waste in the Southern Urals. An area of 23,000 km2 was
contaminated, with contamination density of over 1 Ci/m2
for Strontium-90. The zone was named the East-Urals Radiation Trace
(EURT). The population about 270,000 persons distribute in total
217 populated areas. The residents of 22 villages with contamination
density of over 4 Ci/km2 for Strontium-90 were evacuated.
The times of evacuation differed from 7 to 670 days since the accident, depending
on the level of contamination.
In 1988-1993 an individualized registry was created at the Urals Research Center for Radiation Medicine (URCRM), which
included information on the residents of 22 evacuated villages and
a proportion of unevacuated residents
of the EURT area. Currently, the registry contains data on 30,000
residents. Of that number approximately 17,000 persons were born
before, and 12,000 after the accident, it including about 9,000
offspring of exposed residents evacuated from the EURT, and about
3,000 persons who were born after the accident and have been living
permanently in the EURT area.
According to the data first published by Romanov8 the
residents have received, over the 35-year period since the accident,
mean effective doses ranging from 23 to 530 mSv. The mean effective doses received by permanent residents
range from 5 to 60 mSv.
The first initiatory analysis of late radiation effects among the
population exposed in the Southern Urals in 1957 was guided in 1989-1991 based
on data from the individualized population registry. In accordance
with the results obtained, no statistically significant increase
in cancer mortality was registered in those dose groups, neither
did the study trace any increase in congenital malformations and
the proportion of childless marriages.3-5 Those
groups with mean effective doses for groups 1-4 being 40, 58, 120,
496 mSv . The analysis used mean-for-village doses calculated
based on levels of contamination densities for Strontium-90 suggested
by Romanov.6 Rural
residents of the Chelyabinsk oblast included a control group. It is
because of high suspicion of the results attributable to a wide
variety of mortality values for certain years and different age
groups, and the interpretation of the study results as hormesis
by some authors,7
there was a pressing need to continue collection of additional information
and perform a repeat analysis of data at a next stage of the study.
Over the period that had run out since the first publications the
data underwent the following changes: doses received by the population
were revised by G.N. Romanov8
due to which accumulated dose estimates increased up to 950 mSv
for some of the exposed people; more suitable control groups were
sampled which allowed to take into account the ethnic identity;
the information in the data base was updated and enhanced.
Mayak is the first nuclear weapons plutonium
production enterprise built in Russia and includes nuclear reactors, a radiochemical
plant for plutonium separation, and a plutonium production plant.
Shilnikova’s study is based on a registry
containing medical and dosimetric data
of the employees who began working at different plants of the Mayak
nuclear complex who developed chronic radiation sickness.9 Workers whose employment began between
1948 and 1958 exhibited a 6-28% incidence of chronic radiation sickness
at the different facilities. There were no cases of chronic radiation
sickness among those who began working after 1958. Data on doses
of external whole-body gamma-irradiation and mortality in workers
with chronic radiation sickness are presented.
A result of clinical observations and laboratory investigations
performed for individuals exposed to chronic radiation due to discharges
of about 3 million Ci of radioactive waste
from the Mayak Industrial Association
into the river Techa in 1949–1956 by Akleyev.10 The population of the villages was exposed
to a combined external gamma
radiation and internal radiation, mainly due to Strontium-90.
Under the nature of the exposure, critical organ for the exposed
residents is there red bone marrow. During the first 2–4 years after
the onset of chronic exposure, the peripheral blood were manifested
changes by leukopenia, neutropenia,
thrombocytopenia and inhibition of non-specific immunity factors,
at equivalent dose rates to red bone marrow of 300–500 mSv
per year, and higher. In the 1950s 940 residents with highest exposure
doses were diagnosed with chronic radiation sickness. The status
of hemopoiesis and immunity is normal
among most of the exposed subjects after the beginning of exposure
about 43–48 years later. However, the peripheral blood
of the exposed persons are still show an increased frequency
of chromosomal aberrations and CD3 – CD4+ mutant T-lymphocytes.
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The Problem concerning Strontium-90 and Human Health
in Taiwan |
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In Taiwan, chronic radiation has been
proved to be an effective immunity from cancers in an unusual “experiment”
carried out by; 10000 inhabitants who lived in about 1700 houses
unknowingly contaminated with 60Co for 10 to 15 yr. These houses
were constructed from 1982 through 1984 and found contaminated since
July 1992.11 Based on the experience of the contaminated
houses, the following conclusions can be deduced: 1. All
chronic radiation received in nuclear power plants and all peaceful
uses of nuclear energy may also be beneficial to human beings. All
the radiation protection policies, standards, and measures based
on International Commission on Radiological Protection theory and
recommendations should be properly modified. In addition, nuclear
workers and the general public should be told to stop worrying about
the risks of low-level radiation. 2. Chronic radiation from proper
doses from proper sources should be considered to be an effective
source of immunity from cancers. New knowledge about radiation effects
might be this: Acute, high-dose radiation from nuclear explosions
or accidents is harmful and the higher the dose, the higher the
harmful effects; however, it has a threshold value of ~200 to 500
mSv and might be beneficial with doses below that threshold.
Chronic radiation from nuclear power plants and other peaceful uses
might be a constant benefit to human beings. Luckey’s
investigations of many cases with lower doses, at ~5 cSv,
showed that cancer mortality was reduced to ~59.5%.12
A threshold value for chronic radiation may be determined from
the population with high doses in the Techa River area in Russia. It could be ten times higher
than for acute radiation. It would be very unlikely for human beings
to ever again receive such high doses. |
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Other Related Investigations |
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During 2001 and 2002, the Radiation and
Public Health Project, Inc. (RPHP) carried out a South Florida baby
teeth study and an initial study of radiation levels in the teeth
of children without cancer ("healthy teeth") and of children
diagnosed with cancer ("cancer teeth").13 The major findings of this study are: 1.
From 1986-89 to 1994-97, there was a 37% rise in the average levels
of radioactive Strontium-90 in southeast Florida baby teeth. This
rise reverses a long-term downward trend in Strontium-90 levels
that has occurred since the mid-1960s, beginning after the atmospheric
testing of nuclear weapons was banned. 2. This temporal trend of
increasing levels of radioactive Strontium-90 was found in 485 Florida teeth tested, 95% of which came from
six southeast Florida counties (Miami-Dade, Broward, Palm Beach, Martin, St. Lucie and Indian River). 3. When compared with baby teeth collected
from other Florida counties, the highest levels of Strontium-90
were found in the counties closest to the Turkey Point and St. Lucie
nuclear power plants. 4. The average levels of Strontium-90 found
in the 17 cancer teeth were 85% higher than the radiation levels
found in the 311 non-cancer teeth collected from children born in
the same years and in the same counties. 5. Recent measurements
of high energy beta activity, characteristic of Strontium-90 in
southeast Florida water samples, indicate that the highest levels occur within 20 miles of
the Turkey Point and St. Lucie nuclear power plants, ruling out
the fallout from past nuclear tests as the principal source of radiation
in Florida drinking water and baby teeth. The major
conclusions of this study are: 1. Radiation emissions from nuclear
power plants are the predominant cause of rising Strontium-90 levels
in southeast Florida baby teeth. 2. Radiation levels are significantly
higher in the teeth of children with cancer than in the teeth of
children without cancer. 3. There is now substantial evidence that
exposure to radioactive releases from nuclear reactors is a significant
causal factor of increasing childhood cancer rates and of other
adverse health effects in southeast Florida.
A study to determine the thyroidal consequences of the Chernobyl
nuclear power station accident in a selected Turkish population.14
This study was designed as a sectional, area study, between October
2000 and March 2001, in two different regions of Turkey. Although
there was a slight increase in nodule prevalence and thyroid antibody-positive
subjects in the study group, it is hard to conclude that Turkey was affected by the Chernobyl accident. These results, at least the
significant differences with regard to the prevalence of goiters
between groups, may reflect the different iodine status of the selected
regions.
Strontium-90 is considered to be one of the most hazardous bone-seeking
elements created in the fission of uranium or plutonium, because
of its long half life of 28 years and because it resembles calcium
so closely. By masquerading as calcium needed to form bone and teeth,
it is readily taken up and concentrates in bone. In a pregnant woman,
the Strontium-90 that has accumulated in the bone, together with
that in her diet, is transported with calcium into the rapidly dividing
cells of the embryo and fetus, where it can either kill or mutate
them by the emission of high-energy electrons or beta particles.
When Strontium-90 lodges near the bone marrow, where stem-cells
form blood and immune system cells, there is an increased risk of
leukemia, many other forms of cancer and autoimmune diseases, especially
in newborn infants and elderly adults whose immune system functions
are weak.
In early developmental stages of both humans, fish and other wildlife,
when cells rapidly reproduce, damage to the genes is not efficiently
repaired, so that if the cell survives and divides a defect is multiplied.
Thus cellular damage can lead to a greater risk of leukemia or cancer
in the newborn than in the mother, typically by anywhere from ten
to a hundred times as great, depending on the stage of development.
Moreover, many studies have shown that there is also an increased
risk of premature birth, low birth weight and birth defects. The
damage, which often does not become apparent until many years later,
is known to involve the developing immune, hormonal and central
nervous systems. In recent years, it has also been found that such
conditions as obesity, diabetes, high blood pressure, heart disease
and stroke can be the delayed result of the damage during development
in the womb, leading to a higher death rate, particularly for individuals
of abnormally low or abnormally high birth weight.
Especially serious is damage to different parts of the developing
brain such as the prefrontal cortex, which can result in dyslexia,
autism, and reduced cognitive ability. The reason is that neurons
communicate by sending out calcium ions, so that Strontium-90 and
Strontium-89 can be substituted for calcium, with devastating results
due to the enormous energy with which electrons or beta rays are
ejected from the nucleus in the course of the radioactive transformation
from Strontium-90 to Yttrium-90, destroying neurons in the process.
Part of the reason why Strontium-90 is so damaging is that radioactive
Yttrium-90, which has different chemical properties than Strontium-90,
concentrates in the hormone producing soft-tissue glandular organs
such as the pituitary gland, the pancreas, the thyroid, the male
and female reproductive organs, and the female breasts. Thus, key
hormones such as estrogen and testosterone can be affected both
during early development and later in life, when they play a major
role in breast and prostate cancer, as well as in reduced fertility,
premature births, sexual development and sexual orientation.
Another reason is that protracted exposures over periods of days,
months or years were discovered to be much more damaging biologically
than the same dose received in short diagnostic medical exposures
or flashes from a nuclear bomb explosion by factors of hundreds
to thousands of times. This is due to the greater efficiency of
free-radical oxygen molecules in puncturing cell-membranes, when
they are produced one-by one and do not become deactivated by colliding
with each other in the dense cluster produced during short X-ray
or gamma ray exposures. Thus, chronic exposures to Strontium-90
can produce cancer, immune system and respiratory damage such as
asthma at very low doses. Moreover, it has been found in laboratory
studies that Yttrium-90 also concentrates in the lung, so that the
ingestion of Strontium-90 can cause lung cancer.
In addition to the Strontium-90 dose to the human body or organ,
Strontium-90 is also an indicator of, or marker for, other radiation
doses received from the many shorter-lived fission products that
are produced together with Strontium-90 and released from nuclear
reactors both in liquid and airborne effluents that do not rise
high into the atmosphere. Elements such as Iodine-131, with an 8
day half-life and others with even shorter half-lives, can produce
many times the radiation dose of Strontium-90, just as occurred
during the early period of A-bomb testing in Nevada when the fallout came down in a matter
of hours.
Minimizing adverse health effects of emissions from nuclear power
reactors is an important element in any effective strategy to prevent
disease and death. Studies show that radioactivity from nuclear
plants is getting into the environment and human body, and there
is now strong evidence that it is hurting the health of Americans,
especially the health of the children on which the future of our
nation depends.
Because of the need to minimize risk and prevent disease, Radiation
and Public Health Project (RPHP) has initiated a national study
of Strontium-90 in baby teeth, with the goal of collecting and testing
several thousand teeth and correlating radioactivity levels found
in these teeth with cancer risk. A study of in-body radioactivity
levels in persons living near nuclear reactors is the most effective
means of studying whether radioactivity emitted from nuclear reactors
is affecting cancer levels in the U.S. To date, there have been no such studies
by the U.S. government, state health departments,
nuclear utilities, or other private researchers of the relationship
between in-body levels of radiation and public health around nuclear
reactors.
After reviewing the initial findings of the Baby Teeth Study in
1999, Dr. Sidel, past president of the American Public Health Association,
and Dr. Geiger, past president of Physicians for Social Responsibility,
stated: "If the levels of Strontium-90 in children's teeth
and the variations in levels by geographic area reported in this
study are validated by appropriate repetition, these findings would
appear to justify intensive follow-up and continuing large-scale
surveillance. Given the biological risk associated with body burdens
of even small amounts of long-lived radioactive Strontium-90, it
would be prudent to regard these findings as suggestive of a potential
threat to human health."
Southeast Florida typifies the recent rise of Strontium-90
levels in the nation, and has above average rates of childhood cancer,
especially within thirty miles of its nuclear plants. There is now
significant evidence that children diagnosed with cancer have higher
Strontium-90 levels in their bodies than children without cancer.
This is consistent with the discovery by Dr. Alice Stewart that
very low doses from a few diagnostic X-rays of the mother during
pregnancy lead to an excess risk of childhood leukemia and cancer.
It therefore appears that the combined data patterns of the highest
beta activity in water samples near the Turkey Point and St. Lucie
nuclear plants, of rising Strontium-90 in the deciduous teeth, and
of increasing cancer incidence make an extremely strong case that
the rising Strontium-90 found in the teeth of children born in the
late 1980s and early 1990s cannot be due to the atmospheric tests
that ended in 1980, or the venting of all underground bomb tests
that ended in 1993.
Furthermore, it appears that recent rises in the childhood cancer
incidence in Florida and the rest of the U.S. are causally related to internal exposures
to radioactive fission products. The adverse health effects related
to cancer and all diseases related to the human immune system and
hormonal system have been underestimated by factors of hundreds
to thousands of times, as recently concluded by the European Committee
on Radiation Risk.15
Since the levels of Strontium-90 in the teeth have kept rising throughout
the 1990s from their lowest values in the early 1980s long after
the end of all atmospheric tests in 1980 and more than five years
after the arrival of the Chernobyl fallout in 1986, it is no longer
possible to regard Chernobyl or atmospheric bomb tests as significant
sources of Strontium-90. Even the known venting from underground
nuclear bomb testing in Nevada ended in 1992, and in China by 1993,
making it impossible to regard the very high levels of Strontium-90
in both teeth with cancer and without cancer, found for children
born in the late 1990s, as due to underground tests.
Taken together with the fact discussed in the present report that
the highest levels of Strontium-90 beta activity in drinking water
were found nearest to the location of the two nuclear plants in
southeast Florida, there can no longer be any reasonable doubt that nuclear reactors are now
the major source of fission products in the environment.
Thus, it appears that a significant cause, or contributing cause,
of the two decade long rise in childhood cancer (including leukemia,
brain cancer, and other cancers) since the early 1980s are the bone-seeking
nuclear fission products such as Strontium-90, which are presently
only released into the environment by commercial nuclear reactors
in the United States, both in the course of accidents and during
routine operations within presently permitted limits.
The finding that children diagnosed with cancer have higher Strontium-90
concentrations in their teeth at birth than children without cancer
points to environmental radiation from nuclear reactors as the principal
cause of the mysterious cluster of brain and other cancers diagnosed
among infants and children in St. Lucie County. This cancer cluster
was documented by the Florida Department of Health (FDOH) in 1997
and subsequently studied by both state and federal health researchers,
who eliminated chemical carcinogens as a possible cause of the increasing
incidence of childhood cancers in St. Lucie County. During 1997-1999,
the Department of Health conducted a comprehensive study of 561
chemicals known or suspected carcinogens and concluded that "based
on comparisons to state and federal standards and toxicological
publications, none of these chemicals represents a health threat
or is associated with neuroblastoma or other childhood cancers."
But the FDOH study did not include a study of nuclear fission products
in environmental samples or in the deciduous teeth of children,
such as Strontium-90, that are chemically similar to calcium and
seek out bone, irradiating the bone marrow where the red cells of
the blood and the white cells of the immune system originate. Particularly
serious is the damage to the immune and hormonal system as well
as to the developing brain in the sensitive embryo, fetus and infant,
often acting synergistically with other environmental toxins as
Rachel Carson warned forty years ago in Silent Spring (1962). |
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