Dose-Response Relationship:
Health Effects In Residents at the
High Background Radiation Areas
of Ramsar, Iran
SMJ Mortazavi, Ph.D
Associate Professor of Medical Physics
Rafsanjan University of Medical Sciences,
Imam Ali Blvd., Rafsanjan, Iran.
E-Mail: [email protected]
Radiation and Life
• Life evolved in a radiation
field that was much more
intense than today.
– Higher Concentration of
Radioactive Elements
– Natural Reactors
• Natural background
radiation levels on Earth
vary by at least two orders
of magnitude.
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Radioadaptation History
• It has been long known
that protozoa and
bacteria exposed to
artificially lowered
levels of natural
radiation demonstrate
deficiency symptoms
expressed as
dramatically decreased
proliferation.
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Natural Radioactivity and
Radioresistance
• Radioresistance in living creatures of high
background radiation area has long been a
matter of interest for scientists.
• More than thirty years ago, experiments on the
Drosophila nebulosa showed that the flies
collected in a high background radiation area in
Brazil were more radioresistant than those of an
adjacent area (Kratz 1974).
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• According to UNSCEAR 2000 report,
Ramsar, a city in northern Iran has some
inhabited areas with the highest known
natural radiation levels in the world.
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Why so Hot?
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Radium Carbonate
• When the groundwater
reaches the surface at hot
spring locations, travertine,
a calcium carbonate
mineral (CaCO3),
precipitates out of solution
with dissolved radium
substituting for calcium in
the mineral.
• Radium Carbonate
（RaCo3）
• Molecular Weight 286.03
• Color: White
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Radioactive Bedroom
• Two survey meters show
the dose rates of 142 and
143 μGy/h on the wall of
the bedroom of one
dwelling.
• The owner has used the
sedimentary stones formed
at hot springs for
construction of his house.
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Where Do We Need Regulations?
The ICRP-recommended annual effective dose limit for
radiation workers is 20 mSv. The annual effective dose
in HLNRAs of Ramsar is a few times higher than this
limit.
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Where Do We Need Regulations? (cont.)
• City of Pripyat,
(near Chernobyl)
Ukraine
Permanently Evacuated
• Nuclear accident fallout
5.0 mSv/year
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• Prof. Sohrabi yesterday stated that the
residents of Ramsar have been always
considered as laboratory mice.
• No Help for Relocation
• No Economic Assistance
• No Remedial Action
• No Long-term or Short-Term Plan!
• Just continuous sampling (blood, teeth!…)
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Expense of Remedial Actions
• Because of the expense
of remedial actions and
the long history of high
background radiation
levels, it is nearly
impossible to ask the
inhabitants to carry out
remedial actions.
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• Should the Residents be aware of the
extra high radiation levels in their
environment?
• Should the government financially help
them to do remedial actions (basements,
floors…) or even evacuate the HBRAs?
• Why these are not simple questions?
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Lesson Learned From Chernobyl
Accident:
•
•
•
•
•
Health effects caused by radiation
Health effects caused by fear of radiation
Psychological considerations
Economic considerations (land Cost)
Social considerations (relocation)
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Radon in Ramsar
• Radon levels up to 3700 Bq/m3 (over 100
pCi/L).
• The people and their ancestors exposed to
abnormally high radiation levels over many
generations.
• If a radiation dose of a few hundred mSv per
year is detrimental to health causing genetic
abnormalities or an increased risk of cancer, it
should be evident in these people.
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Radon Prone Houses
• It is often difficult to sell a radon
prone house in the US or in other
developed countries
• It is nearly impossible to ask the
inhabitants of high level natural
radiation areas HLNRAs of
Ramsar to carry out remedial
actions.
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Study Design
• Ramsar is divided into eight health districts
and a health center provides primary health
services in each health district.
• Indoor radon concentration levels were
previously measured in each dwelling by
the Iranian Nuclear Regulatory Authority
experts.
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Cancer Mortality
• The overall cancer mortality, lung
cancer mortality and neonatal death
rate of different districts in the years
from 2000 to 2001 were collected.
• The radon prone houses were located
in a district named Ramak.
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Surprising Results
• Our study showed that the highest lung
cancer mortality rate was in Galesh
Mahaleeh, where the radon levels are normal.
• On the other hand, the lowest lung cancer
mortality rate was in Ramak, where the
highest concentrations of radon in the
dwellings were found
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Crude Lung
Cancer Rate
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Adjusted Lung
Cancer Rate
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Adaptive Response
Study group Sample
size
b
HBRA
7
NBRAc
5
d
P-value
Cumulative
dose (mSv)
2552
14.90
MCAa in nonirradiated cells
0.014  0.004
0.016  0.002
Not significant
MCAa in cells
exposed to 1.5 Gy
0.106  0.015
0.188  0.020
< 0.001
Table 3: Frequency of chromosomal aberrations in non-irradiated and
irradiated cells of the residents of high background radiation areas
and the residents of the control area.
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Dose and k-Value
1.2
1
Synergistic Effect Region
Adaptive Response Region
0.8
k
Base Line
0.6
0.4
0.2
0
0
2000
4000
6000
8000
10000
Cumultive Dose (mSv)
The 2nd-order polynomial model indicates an optimal induction of
error-free DNA repair in a cumulative dose region of min k-value.
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HBRAs and the Radiation
Protection Policy
• Considering LNT and ALARA, residents’
health could be severely affected and public
health in HBRAs like Ramsar would be best
served by relocating the inhabitants.
• In spite of this, the residents’ health seems
unaffected and relocation is upsetting to the
residents (Mortazavi and Karam 2002)
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Other HBRAs’ Biological Findings
• Based on the findings obtained by studies on
the health effect of high levels of natural
radiation in other HBRAs:
No consistent detrimental effect has
been detected so far.
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Other HBRAs (cont.)
• The level of natural radiation in Kerala is
about 10 times higher than that of normal
background areas.
• The average life span of Kerala residents is
72 years, while for all India, it is only 54
years (Goraczko 2000).
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Should we replace the LNT with better
Models?
Dr.
Comby’s
ALAIN?
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Mortazavi et al., Advances in Space Research, Vol 31, No. 6, 1543-1552, 2003
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