Dose-Response Relationship: Health Effects In Residents at the High Background Radiation Areas of Ramsar, Iran SMJ Mortazavi, Ph.D Associate Professor.

Dose-Response Relationship: Health Effects In Residents at the High Background Radiation Areas

of Ramsar, Iran SMJ Mortazavi, Ph.D

Associate Professor of Medical PhysicsRafsanjan University of Medical Sciences,

Imam Ali Blvd., Rafsanjan, Iran.E-Mail: [email protected]

Mortazavi SMJ

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)UkrainePermanently Evacuated

• Nuclear accident fallout5.0 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

Cumulative dose (mSv)

MCAa in non -irradiated cells

MCAa in cells exposed to 1.5 Gy

HBRAb 7 2552 0.014 ± 0.004 0.106 ± 0.015 NBRA c 5 14.90 0.016 ± 0.002 0.188 ± 0.020 P-valued Not significant < 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.

Dose and k-Value

The 2nd-order polynomial model indicates an optimal induction of error-free DNA repair in a cumulative dose region of min k-value.

0

0.2

0.4

0.6

0.8

1

1.2

0 2000 4000 6000 8000 10000

Cumultive Dose (mSv)

k

Adaptive Response Region

Synergistic Effect Region Base Line

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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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