The following is taken from “Low-dose ionizing radiation exposure: Understanding the risk for cellular transformation” By L. DE SAINT-GEORGES,*
SCK•CEN, Department of Radiobiology, Mol, Belgium. Published in: Journal of Biological Regulators and Homeostatic Agents
Received:May 15, 2004, Accepted:June 26, 2004. Full paper download link:http://www.radiationhormesis.com/RadiationHormesis/Low-dose%20ionizing%20radiation%20exposure.pdf
An important question is about a hypothetical dose threshold. Does a threshold dose, below which the risk is nil, exist? According to what has been previously said on, the essentially random interaction of radiation with various biological molecules, it appears to make sense to consider a decrease of the risk with a decrease of the dose. However, no data exist which allows us to define a threshold value.
However, at low dose not only harmful effects but also possibly beneficial effects of radiation could occur. Here it is essential but not always evident, to clearly differentiate possibly beneficial effects from the lack of noxious effects.
Adaptive response and hormesis are often mentioned to minimize the risk of radiation or sometimes to deny any adverse outcome below a dose threshold, as detailed below.
Hormesis is a hypothesis that emphasises the possible beneficial effect of low doses of radiation and claims the necessity of a low-dose exposition to get some benefits while excluding any risk. However, this concept is controversial.
According to the hormesis model, people should be exposed to low radiation dose unless it is demonstrated with certitude that there is no benefit from such exposure. The possibility of adverse effects is not even considered.
We may wonder why the proponents of the hormesis model acknowledge a radiation threshold value for harmful effects, but reject it for beneficial effects.
Considering the essentially random interaction between radiation and target molecules leading to unpredictable molecular damage, it appears surprising that at low doses only beneficial effects would occur while noxious effect would require a dose above a certain threshold. To consider hormesis as an argument against actual dose limits would only be valid if the efficacy of hormesis could be demonstrated for the effects against which one wants to protect at low radiation doses, i.e. cancer and genetic damages.
Unfortunately this is not yet demonstrated in an unequivocal way. Therefore, the hormesis model is currently not considered in radioprotection.
The theory of “adaptive response”, (not to be confused with hormesis) shows that a low dose can reduce the effect of a higher dose when administered after a short time delay. This theory is based on substantial evidence.
To reduce a risk appears beneficial, but it does not mean that the risk is eliminated. According to the “adaptive response” model, a first low dose (conditioning dose) is considered to stimulate the DNA repair mechanisms that contribute to reduce the effect of a subsequent higher dose. But the initial low dose can only stimulate the limited number of cells actually hit, the total of which in function with the dose. This situation never excludes the possibility of a transformation of one of the cells.
The next higher dose concerns all cells. Some of them having the repair mechanisms stimulated by the first conditioning dose, and may repair the damage more easily. The other cells, that were not previously hit, are not protected. The total damage can be reduced by a factor depending on the number of the cells conditioned but will always be dependent on the total number of the cells exposed to both doses.
Would the conditioning of all cells solve the question? No, because to reach such a goal we have to increase the conditioning dose and the risk remains proportional to the dose and to the number of cells irradiated.
Therefore the adaptive response does not appear to be a relevant mechanism for radiation protection because the (low) conditioning dose that defines it, also generates a risk of transformation. On the other hand the challenging dose is not a low dose.
We suggest that natural background irradiation and metabolic ROS are already stimulating toward some adaptive response by a constant stimulation of the repair mechanisms. Then it would appear that there is no need to add to this radiation burden.
Evolution, in our natural radioactive environment, is often used as an argument to support such beneficial effects of low-dose radiation. We should remember that if Evolution has led to the current scala of successfully living species, the eliminated species are unavailable to analyse the non-beneficial aspect of evolution.
Conclusion: Is a low dose radiation safe or not?
The possible different interactions between rays and target atoms, the different types of ROS and free radicals produced, the different molecules as end points of ROS and the heterogeneity of damage in the target molecules makes the effect of ionization essentially unpredictable. Therefore, it does not seem to be appropriate to predict either deleterious or beneficial effects. Any issue from primary radiation effects remains theoretically possible.
The probability of having an effect, whatever it is depends on the dose and the number of cells being hit. However, the biological consequences can vary greatly and a distinction must be made between the organism as a whole, and the fate of individual cells. Indeed the worst issue for the cell, the cell death, is probably the best issue for the organism which in this way remains protected from transformed cells.
Cellular transformation does not threaten the life of the (cell) as it results in unlimited proliferation, but it may lead to the death of the entire organism.
Even if the probability of a transformation is no more important than the probability of any other effect, we must consider that the final outcome for the organism will be more determined by cellular transformation than by any other effect on cells. For radiation protection the fate of the organism should prevail above the fate of individual cells.
The biological effects of ROS and free radicals (and hence of radiation) are ultimately determined by the effect on the biosystem that controls the enormous burden of oxidative damage that is essentially resulting from metabolic ROS.
Checking the radiosensitivity is checking the integrity and efficiency of the control biosystems, e.g. the DNA repair system, the immune system, cell cycle control, and apoptosis.
Due to space limitations, we have not considered all elements dealing with low-dose exposition. For example, Linear Energy Transfer, dose rate, bystander effect, genomic instability and questions related to internal radiation emitters, were not considered. Nevertheless, this review should contribute to the understanding of the relative risk linked to low-dose and low-dose rate radiation exposure
The Linear No Threshold hypothesis should remain so far the basic guide line for the radioprotection authorities. It appears clearly that the ALARA (As Low As Reasonably Achievable) principle, which is currently the basis of radiation protection policies, should be followed as long as no relevant scientific facts provide other insights. The very weak probability of oncogenic events at low dose should reassure everybody.
If any beneficial effects from low-dose radiation should exist, we can not exclude them, there is no reason to expect a higher occurrence probability for them than for cell transformation and the one would never exclude the other possibility in other cells. Therefore, such concepts aimed to attenuate the risk perception, will only lead toward more confusion, which in turn will generate more unwarranted anxiety and will finally be totally counterproductive.” end quote.
Reprint requests to:
Dr. Louis de Saint-Georges, SCK/CEN, Radiobiology Boeretang 200 B-2400 Mol, Belgium
L. DE SAINT-GEORGES :
Secretary treasurer of European Radiation Research Society – Senior scientist
“Addressing the South Australian Chamber of Mines and Energy in Adelaide, chair of the uranium company Toro Energy Erica Smith said the true cost of coal was not yet being paid for by the community. She also said that there was a strong argument that some radiation “was good for you” …..”
Adelaide Advertiser newspaper, August 13, 2011 page 7.
Smith, representing her employer, a uranium miner, states that a “strong argument” claims that “some radiation” was “good for you”.
How much uranium is required to produce this “good radiation” ? And how is that “good radiation” to delivered to the people of this state? Via the milkman? The radiation emitted by uranium and its decay products have to be present within the human body to have any effect. How would a purchaser of the product know that the radiation emitted was “good” or “bad”?
If Toro Energy are referring to medical experimentation in a research lab, how well is the uranium mining industry able to replicate the control over experiment conditions possessed by such a research lab? The experimenters can turn x ray machines on and off. Can uranium miners switch the radiation emitted by Uranium and its decay products released into the biosphere, on and off?
The substances liberated into the biosphere by uranium mining of Uranium 238.
The decay of Uranium 238 consists of the following isotopic steps:
1 Thorium 234
2 Uranium 234
3 Thorium 230
4 Radium 226
5 Radon 222 (a gas)
6 Polonium 218 (solid particulate)
7 Lead 214
8 Bismuth 214
9 Polonium 214
10 Lead 210
11 Bi 210
12 Polonium 210
13 Lead 206 (Stable, not radioactive).
(Source: “NCRP Report No. 77, Exposures from the Uranium Series with Emphasis on Radon and its Daughters” March 15, 1984, National Council on Radiation Protection and Measurements, 7910 Woodmont Ave,
Bethesda, MD 20814, USA.)
To examine Toro Energy’s proposal or “argument” that the “some radiation” is beneficial, “good for you”, I have to define the type and energy of the radiations emitted by each of the radioactive substances that exist in the uranium 238 decay chain. And then compare the specifications to the source of the “strong argument” for “good” radiation or beneficial radiation as proposed by Toro Energy.
The Uranium 238 Decay Chain Type of Radiation, Energy of Radiation
Uranium 238 Curies/gram: 3.3 × 10^-7 (10 to the power of -7) Energy of radiation in MeV 4.2 Alpha Half life 4.5 billion years.
(Source: U.S. Department of Energy Office of Environmental Management – Depleted Uranium Hexafluoride Management Program Characteristics of Uranium and Its Compounds, pdf at http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CEgQFjAC&url=http%3A%2F%2Fweb.ead.anl.gov%2Furanium%2Fpdf%2Furaniumcharacteristicsfs.pdf&ei=z2d3UdHYFMaaiQf08oHwCQ&usg=AFQjCNGceU4pKOcz8wckBEw0cFNgC44O8w&bvm=bv.45580626,d.aGc&cad=rja
1 Thorium 234 Beta energy 0.270 MeV Beta and Gamma (Source: TOXICOLOGICAL PROFILE FOR THORIUM, Agency for Toxic Substances and Disease RegistryU.S. Public Health Service http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=18&ved=0CFkQFjAHOAo&url=http%3A%2F%2Fwww.atsdr.cdc.gov%2Ftoxprofiles%2Ftp147.pdf&ei=bGt3UcfPH–yiQfylYGoCg&usg=AFQjCNFK8MfTlIU5ojEwoS0gXl9fPgwoYw&bvm=bv.45580626,d.aGc&cad=rja )
2 Uranium 234 curies/gram 6.2 × 10^-3 Energy of radiation 4.8 MeV Alpha Half Life 248,000 years. (Source: as for uranium 238)
3 Thorium 230 Beta energy 4.6 MeV Half life 7.54×10^4 years (Source: TOXICOLOGICAL PROFILE FOR THORIUM, Agency for Toxic Substances and Disease RegistryU.S. Public Health Service
4 Radium 226 Alpha energy 4.870 MeV, Half Life 1,600 years (Source:Agency for Toxic Substances & Disease Registry, Toxicological Profile for Radium, 3. Chemical and Physical Information http://www.atsdr.cdc.gov/toxprofiles/tp.asp?id=791&tid=154
5 Radon 222 (a gas) Alpha energies 4.826 MeV(0.0005%) 4.986 MeV(0.078%) 5.48948 MeV(99.920%) gamma energies 0.510 MeV(0.076%) (Source: TOXICOLOGICAL PROFILE FOR Radon, Agency for Toxic Substances and Disease Registry U.S. Public Health Service, http://www.atsdr.cdc.gov/toxprofiles/tp.asp?id=407&tid=71
6 Polonium 218 (solid particulate) Alpha energy 5.998MeV (Source: National Academy of
Sciences National Research Council NUCLEAR SCIENCE SERIES 3037 MASTER The Radiochemistry
of Polonium page 4. OSTI pdf link : http://www.osti.gov/bridge/purl.cover.jsp?purl=/4034029-SolPsF/
7 Lead 214 (Beta and Gamma emitter)Beta energy 0.29 MeV Gamma energy 0.25 MeV (Source: Radiation and Health – Page 74, Thormod Henriksen, David H. Maillie CRC Press, 05/09/2002)
8 Bismuth 214 (Beta and Gamma emitter) Beta Energy 0.65 MeV Gamma Energy 1.46 MeV (Source: as for Lead 214)
9 Polonium 214 Alpha energy 7.680 MeV (Source: as for Polonium 218)
10 Lead 210, Energies : Gamma: 13 keV (25%), 47 keV (4%)
Beta: 17 keV (80%), 63 keV (20%)
Electrons: 30 keV (58%), 43 keV (13%), 46 keV (4%)
Alpha: 3720 keV (<1%)
Half-Life [T½]: Physical T½:2 22.3 years
Biological T½:3 ~ 1.5 days
Effective T½: ~ 1.5 days
Specific Activity1: 76.8 Ci/g [2.84E12 Bq/g]
(Source: Nuclide Safety Data Sheet Lead – 210 http://www.nchps.org)
11 Bismuth 210 Alpha energies: 4.681MeV(40%); 4.644 MeV(60%) Beta energy 1.1615 MeV (lOO%)
Gamma energy: given as "Weak". (Source: Radiochemistry of Bismuth Kashinath S. Bhatki Tata Institute of Fundamental Research
Homi Bhabha Road, Bombay 400005 and Bhabha Atomic ResearchC-entre Trornbay,Bombay 400085 (India)
Prepared for Subcommittee on Radiochemistry
National Academy of Sciences – National Research Council USA. via Los Alamos National Labs. at http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CDoQFjAA&url=http%3A%2F%2Flibrary.lanl.gov%2Fcgi-bin%2Fgetfile%3Frc000040.pdf&ei=WON3UeGFFsiKiQfvkoFY&usg=AFQjCNEMjupNgSA-NyDGPz6yyTslMqXajg&bvm=bv.45580626,d.aGc
12 Polonium 210 Alpha energy 5.304 MeV 99% Alpha 4.5 MeV (Source: As for Polonium 214)
How well do the radiological characteristics of Uranium and its decay series fit with the specifications for medical x ray?
Quote: “linear energy transfer (LET),the rate at which energy is transferred from ionizing radiation to soft tissue, expressed in terms of kiloelectron volts per micrometer (keV/μm) of track length in soft tissue. The LET of diagnostic x-rays is about 3 keV/μm, whereas the LET of 5 MeV alpha particles is 100 keV/μm.”
Of course, the energy of alpha and beta radiation is not constant. Toward the end of its range, such radiation has lost much of its energy. It is possible to construct experiments in which test tissue is placed at a distance from an alpha or beta emitter so that the tissue is subject to LET resultant from end of range energy deposition.
The question must be asked as to how nuclear industry proposes to control the LET, the dose and dose rate of radiation emitted by substances it releases in the biosphere. Unlike laboratory experimenters, who can turn x ray machines on and off, demonstrably the main mechanisms of control available to nuclear industry are decontamination by means such as steam cleaning, and lobbying government for lax and cheap regulation, including government decree of higher “allowable doses”.
This has resulted, for example, in Japanese children being subject to allowable accumulated radiation doses which match that allowed for adult radiation workers.
The concept of radiation being “good” or “bad” is false. If one dose deemed “good” is added to the accumulating lifetime dose, it can be seen that there is no benefit. It is just a dose. Just another dose.
Fukushima kids cop ‘lifetime’ radiation dose
Fukushima kids cop ‘lifetime’ radiation dose
By North Asia correspondent Mark Willacy
Updated July 12, 2012 14:42:02
A Japanese study has found some children who live near the Fukushima nuclear plant have received “lifetime” doses of radiation to their thyroid glands.
A team from Japan’s Institute of Radiological Sciences used government data to measure the internal radiation exposure of more than 1,000 Fukushima children.
The Fukushima nuclear power plant emitted radiation after being crippled by the March 2011 earthquake and tsunami.
Despite the government announcing more than half of the children had zero exposure, the independent study found that on average they did receive thyroid gland doses of internal radiation.
Several children were judged to have received an equivalent lifetime dose to the thyroid.
But the government says it does not plan to notify the parents out of fear of creating anxiety.
In fact there is strong evidence that industry is very keen to continue to enjoy information control enforced by government (in the US by way of the provisions and punishments enabled by the US Atomic Energy Act and related legislation) and also much cheaper and much more lax regulations, regulations which permit more nuclear pollution to be emitted by nuclear industry.