Posted on August 26th, 2009 460 comments
1. Experimental Evidence
1.1. Cancer Prevention
Bhattarcharjee in 1996 showed that when the mice preirradiated with just adapting doses of 1 cGy/day for 5 days (without a challenge dose), thymic lymphoma was induced in 16% of the animals (Bhattarcharjee 1996). Interstingly, when preirradiated mice were exposed to a 2 Gy challenge dose, thymic lymphoma was induced again in 16% of the animals. However, the challenge dose alone, induced thymic lymphoma in 46% of the mice. From these results, it can be concluded that the low dose preirradiation possibly cancel the induction of thymic lymphoma by the 2 Gy challenge dose. In 1996, Azzam and his colleagues showed that a single exposure of C3H 10T1/2 cells to doses as low as 0.1 cGy reduces the risk of neoplastic transformations. They suggested that a single low-dose at background or occupational exposurelevels, may reduce cancer risk. Recently, Redpath and his co-workers haveconfirmed the findings of Azzam and his coworkers (Azzam et al. 1996). To test the generality of the observations of Azzam and his colleagues, they used the Hela x skin fibroblast human hybrid cell. Using a similar experimental protocol, they demonstrated a significantly reduced transformation frequency for adapted to unirradiated cells (pooled data from four separate experiments).In addition, recently Mitchel and his co-workers in Canada have indicated that a low dose preirradiation (10 cGy, 0.5 Gy/h) modifies latency for radiation induced myeloid leukemia in CBA/H mice after exposure to a 1 Gy chronic radiation exposure (Mitchel et al. 1999). They showed that the latent period for development of acute myeloid leukemia (AML) was significantly increased by the prior low radiation dose. Interestingly, according to T.D. Luckey one third of all cancer deaths are premature and preventable by low-level ionizing radiation (Luckey 1994, 1997).
1.2. Survival Rate
In 1996, Yonezawa and his colleagues indicated that when 21-ICR mice were exposed to a 8 Gy of X-rays, about 30% of the animals survived 30 days after the irradiation. However, when mice preirradiated with 5 cGy of X-rays, the survival rate increased to about 70% (Yonezawa et al. 1996).
2. Epidemiological Evidence
Although radiation hormesis data are still incomplete, extensive epidemiological studies have indicated that radiation hormesis is really exist. A briefreview on this irrefutable evidence is as follows:
2.1. Japanese studies
1-According to UNSCEAR report (1994), among A-bomb survivors from Hiroshimaand Nagazaki who received doses lower than 200 mSv, there was no increase in the number of total cancer death. Mortality caused by leukemia was evenlower in this population at doses below 100 mSv than age-matched controlcohorts.
2-Mifune (1992) (Mifune et al. 1992) and his co-workers indicated that in a spa area (Misasa), with an average indoor radon level of 35 Bq/m3, the lung cancer incidence was about 50% of that in a low-level radon region. Their results also showed that in the above mentioned high background radiation area, the mortality rate caused by all types of cancer was 37% lower.
3-According to Mine et al. (1981), among A-bomb survivors from Nagasaki, in some age categories, the observed annual rate of death is less than what is statistically expected.
4-Kumatori and his colleagues (Kumatori et al. 1980) reported that according to their 25 year follow up study of Japanese fishermen who were heavily contaminated by plutunium (hydrogen bomb test at Bikini), no one died from cancer.
2.2. Background Radiation Studies
1-In an Indian study, it was observed that in areas with a high-background radiation level, the incidence of cancer and also the mortality rate due to cancer was significantly less than similar areas with a low backgroundradiation level (Nambi and Soman 1987).
2-In a very large scale study in U.S.A, it was found that the mortality rate due to all malignancies was lower in states with higher annual radiation dose (Frigerio 1976).
3- In a large scale Chinese study, it was showed that the mortality rate due to cancer was lower in an area with a relatively high background radiation (74,000 people), while the control group (78,000 people) who lived in anarea with low background radiation had a higher rate of mortality (Wei L 1990).
4-In the U.S.A., it was indicated that significantly, the total cancer mortalityis inversely correlated with background radiation dose (Cohen BL. 1993).
2.3. Nuclear Power Plant studies
1-In a Canadian survey the mortality caused by cancer at nuclear power plants was 58% lower than the national average (Abbat et al. 1983).
2-In U.K also it was indicated that cancer frequency among nuclear powerplant workers was lower than the national average (Kendal et al. 1992).
The Mechanism of Hormetic Phenomena
Although still we do not know the entire mechanisms of radiation hormesis, the following theories may explain this process:
1-DNA repair (Mollecular level)
According to this theory, low doses of ionizing radiation induce the production of special proteins, that are involved in DNA repair processes (Ikushima 1996). Studies using two dimensional gel electrophoresis indicated new proteins in cells irradiated with low doses of radiation. Also, it was further shown that cycloheximide, a protein synthesis inhibitor blocks this hormetic effect. The function and importance of these radiation induced proteins is still unknown. Also it was foud that inhibitors of poly ADP-ribose polymerase, an enzyme implicated in DNA strand break rejoining could prevent the induction of adaptive response (for a review see Wolff 1998).
2-Free radical detoxification (Molecular level)
In 1987 Feinendengen and his co-workers indicated that low doses of ionizing radiation cause a temporary inhibition in DNA synthesis (the maximum inhibitionat 5 hours after irradiation). This temporary inhibition of DNA synthesis would provide a longer time for irradiated cells to recover (Feinendengen et al. 1987). This inhibition also may induce the production of free radical scavengers, so irradiated cells would be more resistant to any further exposures.
3-Stimulation of immune system (Cellular level)
Despite the fact that high doses of ionizing radiation are immunosupressive, many studies have indicated that low doses radiation may stimulate the function of the immune system. In 1909 Russ first showed that mice treated with low-level radiation were more resistant against bacterial disease (Russ VK 1909).Later in 1982 Luckey published a large collection of references supporting immunostimulatory effects of low doses of ionizing radiation (Luckey TD 1982).Research Acute Myeloid Leukemia, Azzam, Cancer Deaths, Cancer Prevention, Cancer Risk, Experimental Evidence, Experimental Protocol, Generality, Gy, Hybrid Cell, Ionizing Radiation, Latent Period, Leukemia Aml, Low Radiation, Lymphoma, Radiation Dose, Radiation Exposure, Survival Rate, Thymic Lymphoma, Yonezawa Top
Posted on May 24th, 2009 2 comments
In 1980, Professor T.D. Luckey, a biochemist at the University of Missouri, published a study, entitled Hormesis With Ionizing Radiation (CRC Press, Boca Raton, FL; also in Japanese, Soft Science Inc., Tokyo), of over 1200 experiments dating back to the turn of the century reporting the effects of low-level radiation on biota ranging from viruses and bacteria through various plants and animals up to vertebrates. He found that, by all the criteria normally used to judge the well-being of living things, modest increases of radiation above the natural background make life better: they grow bigger and faster; they live longer; they get sick less often and recover sooner; they produce more offspring, more of which survive. The phenomenon of “hormesis”–whereby things that become harmful at high concentration are actually beneficial in small doses–is established in chemical toxicology. The effect is believed to result from stimulation and exercising of the natural immune system. What Luckey showed was that it applies also to radiation.
Some further facts that are consistent with this conclusion:
* Iowa, the state that the EPA found as having the highest average level of radon in the home, also has below-average cancer incidence. The mountain states, with double the radiation background of the US as a whole, show a cancer rate way below Iowa’s. Data from a study of 1729 U.S. counties shows the correlation between radon and lung cancer mortality to be about the same as for cigarette smoking; except that it’s negative: the more radiation, the less cancer.
* The same extends worldwide. The waters of such European spas as Lourdes, Bath, and Bad Gastein, known for their beneficial health effects since Roman times, all have high radioactivity levels. Areas noted for high radiation backgrounds, such as the Caucasus, southwest England, northwest India, have high longevity and low cancer incidence.
* British data on over 10,000 UK Atomic Energy Authority workers show cancer mortality to be 22% below the national average. For Canada the figure is 33%. (Imagine the hysteria if those numbers were the other way around!)
It appears, however, that the political consequences of announcing this to a public that has been saturated with contrary propaganda for over 20 years would be unacceptable. Although papers and conferences on radiation hormesis are now regular features of the scientific scene, they are ignored by the lawmakers and regulatory authorities. The continuing assumption of proportionate damage by tiny doses contradicts everything that has been discovered about cell metabolism and the mechanism of DNA repair since the early sixties.
If a little extra radiation is good for you, what optimum dose should our local health-food store recommend? Work reported from Japan puts it roughly at two “millirems,” per day. That’s about a tenth of a dental X-ray, or one coast-to-coast jet flight, or a year’s worth of standing beside a nuclear plant. For comparison, the level where the net effect becomes harmful is around two rems per day; 50 (note, we’re talking rems now, not millirems) causes chronic radiation sickness; 100 is lethal.
Perhaps tablets for those who don’t get enough regular exposure wouldn’t be a bad idea. A good way to use radioactive waste might be to bury it under radon-deficient homes. And perhaps cereal manufacturers should be required to state on their boxes the percentage of the daily dietary requirement that a portion of their product contributes. After all, if radiation is essential for health in minimum, regular amounts, it meets the accepted definition of a vitamin!
As a further note to put things in perspective, her are some figures comparing radiation exposures experienced by the average American from various sources, natural and man-made.
Annual estimated doses in mREMs per year:
All rocks contain traces of uranium. Radiation from the granite used in Grand Central Station exceeds the NRC limits for nuclear-plant operation. Grand Central Station wouldn’t get a license as a nuclear plant. Neither would the piers of the harbor at Dun Laoghaire, near where I live in Ireland.Nuclear, Radiation Hormesis Atomic Energy Authority, Bad Gastein, benefits, Cancer Incidence, Cancer Rate, Chemical Toxicology, Cigarette Smoking, European Spas, Ionizing Radiation, Level Radiation, low level radiation, Lung Cancer Mortality, Natural Immune System, Northwest India, Plants And Animals, Radiation Background, Radiation Hormesis, Radioactivity Levels, Soft Science, Southwest England, Uk Atomic Energy Authority, Viruses And Bacteria, vitamin R, Worke Top