November 1996

Sadao Hattori

(CRIEPI-Japan)

                "In 1982, Thomas D. Luckey, Prof. Emeritus, University of Missouri published a paper on radiation hormesis. His emphasis was on the beneficial effects of low-level radiation contributing to a healthy body, longer life, vitalization, etc.^1,2

                "Radiation hormesis research by the Central Research Institute of Electric Power Industry in Japan was initiated on the rationale that if Luckey's claim were true, radiation management in Japan was extremely erroneous and the research institutes had to determine the truth.

                "Obtaining many test results from some human data and various animal experiments on the health effects of low-level radiation that support the radiation hormesis hypothesis,^3,4 we decided to expand our research activities into a collaborative testing program with 14 universities and 2 other institutes on various subjects.

                The subjects in which we are now interested are as follows:

                1. enhancement of molecular biological activities such as gene repair and apoptosis by low-level radiation

                2. enhancement of the immune system such as the ratio of Helper T cell/Suppressor T cell by low-level radiation

                3. rejuvenation such as cell membrane permeability, super- oxide dismutase activity, and the therapy of old-age diseases such as diabetes and high blood pressure.⁵

                "Results obtained through the research program, including analytical hypotheses that are simulated by up-to-date information sent from scientists worldwide, are leading us into an exciting stage of the program. Sakamoto of Tohoku University Hospital is achieving great success in the therapy of non-Hodgkins lymphoma. He has applied 10 cGy of X rays to the whole body three times per week for 5 weeks. Ohnishi of Nara Medical University tried to find the rationale for this, obtaining many data of the tumor suppressor gene p53 stimulated by a 10- to 50-cGy dose to rats and mice.⁶

                "Yamada is confirming various effects to the neurotransmitting system in the application of low-level radiation.

                "We are certainly recognizing the radiation hormesis asserted by Luckey. Furthermore we are very interested in the discussion of health effects of low-level radiation discussed at the annual conference of the Society of Nuclear Medicine in Denver in June 1996. The damage and repair of DNA by natural background radiation is much smaller than the natural damage and repair of human cells caused by daily biometabolism. The double strand breaks of DNA in each cell under normal biometabolism take place 10^– times in a year. The double strand breaks of DNA in the same damage mode as radiation take place 10⁵ times per cell in a year. The double strand breaks by natural radiation are analyzed to take place <10 times per cell in a year. Then, from the standpoint of DNA damage, the radiation damage of a human cell can become the same level of damage by normal biometabolism by being exposed to 10 Gy/yr, in the case of low linear energy transfer chronic dose. This 10 Gy/yr is an extremely interesting coincidence with the ZEP of Luckev's dose response figure in his 1991 book.

                "On this issue, I address the question, Why are you obtaining your clear hormetic data on your animal tests generally applying very small doses such as 5 cGy? The answer is as follows: We are interested in the enhancement of DNA repair activities and apoptosis being stimulated by a small dose, which is given in less than a few minutes by a dose rate >1000 times higher than 10 Gy/yr.

                "Many kinds of simulative response of molecular organisms by low-dose radiation and the various biophysical responses by low-dose radiation ^7,8 suggest to us an unknown and extremely comprehensive and meaningful field of research and human benefit."

1. T. D. LUCKEY, "Physiological Benefits from Low Levels of Ionizing Radiation," Health Phys.. 43. 6 (1982).

2. T. D. LUCKEY, Radiation Hormesis. CRC Press, Boca Raton, Florida (1991).

3. Proc. Int. Conf. Low Dose Irradiation and Biologicl Defense Mechanisms, Kyoto, Japan, 1992.

4. M. MIFUNE et al., "Cancer Mortality Survey in a Spa Area (Misasa, Japan) with a High Radon Background." J. Jpn Cancer Res..83 (1992).

5. K. YAMAOKA, "Increased SOD activities and Decreased Lipid Peroxide Level in Rat Organs Induced by Low Dose X Ray Irradiation," Free Radical Biol. Med.. 11, 3 (1991).

6. T. OHNISHI et al., "Accumulation of Wild-Type p53 Protein in Various Organs of Rats After Whole Body Exposure to Low Dose X-Ray Irradiation" (in preparation).

7. S. KONDO, Health Effects of Low Level Radiation, Kinki University Press and Medical Physics Publishing. Madison, Wisconsin (1993).

8. S. HATTORI, "State of Research and Perspective on Radiation Hormesis in Japan," Int. J. Occupational Med. Toxicol.. 3, 2 (1994).