Professor and Chairman Emeritus Dr. T.D. Luckey of the Department of Biochemistry in the U. Missouri-Columbia School of Medicine, states (1995) that: The beneficial effect of low dose irradiation was discovered in 1896 when Shrader inoculated Guinea pigs with diphtheria bacillus. Unexposed controls died within 24 hours. Animals exposed to X-rays before inoculation survived. Also, 2 series of 4,000 male mice were exposed daily to different doses and dose rates of 60-Co gamma radiation. When half of the unexposed mice had died, the survival of most of the exposed mice was greater than that of the control groups. The average lifespan of the irradiated groups tended to be longer. The lowest dose rate for these healthy mice, 7 mGy/d, is about 800 times greater than that recommended for humans, 5 mGy/y. Note also, 83% of the mice which received 6.3 cGy/d, a total of 1620 cGy, were alive when 50% of the control mice had died.

Professor Luckey also reports (1994) that: Many studies showed that chronic, low level gamma ray exposure increased growth rates in mice, rabbits, and guinea pigs. Injection of 20 to 60 kBq of U-238 or Ra-226 significantly increased the growth rate of mice. Mice from dams given tritiated water produced offspring which grew at faster than controls. Chronic exposure of over one million salmon stimulated growth with 0.54 cGy/d, and the weight of individual fish which returned after 4 years in the Pacific was greater. The weight of unexposed fish from lightly exposed fathers that returned after three years was 117% more than controls. A greater proportion of exposed fish and unexposed fish from exposed fathers returned. This transferral of something to the second generation was noted in duckweed. Rats showed immediate and sustained higher growth rate following 2 Gy of X-rays; and 0.5 to 2.0 cGy of X-rays also increased growth rate and maturation. The height of burro foals exposed to 2.5 Gy of gamma radiation was significantly greater at 2 years. Chick growth was accelerated by exposure to 5 to 10 Gy of gamma rays, confirmed (at) 6.4 Gy. Chicks from eggs exposed to 6.4 Gy of gamma rays grew faster. Fish embryos exposed to 0.15 to 15 Gy of X-rays grew faster. Carp sperm exposed to 5 Gy gamma rays increased the survival of young to marketable size, and 128% larger.

Professor Luckey reports (1994) on the subject of radiation effects on reproduction that: 'Superovulation' and 'superimplantation' were used to explain the increased litter sizes from rats exposed to 2.5 or 5 Gy X-ray, supporting the Manhattan District Project study with rats exposed to uranium dust: more young were produced from exposed rats. Rats exposed to 2 cGy/d of gamma rays through 13 generations, in generations five to ten, cast litters at 120% of controls; the average number of young per litter was 148%, and the mean weight of newborn was 108%. The weight of individual young weaned, and the percent weaned, was less in the exposed colonies, which was expected because the limited milk supply was shared by more young. However, the number weaned per dam averaged 4.9 in the control group and 5.1 in exposed groups. In the 12th generation, litters from 4 pregnancies, the exposed females that cast litters was 117% of controls, the average litter size was 157%, average weight of pups was 110%, total weight of the litter was 172%, average number weaned was 147%, and the total weight of young at weaning averaged 137% of controls. When exposed from weaning through breeding to 1 cGy/d, mice had shorter generation times, higher birth rates, and, subsequently, a greater rate of population increase than controls. Male mice exposed to a single dose of 0.2 to 1.6 Gy X-ray produced increased numbers of newborn; as when both sexes were exposed to 2 Gy from X-rays for 25 generations.

H. Wade Patterson, former Editor of Health Physics Journal, quotes (1996) Spalding et al, 1982: Male mice were exposed for 82 generations. Most irradiated animals lived longer or no differently than controls; however, in several cases differences were significant. Newborn mice exposed to 180 rad at 0.07 R/day had significantly longer life span. At all dose levels the 2-month age group lived significantly longer than the median controls. There were no differences among the 6-month-old mice, but the 15 month group with the 20-rad dose lived significantly longer. Data over widely ranging dose, exposure-rate, and exposure-age conditions fail to support radiation-induced life shortening from radiation approaching background levels. In fact, the data suggest beneficial effects from low-dose and low-dose-rate gamma-ray exposure.

Dr. Harold Boxenbaum reports (1992) that: "Further support that radiation produces longevity hormesis is (from) chipmunks living in the wild. The animals were live-trapped, irradiated with either a single-dose of 200 or 400 Roentgens gamma-radiation, except for controls, and then returned to the wild. (The) exposure, within the dose-range utilized, enhanced longevity. "

In an abstract, Dr. Ishii and colleagues report on reduced thymic lymphoma in Radiation Research (1996) that: "Male AKR mice were irradiated with 5 cGy three times a week or 15 cGy two times a week from 11 weeks of age for 40 weeks. The incidence of thymic lymphoma was 80.5% in sham-irradiated mice, 67.5% in mice irradiated with 5 cGy three times a week and 48.6% in mice irradiated with 15 cGy twice a week."

Dr. Hugh F. Henry, of the Oak Ridge National Laboratory, states (1961) that: Both mice and guinea pigs exposed to 0.11 r/day of radium gamma increased their average life span by about 7%. With only a few rabbits, average life spans were increased about 18% with doses of as much as 2.2 r per day. Co-60 doses of 0.8 r/day result in a 20% increased average life span for rats kept at temperatures of 50C and 25C. Male rats kept at 28C and 35C, with dose rates of 2.5 r/day, have higher life expectancy. Mice exposed to a single short-term dose of about 15 r of x-rays early in life increased lifespan, whereas a similar 30-rad exposure decreased life-span. Female mice exposed on a 23-hour daily basis to 1 rad/day have an increased average survival age of some 4%. In 730-day-old mice having a normal life expectancy of 875 days with doses of 275 r and 550 r, the last survivors of each of the irradiated groups lived longer than any of the controls.

Drs. Yoshio Hosoi and Kiyohiko Sakamoto of the Tohoku University School of Medicine discuss (1997) TBI effects on metastasis: "Low dose total body irradiation (TBI) (was shown to) suppress metastasis using both artificial and spontaneous lung metastasis in WHT/Ht mice... Injection of tumor cells irradiated with 10-50 cGy in vitro showed no difference from the control value, which indicated that the suppressive effect of the low dose TBI was based on the radiation effect on mice but not on tumor cells."

Dr. U. Yamamoto of the Faculty of Life Science at the Yasuda Women College in Hiroshima and Dr. T. Seyama of the Radiation Effect Research Foundation, Hiroshima discuss (1997) HTO ingestion in mice: "(By) continuous oral administration of HTO on mice weight-selected (24 ± 1 g) at 10 weeks, the total tumour frequency was decreased from 80% to 50% at about 3.6 mGy/day. The linear line crossed to the base line at 12 mGy/day which is a threshold dose-rate (essential threshold dose-rate). However, this linear line has a tailing (which) becomes linear in normal scale. This linear line crosses to the base line at 9 mGy/day which is another threshold dose-rate (tail threshold dose-rate). The relationship between life-shortening and dose-rate is also linear with a tail in semi-log scale. Two mGy/day was found to be the essential threshold dose-rate and 0.2 mGy/day the practical tail threshold dose-rate. There exists two types of threshold dose-rates, essential and practical, not only in the frequency of thymic lymphoma but also in the life-shortening. In the case of gamma-irradiation, a similar pattern resulted when the data presented by Lorenz et al (1954) and modified by Failla and McClement (1957) and those presented by Grahn et al (1969) and averaged by NCRP (1980) were plotted, the essential and the practical threshold dose-rates being 20 mGy/day and 2 mGy/day. It is clear that the effect of 3-H beta-rays is greater than that of gamma-rays.

Dr. P.C. Kesavan of the Bhabha Atomic Research Centre in Trombay, India, reports (1997) on HBRA studies of rats that: The black rats, the 800th to 1000th generation in the High Background Radiation Areas (HBRAs), received about 7.5 times greater radiation dose than controls. It was stated: 'whereas our findings thus give no positive indication of genetic damage to the rats living on the strip, they do not rule out the possibility of induced mutations lurking beyond the reach of our method.' Based on work with laboratory mice, the minor skeletal variants in Kerala rats are overwhelmingly influenced by non-genetic factors. The view that the lack of positive evidence for possible enhancement of mutation frequencies by low chronic exposures is the choice of inappropriate parameter is not supported by mutagenesis in crop improvement. Polygenic mutations with epigenetic interactions are more readily induced by ionizing radiations. The statistical methods employed are good enough to detect the polygenic mutations if these are really induced by chronic low level exposures.

Dr. Philippe Duport of the Institute for Research on Environment and Economy, University of Ottawa, Canada and his associates report (1997) that: "From the limited set of laboratory data on the induction of lung cancer in laboratory rats it appears that, at low exposures, the risk of lung cancer decreases with decreasing concentration, and that exposures of the order of 25 WLM, at an exposure rate of 2 WL do not produce any excess lung cancers. The disappearance of lung cancer risk in animals, at the exposure of 25 WLM, when the exposure rate is decreased from 100 to 2 WL, illustrates the role played by dose rate in the induction of lung cancer by alpha emitters. This observation is in line with the fact that the inverse dose rate effect seen at exposures of several hundreds WLM disappears when the cumulated exposure decreases (Gilbert 1996)"

Dr. M. Delpoux of the University Paul Sabatier in Toulouse, France, and associates in France and Belgium, report on an HBRA in France (1997) that: In South-West France the gamma radioactivity ranges generally from 0.001 to 0.030 x 10^-2 mGy/hr, and dose rates as high as 1 x 10^-2 mGy/hr are not uncommon. ...During 20 months exposed rabbits received from 36,300 up to 130,750 mGy, whereas controls received 2,400 mGy... structural chromosome anomalies typical of an exposure to ionizing radiation (chromosome fragments, dicentric chromosomes) increase initially but disappear completely after 20 months... Male mice received from 13,800 mrad up to 63,250 mrad, and concurrent controls from 34 to 127 mrad according to the duration of exposure. The number of litters and of offspring sired after exposure during 6 months was clearly related to the dose of gamma irradiation received, a dose-related increase up to 45,080 mrad, falling abruptly for the animals receiving 63,250 mrad.