Posts
One of the landmark studies on genomic instability was published in 1992 by Eric Wright, Munira Kadhim, and colleagues [1]. In the course of their research, they exposed stem cells from the bone marrow of mice to plutonium-238, giving them a dose of from 0 to 5 grays of alpha radiation.
"The cells were kept in Petri dishes for 11 days until they had divided between 10 and 13 times, each producing between 10 000 and 100 000 daughter cells. Wright found that the progeny of the irradiated cells contained three and a half times as many chromosome aberrations as the descendants of cells that were not irradiated. In a letter to Nature, he concluded that the “relative biological effectiveness” — a measure of how damaging low-level radiation can be in the body — for isotopes that emit alpha particles is “effectively infinite” [emphasis added]" [2].
In the fall of 1995, more than thirty radiation biologists and health specialists attended a workshop in Helsinki to discuss the health consequences to the public of radiation-induced genomic instability. When compiling the available published information on genomic instability, attendees cited twenty-six studies that suggested that the “accepted rules for calculating the biological impact of radiation should be rewritten” (Edwards). According to Jack Little, professor of radiobiology at the Harvard School of Public Health and an attendee of the workshop: “Genomic instability changes our way of thinking about how radiation damages cells and produces mutations.” After the workshop, participants prepared a report for the World Health Organization. This report was never published. However, the magazine New Scientist acquired a copy and published excerpts. Included in the report was the observation that genomic instability is a key event not only in the process leading to cancer but to the development of other diseases as well. This insight is revolutionary. If confirmed, it will effectively destroy current concepts of radiation safety.
"Instability is also a “plausible mechanism” for explaining illnesses other than cancer, the report says. “It would seem likely that if genomic instability led to health effects these would not be specific but may include developmental deficiencies in the fetus, cancer, hereditary disease, accelerated aging and such nonspecific effects as loss of immune competence.” Epidemiology would be “powerless” to detect any relationship between the incidence of such diseases and exposure to radiation, the report says, because the number of people who would suffer any single disease would be too low. [Keith] Baverstock, who was the main organizer of the Helsinki workshop, and Wright believe that the world should be more wary of low-level radiation. If genomic instability is causing unpredicted disease, and if some people are genetically predisposed to it, the regulatory system starts to look inadequate. Existing measures meant to protect people, argue Wright and Baverstock, are less than reassuring" [3].
In response to these observations, people who support the reigning ICRP paradigm will argue that any illness induced by genomic instability will already be accounted for within existing safety limits. This position is untenable. It is based on the unfounded assumption that the frequency of all possible endpoints of radiation damage (not just cancer) are linearly related to dose and valid extrapolations about low internal doses of radiation can be made from high doses of radiation delivered exterior to the body. According to the model of radiation effects upheld by the nuclear establishment, cancer is the fundamental endpoint of concern following radiation exposure. Further, the frequency of cancer expressed in a population after exposure is directly related to the dose of radiation received by that population. In sharp contrast, as illustrated in the quotation above, radiation-induced genomic instability may produce “developmental deficiencies in the fetus, cancer, hereditary disease, accelerated aging and such nonspecific effects as loss of immune competence.” This hypothesis is revolutionary and in direct conflict with mainstream adherence to the belief that radiation damage to the human organism is confined to cancer. If this proves to be the case, it is totally without justification at this point in time to assume that these results are similarly in a linear relationship to dose and that current standards of safety protect the population from these endpoints. As has already been discussed, dosage is too imprecise a concept to account for radiation-induced changes on the cellular level from low levels of radiation. The number and rate of charged particles passing through the cell is a more fundamental phenomenon. This shift of perspective is essential for explaining newly discovered cellular effects of radiation.
The subject of depleted uranium will be explored in depth in subsequent chapters. But one observation is relevant at this point. Within the currently accepted framework for understanding radiation effects, battlefield dispersal of depleted uranium cannot possibly pose a radiological hazard. The “dose” of radiation is just too small. But in the light of current research, this point of view is no longer defensible. Two in vitro studies were recently conducted involving exposure of human osteoblast cells to depleted uranium. Both studies demonstrated that depleted uranium induces genomic instability in the progeny of cells receiving exposure. One study exposed cells to uranyl nitrate created from various isotopes of uranium and compared their toxic effects to cells exposed to the heavy metals nickel and tungsten [4]. Those cells exposed to DU evidenced an increased frequency of dicentric chromosomes — chromosomes with two centromeres — when compared to the nonradioactive metals. Further, the frequency of dicentric abnormalities was dependent on the specific radioactivity of the different isotopes. The conclusion was that it was alpha radiation emitted by uranium that induced the chromosomal aberrations. According to Miller and her colleagues, “Published data from our laboratory have demonstrated that DU exposure in vitro to immortalized human osteoblast cells (HOS) is both neoplastically transforming and genotoxic.” A second study conducted by the same research team exposed osteoblast cells to gamma radiation and alpha radiation from depleted uranium and compared the effects to nickel exposure [5]. Cell lethality and micronuclei formation were measured at various times after exposure. (Micronuclei arise from DNA double-strand breaks that are not rejoined. These have been implicated in carcinogenesis.) It was found that DU stimulates delayed reproductive death and the production of micronuclei up to thirty-six days (thirty population doublings) after exposure. This is evidence of induced destabilization in the genome. In contrast, the cell populations exposed to gamma radiation returned to normal after a period of twelve days. Further, micronuclei formation from DU exposure occurred at a greater frequency than for equal doses delivered by gamma irradiation. The authors summarized their results as follows: “These studies demonstrate that DU exposure in vitro results in genomic instability manifested as delayed reproductive death and micronuclei formation.” Together these two studies demonstrate that the alpha radiation emitted from depleted uranium can damage DNA and that DU can induce instability to the genome that initiates abnormal growth in progeny cells. Only in political defiance of these observed phenomenon can propagandists continue to affirm that depleted uranium poses no radiological hazard.
Bibliography
[1] Kadhim M.A., Macdonald D.A., Goodhead D.T., Lorimore S.A., Marsden S.J., Wright E.G. Transmission of Chromosomal Instability after Plutonium Alpha-Particle Irradiation. Nature. 1992; 355:738-740.
[2] Edwards R. Radiation Roulette. http://msowww.anu.edu.au/~peterson/HCarticle106.html
[3] Edwards R. WHO ‘Suppressed’ Scientific Study Into Depleted Uranium Cancer Fears in Iraq. Sunday Herald Online. February 22, 2004. http://www.sundayherald.com/40096.
[4] New Scientist. No. 2103. October 11, 1997. pp. 36-40.
[5] Miller A.C., Xu J., Stewart M., Prasanna P.G.S., Page N. Potential Late Health Effects of Depleted Uranium and Tungsten Used in Armor-piercing Munitions: Comparison of Neoplastic Transformation and Genotoxicity with the Known Carcinogen Nickel. Military Medicine. 2002a; 167(Supplement 1):120-122.
[6] Miller A.C., Brooks K., Stewart M., Anderson B., Shi L., McClain D., Page N. Genomic Instability in Human Osteoblast Cells after Exposure to Depleted Uranium: Delayed Lethality and Micronuclei Formation. Journal of Environmental Radioactivity. 2003; 64:247-259.
