I’ve been editing my book on Fukushima and the Privatization of Risk.
I've blogged on it here:
Dec 17, 2012
Fuksuhima and the Privatization of Risk: Introduction. Every morning I look at the Fukushima webcam and I wonder at what I am seeing. I see strange brownish-purplish colors in vertical shafts, auras of blue-green, and ...
Dec 18, 2012
Fukushima and the Privatization of Risk 2: What is the Privatization of Risk? In the summer of 2012, the Japanese Diet issued a report chaired by Kiyoshi Kurokawa, a professor emeritus at the University of Tokyo, sharply ...
This is my IV Installment. It is based on a chapter I wrote on radiation and risk for my book.
In the chapter, I provide a chronology of how radiation became linked to health risks across the 20th century. In 1928 it was known that Xrays damaged the chromosomes of fruit flies. By the 1940s it was known that ingested radionuclides cause wasting disease and cancer. In 1956 geneticists concerned about the effects from atmospheric testing warned that acquired genetic mutations are heritable through germ line cells.
It was known in 1956 that each new generation acquires each of their parents’ germ line cell mutations. Mutations may remain relatively “silent” or undetectable, exerting subtle influences on health and longevity. Eventually, however, the total level of mutations may cause relatively sudden reproductive failure across a few generations. No one knows when that time will occur, the geneticists warned at that time.
Now we know that atmospheric testing did cause cancers and leukemia. The question of exactly how many remains unclear. Also unclear are the precise figures (or sometimes even ballpark figures) for the range of diseases caused by all the significant radiation disasters to have occurred across since World War II, both deliberate and accidental.
Does atmospheric release of radiation cause significant up ticks in mortality statistic for newborn animals, ranging from birds to human infants? There are studies that indicate an affirmative answer to this question.
Today scientists concerned about the effects of ionizing radiation and chemicals on human health have new tools for examining genetic and epigenetic effects in laboratory conditions. What happens to human DNA when transversed by an alpha particle? Electron microscopes allow us to see how DNA is severed by an alpha particle. What are the implications for that genetic strand’s future production of proteins? Gene expression assays enable analysis of genotoxic and nongenotoxic responses (Marchant p. 14).
The research is fascinating and it promises to upend our previous understandings of dose-effects. Previously it was believed that dose-effects were linear, with higher doses cause more significant effects incrementally. However, now we know that linear and unidirectional relationship is not always correct.
The study of proteomics through gene expression assays has raised new questions about low-level dose effects, particularly at biologically vulnerable periods in development. Proteomics investigates the processes that can affect protein production other than the actual DNA sequence. It turns out that much DNA sequence can produce a variety of proteins depending upon a complex system of "epigenetic" signaling that activates and silences stretches of DNA.
Epigenetic processes are, unfortunately, very vulnerable to disruption. For instance, chemical endocrine disruptors (found in plastics, cosmetics, etc) can have significant effects across a range of doses and large effects can be seen from small doses during vulnerable times in development (Smith and Robert, 231). The idea of a dose-effect relationship where larger doses produce more severe effects does not hold for endocrine disruptors.
What are the epigenetic effects of ionizing radiation? Research has established the disruptive effects of radionuclides on DNA as new technologies reveal that a single alpha particle can break DNA. The next question is, what effects do various forms of ionizing radiation have on the epigenetic processes governing protein production? How much time can elapse before changes in epigenetic processes cause problematic mutations? This is an emerging field of research and it is fascinating and important for its implications for the human genome.
The human genome is our genetic heritage. We have evolved under the sun’s ionizing radiation and the mutations caused by it and other sources of exposure, such as radon gas, have contributed to our evolution across time. That said, its important to recognize that the vast majority of mutations are deleterious, rather than beneficial, as they convey no immediate benefits and are more likely to increase biological risks. So, any significant increase in the rate of our mutations is not likely to be beneficial within our lifetime, nor across generations.
Mutations can accumulate rapidly if each generation continues to experience high levels of exposure to radiation, particularly if the exposure is from ingested radioisotopes like radiocesium, strontium, uranium, and plutonium. Indeed, the research on Chernobyl and other areas of the world highly contaminated by ionizing radiation suggest that terrible birth defects are possible within relatively short periods after exposure. The true scope of disease and disability across generations of exposure from Chernobyl and other accidents are unknown. Time and dedicated researchers are required to know with any certainty.
What can be concluded is that the currently used risk models may under-predict the range and frequency of diseases because their frequency tables are based on statistics that now have to be called into question. The statistics currently in use primarily rely on clinical findings of somatic changes to document dose effects.
New findings call into question the linear dose-effects model. Small amounts may have significant effects at critical times, especially in early development. Small amounts may also have genotoxic effects across time, the research on delayed and bystander effects conclude. In essence, the clinical approach to documenting and predicting dose-effects may lack predictive validity.
One especially relevant findings for human reproductive health is the discovery that mitochondrial DNA is particularly vulnerable to disruption by ionizing radiation, even among people acculturated to relatively high levels of natural (not human produced) background exposure. What might rapid increases in human produced radioisotopes have on human mitochondrial DNA? No one knows for sure.