GENETIC EFFECTS OF IONIZING RADIATION
A concern often expressed by Atomic Veteran survivors regard the genetic effects for first and second generation offspring of exposed veterans.
Research and statistics show a definite increase in the incidence of inherited chromosomal damage resulting from even low doses of radiation exposure.
A recent 1999 Institute of Medicine study funded by the Department of Veteran’s Affairs has determined that an epidemoligical study of the adverse reproductive outcomes of families of Atomic Veterans is not feasible.
The committee making this determination included the reasons as:
- “Insurmountable difficulties in finding and contacting a sufficient number of atomic veteran offspring and establishing accurate measures of radiation exposure of atomic veterans.”
- “Inability to identify and document effects over a 50 year interval: and limiting factors such as study size, population composition and uncertain exposure levels.”
They did however feel confident in the feasibility of a study of residents and children in areas of high natural radiation levels, or of people living near nuclear installations and non-military individuals exposed to fallout from atmospheric tests.
Attempts to prove that anomalies effecting Atomic Veteran offspring fall into the category of “radiation induced” or “naturally occurring”, is presently a debatable issue. There is no stamp on genetic anomalies that says “radiation induced” or “naturally occurring”. As scientific techniques develop and public awareness and concern increases, the future may present answers regarding genetic effects of radiation exposure…..
But today we have not been provided with any uniformly accepted scientific methods of proof.
UNIVERSITY OF CALIFORNIA
Study Shows Hereditary Legacy of Radiation Exposure
November 4, 1997
Ever since the atomic bombs dropped on Japan created the world’s largest experiment on the effects of radiation on humans, people have puzzled over not only just what these effects could be, but also if they could be passed on to the children of those exposed. In the past, researchers have shown in mice that some effects — in the form of genetic mutations — can indeed be passed to offspring and cause health effects.
Now Lynn Wiley and her colleagues at the University of California, Davis, and Lawrence Livermore National Laboratory have used a very sensitive model they developed to demonstrate that if a male mouse is exposed to radiation, he may pass on detrimental effects not only to his children, but also to his grandchildren, and even great-grandchildren.
Wiley will present her work at a conference Nov. 8-9 in Japan called “Bioregulation of Radiation Response: Genetic Instability.” Most of the information she presented was published this summer in the journals Radiation Researchand Mutation Research.
Wiley says that her “environmentally relevant” assay — using amounts of radiation that compares to what a person might receive during radiation therapy for cancer — confirms what the Japanese haves been saying for years; that the effects of radiation can be passed down through generations. Her results are controversial but she says, “so far, no one’s been able to knock it down … Every molecule of that paper has been turned over, and it hasn’t been shot down.”
“There is a big difference between transmission, which means passing on effects to the children, and heritability, which means passing it on to all future generations,” said Wiley, a professor of medicine with the campus Institute of Toxicology and Environmental Health. “Heritability means that it has survived a complete round of DNA replication, and that it is stable in the DNA of the sperm.”
The method that Wiley and her colleagues used is much more sensitive than those used in conventional mouse studies, which use hundreds of thousands of mice. Hers uses only about 75 mice at a time. According to Wiley, what is new about her findings is that she saw the radiation effects in the small numbers of mice she used, indicating that the radiation is affecting DNA non-specifically; in other words, it’s affecting many genes.
Wiley exposed eight or so male mice at a time to the radioisotope Cesium-137, and allowed these mice to mate with females once a week for eight weeks, to cover the sperm-making history of the father. The sons of these irradiated fathers were allowed to mate with females beginning at eight weeks of age to produce the grandchildren that were used in Wiley’s study.
In the assay developed by Wiley more than 10 years ago, embryos consisting of only four cells are removed from the mother. These cells are then combined with four cells from another embryo — one without a history of radiation — and allowed to multiply several times. Then the scientists count the total number of cells (one of the embryos has a special marker so it can be distinguished from the other). If there are fewer cells from the cells that received radiation, then they have a growth disadvantage from inherited DNA damage, according to Wiley.
Wiley said she found a significant reduction in cell reproduction and growth in the offspring of mice that had been irradiated six or seven weeks before conception, corresponding to a sensitive stage in sperm development. These grandchildren mice also weigh less than normal mice and their sperm are less efficient at fertilization.
Wiley suspects her fairly simple, yet exquisitely sensitive, cellular assay could be used to predict inherited effects of radiation in future generations of animals. The reproductive toxicology professor is now continuing her studies to look at lower doses of radiation, and to determine on a genetic level what the changes are that are induced by radiation.
“The human side of these studies is that we already have in mice documented irradiation effects that are passed on to future generations, ones that are causing cell growth and reproduction changes,” she said. “If you mess around with that, you can’t help but wonder if these changes will turn out to be cancerous or impair reproduction.”
Wiley’s work was funded by the National Institutes of Health.
CANCER RISK TO CHILDREN OF EXPOSED PARENTS
July 20, 1999 By Dick Ahlstrom, Science Editor
The children of a person who is exposed to radiation could be susceptible to cancer as a result, according to research carried out in Britain. Even low levels of radiation could cause mutations that cross the generational divide and could be detected in offspring.
“We did not expect these results,” said Dr Yuri Dubrova, Wellcome Trust Senior Lecturer in the Department of Genetics at the University of Leicester, who yesterday presented his research at the 11th International Congress on Radiation Research under way in Dublin. “We finalised them two weeks ago and we checked them twice.”
Dr Dubrova and colleagues were looking at mice exposed to nuclear radiation and watching for signs of cell mutations in their offspring. They were looking in particular at small segments of the genetic blueprint known as “microsatellites” which are very susceptible to mutation.
The researchers found the offspring of exposed male mice had six times the rate of mutation compared to mice that had not been irradiated. “We are dealing with an enormous increase in the mutation rate,” he told a conference session at University College Dublin yesterday.
The radiation causes a phenomenon known as “genomic instability”, a tendency for genetic material in the cells to recombine to cause unpredictable mutations that in turn could cause cancers. This subject is under intense study at the Radiation Science Centre of the Dublin Institute of Technology, organisers of the week-long conference which has brought 1,200 delegates to Dublin.
Exposure to radiation caused an increased probability of blood disorders such as leukaemia in subsequent generations, according to research by Dr Brian Lord and colleagues of the Paterson Institute for Cancer Research at the Christie Hospital, Manchester. There was a considerable increase in incidence of the disease in these offspring compared to unirradiated control groups, he said.
The data suggested it was not caused by direct inheritance but by an increased likelihood of genomic variability passed on to the next generation.
Earlier, a number of researchers presented data which tried to demonstrate the effects of genomic instability and the changes it caused in test mice. Dr Bob Ullrich, of the University of Texas in Galveston, described his work which attempted to answer the question “What does radiation do to ultimately lead to cancer?”
Their test results were able to separate the damage caused directly by the radiation exposure and the changes brought about due to genomic instability. They cultured cells that were changed because of it. They then studied what genes might be involved and whether there was a genetic component to this instability.
Dr Anders Wennborg and colleagues of the Karolinska Institutet in Sweden and the Bo Lambert company described studies of chromosomal damage that arose many days after exposure to radiation. These changes were linked to instability and not to direct mutations caused by the radiation. The data he said were “strongly indicative of a progressive aberration” in the genome.
“Negligible” Personal Risks vs Large National Rates
The fact, so seldom explained by radiation enthusiasts and so often stressed in our publications, is that extra exposure of a population to low-dose radiation creates only a small risk per individual, but it creates a real rate (not a “maybe”) of fatal radiation-induced cancer for the population.
For example: In 1990, the government-sponsored BEIR Report (p.172) estimated that if the population received an extra 100 milli-rems of dose every year (approximately equivalent to doubling the natural “background” rate), the dose-increment would induce extra cancer fatality in one out of every 400 people per lifetime (details available in Gofman 1995, Pt.3). Per newborn individual, the extra lifetime risk would be 1 chance in 400 — perhaps a “negligible” personal risk in some people’s opinion. The same estimate translates into a lifetime rate of 650,000 extra fatal radiation-induced cancers for a population of 260 million persons (USA). Our own 1990 estimate (Gofman 1990, Table 16-C) is about 7.6 times higher: 4,940,000 extra fatal cancers — 1 person in every 53.
Nonetheless, many radiation enthusiasts are arguing that the consequences of doubling the “background” dose would be “negligible” or “non-existent” or maybe “beneficial.” (For instance, see Billen 1990, or Graham 1996, or Pomeroy 1996, in the Reference List.)
By contrast, we and others find decisive evidence that there is no threshold dose for radiation-induced cancer. And this finding very strongly supports the presumption that inherited afflictions are also inducible by ionizing radiation, even at the lowest possible dose and dose-rate.
In our own view, it is quite possible that a permanent doubling of the “background” dose of ionizing radiation, worldwide, would very gradually double mankind’s burden of inherited afflictions — from mental handicaps to predispositions to emotional disorders, cardio-vascular diseases, cancers, immune-system disorders, and so forth. Such a doubling would be the greatest imaginable crime against humanity.