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No safe dose

By Bill Williams - posted Tuesday, 12 December 2006

The recent zeal among conservative politicians for expanding Australia’s nuclear industry should raise questions about its potential impact on the health of humans and their habitat. Unfortunately, the recently released Switkowski Report (pdf 3.63MB) on Uranium Mining Processing and Nuclear Energy brings little serious critical analysis to bear on the subject.

We exist in a naturally radioactive environment: the rocks and mountains, the sun in particular, produce a “background” level. Average exposure to “background” ionizing radiation worldwide is measured at 2.4 millisievert (mSv) a year. About half of this is from radon gas and its decay products.

However, human activities in the past century have greatly increased our exposure to ionizing radiation, through atomic weapons development, testing and use, as well as uranium-mining and nuclear electricity generation. The ongoing atmospheric fallout from the nuclear weapons testing in the 50s and 60s adds an average extra dose to us all of 0.02mSv per year.


These doses are estimated to have already resulted in 430,000 additional fatal cancers worldwide by the year 2000, and a total of 2.4 million extra cancer deaths long-term.

Unfortunately there is no level of radiation exposure below which we are at zero risk: even low-level medical exposures such as chest X-rays (0.04mSv per test) carry a quantifiable risk of harm. While high doses of ionizing radiation will cause greater health damage, even low doses are associated with adverse environmental and human consequences.

Using the “linear no-threshold” risk model, the 2005 US National Academy of Sciences Committee on the Biological Effects of Ionizing Radiation (BEIR VII) estimated:

  • over a lifetime, a dose of 1mSv creates an excess risk of cancer of approximately 1 in 10,000. Higher doses are associated with proportionately higher risk, for example a dose of 100mSv would cause 1 in 100 people to develop cancer;
  • approximately 1 individual in 100 persons would be expected to develop cancer from a lifetime (70 years) exposure just to background x and gamma rays (excluding radon and other high LET radiations)

It should be noted that while these are average risks, the risks in vulnerable groups of the population may be considerably higher. BEIR VII assessed women as having about twice the radiation risk for solid cancer incidence as men, and 38 per cent higher cancer mortality risk than men.

Children are at even greater risk - radiation during infancy for boys results in three to four times the cancer risk as between 20 to 50 years of age, and female infants have double the risk of boys.


Ionizing radiation causes damage to the DNA in living cells. Atoms and molecules become ionized or excited, which can produce free radicals, break chemical bonds, produce new chemical bonds and cross-linkage between macromolecules and damage molecules that regulate vital cell processes such as DNA, RNA and proteins.

In recent years biologists have identified specific radiation-induced damage at the molecular level to nucleotide sequences on chromosomal DNA, including double-strand breaks, large deletions and sister chromatid exchange.

The cell can repair certain levels of damage in its chromosomal DNA: at low doses cellular damage is usually repaired. However, faulty repairs may lead to cell death or to proliferation of abnormal cells which form a cancer.

At higher levels, cell death results. At extremely high doses, cells cannot be replaced quickly enough, and tissues fail to function; this can result in massive cell death, organ (particularly bone marrow and gut) damage and death to the individual.

Radiation effects are often categorised by when they appear.

The prompt effects include radiation sickness and radiation burns. High doses delivered to the whole body within short periods of time can produce effects such as blood component changes, fatigue, diarrhoea, nausea and death. These effects will develop within hours, days or weeks, depending on the size of the dose. The larger the dose, the sooner a given effect will occur.

When radiation effects are delayed, DNA abnormalities are passed on to subsequent generations of cells, where the abnormal coding can lead to tissue abnormalities, including cancers.

Cancer development is a multistage process, and is similar for radiation-associated cancers as for spontaneous cancers or those associated with exposure to other carcinogens.

Low dose radiation appears to act principally on the early stages of cancer initiation, whereas for higher doses, effects on later stages of cancer promotion and progression are also likely. Genetic disorders associated with deficiencies in the ability to repair DNA damage and in tumour-suppressor type genes (which normally suppress cancer development) increase the radiation cancer risk.

Mutational events at key points such as “proto-oncogene” or “suppressor gene” sites provide a credible mechanism for radiation-induced malignant (cancerous) transformation.

Such cancers will take many cell generations to develop, so it may be several decades before they are detected.

The delay enables polluters to avoid responsibility for the disease-promoting properties of radiation. This avoidance is amplified by the fact that leukemia and other cancers induced by radiation are indistinguishable from those that result from other causes.

Ionising radiation is also responsible for serious reproductive effects through prenatal exposure. Rapidly proliferating and differentiating tissues are most sensitive to radiation damage, so radiation exposure can produce developmental problems, particularly in the developing brain, when the fetus is exposed in the womb.

The developmental conditions most commonly associated with prenatal radiation exposure include low birth weight, microcephaly, mental retardation, and other neurological problems.

Long-term, inter-generational genetic effects are also possible if the damage to the DNA code occurs in a reproductive cell (egg or sperm) whereby the coding error may be passed on to offspring … resulting potentially in birth defects and cancers in the children.

While many plant and animal experiments leave no doubt that radiation exposure can alter genetic material and cause disease, and human data also show DNA and chromosomal damage associated with exposure to ionizing radiation, a resultant effect on genetic diseases has not yet been observed in the case of the Hiroshima and Nagasaki survivors.

This does not mean that there is no such effect in humans. It may be that there were genetic abnormalities produced that were incompatible with life and those pregnancies therefore ended in miscarriage. It may also be that an increased rate of genetic abnormalities will be found in future generations, that is, the changes will skip one or more generations. Radiation-induced genetic damage is likely to manifest mainly as multi-system developmental abnormalities.

Evidence has emerged recently that the cell may also exhibit the phenomenon of “genomic instability”, where the progeny of an irradiated cell may unexpectedly become highly susceptible to general mutation and damage is detected only after several cell divisions. This may also occur in the progeny of cells close to the cell which is traversed by the radiation track but which themselves are not directly hit (“bystander effect”).

This phenomenon has been reproduced several times in laboratory studies of human cells but has not been confirmed in living humans. Such studies would necessarily need to be extraordinarily long. However if the theory of induced genetic instability is correct, then the human gene pool could be permanently altered.

Radiation health authorities use scientific modelling to calculate and set “permissible limits” for ionizing radiation exposure. As the scientific techniques have become more sophisticated, the recommended exposures for the public and the workforce have steadily been reduced: levels once regarded as “safe” are now known to be associated with cancers, bone marrow malignancies and genetic effects.

The dose limits recommended in 1991 by the International Commission on Radiological Protection (ICRP) which are most widely used internationally are more than 12 times lower that those recommended in the early 1950s at the time of the first British nuclear test explosions in Australia.

The growing scientific literature refining our understanding of the pathogenic properties of ionising radiation has dramatically increased pressure on the nuclear industry to reduce radiation exposures.

However, in their rush to give the thumbs-up to nukes, the Prime Minister’s team of “experts”, led by former Telstra chief and ex-nuclear physicist Ziggy Switkowski, make light of the health burden attributable to the nuclear industry.

They are silent on the recent study published in the British Medical Journal which revealed that a cumulative exposure for adult workers in the nuclear industry of 100mSv - the current recommended five-year occupational dose limit - would lead to a 10 per cent increase in mortality from all cancers, and a 19 per cent increased mortality from leukemia (of types other than chronic lymphatic leukemia).

They are silent on multiple reported and controversial clusters of childhood cancers and congenital malformations in the vicinity of nuclear reactors and other nuclear facilities.

They frequently assert a record of “good management” in the Australian nuclear industry to date: a clear misrepresentation in view of hundreds of instances of mismanagement (leaks, spills, contamination, regulatory breaches) at Ranger, Olympic Dam and Beverly and the total failure of either industry or regulators to monitor health impacts in local populations despite known distribution of radio-toxins into habitat and food chain.

The Switkowski Report does not provide either “a factual base” or “an analytical framework” for discussion: it gives a whitewash to a complex and controversial subject. Not only is it likely to exacerbate Australia’s greenhouse emissions by vociferously promoting the nuclear non-solution, but it endangers Australians long-term by threatening to expand an industry whose toxic legacy will continue for many generations.

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About the Author

Dr Bill Williams is a GP in rural Victoria. He is the President of the Medical Association of the Prevention of War, a Board Member of the International Campaign to Abolish Nuclear Weapons, and International Councilor of International Physicians for Prevention of Nuclear War.

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