See also:
- Radiation and Childhood Cancer, detailed 2020 report by radiation biologist Dr. Ian Fairlie
- Medical Association for Prevention of War: mapw.org.au/nuclear-chain/radiation
- Dr Peter Karamoskos, ‘Nuclear Power and Public Health‘
- Radiation harm deniers? Pro-nuclear environmentalists and the Chernobyl death toll
- The Banana Equivalent Dose of catastrophic nuclear accidents
- Dr Bill Williams, 2014, ‘Radiation and Health‘
- Dr John Gofman provides a useful rebuttal of pro-nuclear arguments concerning radiation and health
RADIATION AND HEALTH
Summary — Friends of the Earth Australia
The weight of scientific opinion holds that there is no threshold below which ionising radiation poses no risk of inducing fatal cancers.
Radiation protection agencies establish dose limits for radiation exposure from nuclear facilities but there is no pretence (from radiation protection agencies, at least) that radiation doses below these levels are without risk.
Moreover, as scientific understanding of the effects of ionising radiation has advanced, permitted dose limits have been dramatically reduced. For workers, the permitted dose has decreased by a factor of 25:
* 500 millisieverts (mSv) p.a. in 1934
* 150 mSv in 1950
* 50 mSv in 1956
* 20 mSv (averaged over five years) in 1991.
In 2009 the International Commission on Radiological Protection concluded that radon gas delivers almost twice the radiation dose to humans as originally thought. Previous dose estimates to miners need to be approximately doubled to accurately reflect the lung cancer hazard.
In Australia, the maximum permitted dose is 1 mSv for members of the public (in addition to background radiation which is typically of the order of 2 mSv p.a.)
Linear no-threshold risk model
Radiation protection agencies around the world, including the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA), all base regulations on the linear no-threshold model which assumes that there is no threshold below which radiation exposure is safe.
Uncertainties will always persist because of methodological difficulties. In circumstances where people are exposed to low-level radiation, epidemiological studies are unlikely to be able to demonstrate increased cancer rates because of the ‘statistical noise’ in the form of widespread cancer incidence from many causes, as well as other methodological difficulties. A report by the US Committee on the Biological Effects of Ionising Radiation (BEIR 2005) illustrates the point − it estimated that one out of 100 people exposed to 100 mSv of radiation over a lifetime would probably develop cancer as a result of that exposure, but that 42 cancers can be expected in the same group from causes other than radiation exposure.
The methodological difficulties are discussed in a paper by Dr Sue Wareham (briefing paper #20, www.energyscience.org.au):
“Firstly, health effects such as cancer due to radiation exposure often take decades to develop. Secondly, cancers due to radiation exposure are indistinguishable from any other cancer. Thirdly, radioisotopes can travel great distances. Therefore epidemiological studies investigating the effects of a particular radiation exposure are necessarily very long, they may involve many countries if not continents, and they are extraordinarily complex.
“Add to this the fact that cancer is a common disease in any event, and the result is that a small percentage increase in cancer rates due to radiation exposure can readily be overlooked, even when the absolute number of cancers caused by radiation exposure may be very large.
“A further source of misleading research results is the mixing, inadvertently or knowingly, of data for populations exposed to quite different levels of radiation, for example after a nuclear accident. The results for heavily exposed populations may then be ‘diluted’ by results for much less exposed populations and the results overall will appear reassuringly low.”
Committee on the Biological Effects of Ionising Radiation
Notwithstanding the methodological problems, there is growing scientific confidence in the linear no-threshold model. An important study was the 2005 report of the Committee on the Biological Effects of Ionising Radiation of the US National Academy of Sciences (BEIR 2005). The BEIR report comprehensively reviewed available data and supports the linear no-threshold risk model.
The BEIR Committee states:
“The Committee judges that the balance of evidence from epidemiologic, animal and mechanistic studies tend to favor a simple proportionate relationship at low doses between radiation dose and cancer risk.”
“… the risk of cancer proceeds in a linear fashion at lower doses without a threshold and … the smallest dose has the potential to cause a small increase in risk to humans.”
Richard Monson, Chair of the BEIR Committee and professor of epidemiology at the Harvard School of Public Health, said: “The scientific research base shows that there is no threshold of exposure below which low levels of ionizing radiation can be demonstrated to be harmless or beneficial. The health risks − particularly the development of solid cancers in organs − rise proportionally with exposure. At low doses of radiation, the risk of inducing solid cancers is very small. As the overall lifetime exposure increases, so does the risk.”
The 2005 BEIR report noted that uncertainty remains because of the unavoidable methodological difficulties: “It should be noted however, that even with the increased sensitivity the combined analyses are compatible with a range of possibilities, from a reduction of risk at low doses to risks twice those upon which current radiation protection recommendations are based.”
The BEIR Committee explicitly rejected claims that ionising radiation can be beneficial to health: “The assumption that any stimulatory hormetic effects from low doses of ionizing radiation will have a significant health benefit to humans that exceeds potential detrimental effects from the radiation exposure is unwarranted.”
Other scientists and scientific bodies have reached similar conclusions. A 2010 report by the United Nations Scientific Committee on the Effects of Atomic Radiation states that “the current balance of available evidence tends to favour a non-threshold response for the mutational component of radiation-associated cancer induction at low doses and low dose rates.”
Likewise, a study published in the Proceedings of the National Academy of Sciences (US) in 2003 concluded that: “Given that it is supported by experimentally grounded, quantifiable, biophysical arguments, a linear extrapolation of cancer risks from intermediate to very low doses currently appears to be the most appropriate methodology.”
And to give one more example (there are many), the OECD’s Nuclear Energy Agency states: “There is a threshold level of radiation exposure (or dose) below which no acute damage is observed. However, there is now a substantial body of evidence which shows that cancers can be caused by radiation even at dose levels that are below this threshold. ” (1997, ‘Radiation in Perspective: Applications, Risks and Protection’)
Misinformation arising from methodological problems
The difficulty of demonstrating health impacts from low-level radiation exposure is used by nuclear proponents as the basis for an endless stream of self-serving, disingenuous and scientifically-indefensible statements.
The industry-funded Uranium Information Centre (UIC) ignored predicted deaths from low-level radiation to claim that nuclear power is far safer than alternative energy sources including hydro. Yet the United Nations Scientific Committee on the Effects of Atomic Radiation estimated the collective effective dose to the world population over a 50-year period of operation of nuclear power reactors and associated nuclear facilities to be two million person-Sieverts. Applying the standard risk estimate to that level of radiation exposure gives a total of 80,000 fatal cancers. Of course, applying risk estimates (with their uncertainties) to dose estimates (with their margin of error) is less than precise. But the nuclear industry’s solution − to pretend that its emissions have no impact whatsoever − is dishonest.
To give one further example, the UIC states: “According to authoritative UN figures, the Chernobyl death toll is 56 (31 workers at the time, more since and 9 from thyroid cancer).” However, detailed UN reports in 2005-06 estimated 9,000 cancer deaths due to Chernobyl among the people who worked on the clean-up operations, evacuees and residents of the highly and lower-contaminated regions in Belarus, the Russian Federation and Ukraine. Other, credible scientific studies (listed here) estimate a long-term cancer death toll across Europe ranging from 16,000 to 93,000. Using a standard risk estimate (0.05 cancer deaths per person-Sievert of low-dose exposure to ionising radiation) and the International Atomic Energy Agency’s estimate of total exposure (600,000 person-Sieverts) gives an estimated 30,000 cancer deaths from Chernobyl.
Uranium mining and cancer
Uranium mine workers are exposed to radiation from the ore itself and from the inhalation of radon gas. The waste ore and tailings from uranium mining pose a public health hazard well into the future.
There is a well established link between uranium mining and lung cancer. The BEIR VI report reviewed eleven studies of 60,000 underground uranium miners. It reported 2,600 deaths from lung cancer, eight of which were uranium mines in Europe, North America, Asia and Australia. The report found an increasing frequency of lung cancer in miners. This was directly proportional to the cumulative amount of radon the miners had been exposed to.
In addition to exposure to radon gas, uranium miners are also exposed to gamma radiation directly from the radioactive ore. At the Olympic Dam underground uranium and copper mine, the total annual dose per miner is approximately 6 mSv, of which 2−4 mSv are due to radon gas (allowing for the new ICRP risk estimate for radon) and the balance due to gamma radiation. Workers at the smelter at the Olympic Dam mine receive annual doses that may exceed 12mSv.
Toro Energy promotes dangerous radiation junk science
In May, 45 medical doctors working in Australia released a statement calling on would-be uranium miner Toro Energy to stop promoting the dangerous and scientifically-indefensible claim that low-level radiation is beneficial to human health. Not a single doctor or radiation expert spoke up in defence of Toro Energy.
In a media interview, Toro Energy claimed that “we’ve actually supported different views, scientific views, about the health effects of radiation” and that Doug Boreham (a radiation junk scientist) “is not the only scientist that we support or have supported in the past in terms of sponsorship to conferences”. However there is no evidence for those claims and Toro Energy ignored repeated requests to supply evidence − perhaps the company was simply lying to cover up its promotion of dangerous radiation junk science.
Important 2021 US report
Is there a threshold below which exposure to ionising radiation is harmless? Unfortunately, no. The US Nuclear Regulatory Commission (NRC) noted in a 2021 report:
“Convincing evidence has not yet demonstrated the existence of a threshold below which there would be no stochastic effects from exposure to low radiation doses. As such, the NRC’s view is that the LNT model continues to provide a sound basis for a conservative radiation protection regulatory framework that protects both the public and occupational workers.”
(LNT is linear no-threshold … risks decline as dose declines and there is no threshold below which exposure is risk-free.)
The NRC further notes that “authoritative scientific advisory bodies” such as the National Academy of Sciences, National Council on Radiation Protection and Measurements, International Commission on Radiological Protection and the International Atomic Energy Agency “support the continued use of the LNT model.”
The 2021 NRC report further states:
“In addition to the findings of the national and international authoritative scientific advisory bodies, three Federal agencies provided comments on the petitions and supported the continued use of the LNT model as the basis for the NRC’s radiation protection program. The three agencies are the
National Cancer Institute (NCI), National Institutes of Health, Department of Health and Human Services;
National Institute for Occupational Safety and Health (NIOSH), Centers for Disease Control and Prevention, Department of Health and Human Services;
and the Radiation Protection Division, Office of Air and Radiation, Environmental Protection Agency (EPA).
Furthermore, the NRC’s Advisory Committee on the Medical Uses of Isotopes (ACMUI) recommends that the NRC continue to rely upon the LNT model.”
See the NRC report at: https://www.regulations.gov/document/NRC-2015-0057-0671
Risk of cancer death after exposure to low-dose ionizing radiation underestimated, suggests nuclear industry study
August 16, 2023
Prolonged exposure to low-dose ionizing radiation is associated with a higher risk of death from cancer than previously thought, suggests research tracking the deaths of workers in the nuclear industry, published in The BMJ.
The findings should inform current rules on workplace protection from low-dose radiation, say the researchers.
To date, estimates of the effects of radiation on the risk of dying from cancer have been based primarily on studies of survivors of atomic bombs dropped on Japan at the end of the Second World War.
These estimates are used to set the level of protection required for workers regularly exposed to much lower doses of radiation in the nuclear industry and other sectors such as health care.
But the latest data from the International Nuclear Workers Study (INWORKS) suggest that risk estimates, based on the acute exposures among atomic bomb survivors to an extremely high dose of radiation, may underestimate the cancer risks from exposure to much lower doses of ionizing radiation delivered over a prolonged period in the workplace.
The researchers therefore tracked and analyzed deaths among 309,932 workers in the nuclear industry in the UK, France, and the US (INWORKS) for whom individual monitoring data for external exposure to ionizing radiation were available.
During a monitoring period spanning 1944 to 2016, 103,553 workers died: 28,089 of these deaths were due to solid cancers, which include most cancers other than leukemia.
The researchers then used this information to estimate the risk of death from solid cancers based on workers’ exposure to radiation 10 years previously.
They estimated that this risk increased by 52% for every unit of radiation (Gray; Gy) workers had absorbed. A dose of one Gray is equivalent to a unit of one Joule of energy deposited in a kilogram of a substance.
But when the analysis was restricted to workers who had been exposed to the lowest cumulative doses of radiation (0-100 mGy), this approximately doubled the risk of death from solid cancers per unit Gy absorbed.
Similarly, restricting the analysis only to workers hired in more recent years when estimates of occupational external penetrating radiation dose were more accurate also increased the risk of death from solid cancer per unit Gy absorbed.
Excluding deaths from cancers of the lung and lung cavity, which might be linked to smoking or occupational exposure to asbestos, had little effect on the strength of the association.
The researchers acknowledge some limitations to their findings, including that exposures for workers employed in the early years of the nuclear industry may have been poorly estimated, despite their efforts to account for subsequent improvements in dosimeter technology—a device for measuring exposure to radiation.
They also point out that the separate analysis of deaths restricted to workers hired in more recent years found an even higher risk of death from solid cancer per unit Gy absorbed, meaning that the increased risk observed in the full cohort wasn’t driven by workers employed in the earliest years of the industry. There were also no individual level data on several potentially influential factors, including smoking.
“People often assume that low dose rate exposures pose less carcinogenic hazard than the high dose rate exposures experienced by the Japanese atomic bomb survivors,” write the researchers. “Our study does not find evidence of reduced risk per unit dose for solid cancer among workers typically exposed to radiation at low dose rates.”
They hope that organizations such as the International Commission on Radiological Protection will use their results to inform their assessment of the risks of low dose, and low dose rate, radiation and ultimately in an update of the system of radiological protection.
More information: Cancer mortality after low dose exposure to ionising radiation in workers in France, the United Kingdom, and the United States (INWORKS): cohort study, The BMJ (2023). DOI: 10.1136/bmj-2022-074520
Journal information: British Medical Journal (BMJ)
Provided by British Medical Journal
Explore further: Low-dose radiation linked to increased lifetime risk of heart disease
Ionising radiation and cardiovascular diseases
Ionising radiation and cardiovascular disease: systematic review and meta-analysis. An important new study in the BMJ – a meta-analysis of 93 health studies. The authors conclude, inter alia, “Our findings suggest that radiation detriment might have been significantly underestimated, implying that radiation protection and optimisation at low doses should be rethought.” And also “This finding has considerable implications for the system of radiological protection, assuming that the extrapolation is permissible, even, for example, over the restricted dose range 0-0.5 Gy. This added risk would nearly double the low dose detriment.”
BMJ 8th March 2023, https://www.bmj.com/content/380/bmj-2022-072924
Editorial: Little and colleagues report the results of a large meta-analysis of 93 studies evaluating associations between a range of cardiovascular diseases and exposure to radiation in various settings (mostly radiotherapy and occupational exposures, but also diagnostic radiology and environmental exposures). The authors found robust evidence for a dose dependent increase in cardiovascular risks across a broad range of radiation doses. Key findings included a higher relative risk per dose unit at lower dose ranges (<0.1 Gy), and also for lower dose rates (protracted exposures over hours to years). The studies included in the meta-analysis were published mainly during the past decade. This new meta-analysis strengthens the evidence linking low dose radiation to risk of circulatory diseases and these risks should now be carefully considered in protection against radiation in medicine and elsewhere.
BMJ 8th March 2023, https://www.bmj.com/content/380/bmj-2022-074589
See also the discussion by radiation biologist Dr Ian Fairlie:
A 100 mSv threshold for radiation effects?
One of the lies peddled by nuclear apologists – including James Hansen – is that radiation doses below 100 millisieverts are harmless. This paper by Dr Ian Fairlie gives the lie to those lies …
A 100 mSv threshold for radiation effects?
November 27, 2012
In recent years, some scientists have promoted the view that there are no observable effects from radiation below 100 mSv, usually in their criticisms of the Linear No Threshold theory. However, many studies show radiation effects well below 100 mSv.
Read on at: http://www.ianfairlie.org/news/a-100-msv-threshold-for-radiation-effects/
Current research evidence about health problems from radiation
Dr Margaret Beavis, May 2014
This plain language fact sheet outlines current research evidence about health problems from radiation
Executive Summary:
- Even at low doses of radiation there is clear evidence of increased risk of cancer and cardiovascular disease. There is no safe lower dose.
- The risk of increased cancers has been clearly shown in studies with very large numbers of people: Workers in the nuclear industry, children having CT Scans, survivors of Nagasaki and Hiroshima, mine workers and householders exposed to raised levels of radon gas and in unborn children when their mothers had had abdominal X-rays.
- The risk of death from cardiovascular diseases is similar to that of dying of cancer, and the role of radiation causing other types of illness is currently being researched. As a result the overall excess risk of dying from exposure to low doses of radiation may be twice (or more) than that currently assumed from cancer alone.
The trend in research over the last couple of decades, as each bit of new evidence emerges, is that the risks are greater than previously thought. There is now clear evidence that low dose exposures are harmful, and the greater the exposure the greater the risk.
Full paper:
Aboriginal people near the Ranger uranium mine suffered more stillbirths and cancer. We don’t know why
Rosalie Schultz writing in The Conversation.
The Ranger uranium mine, surrounded by Kakadu National Park in the Northern Territory, operated for 40 years until it closed in 2021. During this time, Aboriginal people in the region experienced stillbirth rates double those of Aboriginal people elsewhere in the Top End, and cancer rates almost 50% higher.
UNSCEAR Summary Report on Effects of Low Doses of Radiation
UN Scientific Committee on the Effects of Atomic Radiation
ScienceDaily, May 23, 2012, www.sciencedaily.com/releases/2012/05/120523170536.htm
Key findings:
• There is strong evidence of “statistically significant” elevations of risk of solid tumours and leukaemia above doses of 100 — 200 milligray (mGy)
• Findings of elevated incidence of circulatory disease in populations irradiated at high doses are raising some concern
• There is “increasing evidence” of radiation exposure leading to increased incidence of cataracts
The Report uses the term ‘low dose’ to mean doses of radiation below 200 mGy — a computed tomography scan delivers about 10 mGy. It consolidates and summarizes findings from its detailed reports on various aspects over the last several years.
The Committee evaluated information in two general classes:
(a) studies of populations irradiated at moderate or high doses (epidemiological studies), such as survivors of the Hiroshima and Nagasaki bombings; and
(b) experimental studies that examine the mechanism by which the biological effect or disease arises, from animal and cultured cell studies
There are many difficulties in attributing observed cases of disease to low dose exposure. (1) There are no specific markers for radiation-induced diseases. (2) A significant passage of time, “years or decades” may elapse between exposure and onset of disease. (3) And diseases associated with radiation also occur spontaneously in an ageing population. This means that epidemiological studies often fail to reveal clear links.
Nevertheless “there is strong epidemiological evidence that exposure of humans to radiation at moderate and high levels can lead to excess incidence of solid tumours in many body organs and of leukaemia.” The report states that “statistically significant elevations in risk are observed at doses of 100 — 200 mGy and above.” (The increased risk of fatal cancer is about 1 per cent at these levels, which are equivalent to between 10 and 20 computed tomography scans). The report notes that younger people are more sensitive.
It also says that experimental studies have hypothesized several responses to radiation exposure that could serve to increase or decrease cancer risks at low doses:
• adaptive response — low doses of radiation may cause cells and tissues to become more resistant to cancer development
• effects on immune systems — which recognize and destroy abnormal cells, could influence the likelihood of cancer development
• genomic instability — radiation can produce changes that have long lasting and transmissible effects on the stability of cellular DNA
• bystander effects — radiation may trigger the transfer of signals from damaged cells to undamaged neighbours.
The Committee has reviewed these studies and judges that these processes do not contribute significantly to the interpretation of the epidemiological data.
Unlike the studies on cancer, epidemiological studies have not provided clear evidence of excess heritable effects of radiation exposure in humans, not even from the survivors of the atomic bombings in Japan. Nevertheless these studies provide an upper boundary for the estimate of any associated risk.
Radiation exposure of the developing embryo or foetus above about 100 mGy during specific periods of pregnancy can induce congenital malformations and affect the central nervous system.
There is clear evidence of an increased risk of cardiovascular disease associated with radiation exposure at doses above 1000 to 2000 mGy, Evidence is emerging indicating elevated incidence of non-cancer diseases below these levels. But the Committee’s review could not draw any conclusions about a direct causal relationship between lower levels of irradiation and cardiovascular and other non-cancer diseases, though this is an area of active research.
The Committee also notes that recent studies have suggested that an increased incidence of cataracts may be associated with low-dose radiation exposure.
The Committee will continue to monitor and review new findings in these areas that might contribute to a more complete understanding of the health effects of low-dose radiation exposure and of the mechanisms that explain them.
The mandate of UNSCEAR, established in 1955, is to undertake broad reviews of the sources of ionizing radiation and the effects on human health and the environment. Its assessments provide a scientific foundation for United Nations agencies and governments to formulate standards and programmes for protection against ionizing radiation.
Note: The Summary Report on the effects of low-dose radiation is available at: http://www.unscear.org/unscear/en/publications.html
Childhood Leukemias Near Nuclear Power Stations
Ian Fairlie, 25 July 2014, http://www.ianfairlie.org/news/childhood-leukemias-near-nuclear-power-stations-new-article/
Dr. Ian Fairlie is a radiation biologist who formerly worked as a civil servant on the regulation of radiation risks from nuclear power stations. From 2000 to 2004, he was head of the Secretariat of the UK Government’s CERRIE Committee on internal radiation risks.
In March 2014, my article on increased rates of childhood leukemias near nuclear power plants (NPPs) was published in the Journal of Environmental Radioactivity (JENR). A previous post discussed the making of the article and its high readership: this post describes its content in layman’s terms.
Before we start, some background is necessary to grasp the new report’s significance. Many readers may be unaware that increased childhood leukemias near NPPs have been a contentious issue for several decades. For example, it was a huge issue in the UK in the 1980s and early 1990s leading to several TV programmes, Government Commissions, Government committees, a major international Conference, Government reports, at least two mammoth court cases and probably over a hundred scientific articles. It was refuelled in 1990 by the publication of the famous Gardner report (Gardner et al, 1990) which found a very large increase (7 fold) in child leukemias near the infamous Sellafield nuclear facility in Cumbria.
The issue seems to have subsided in the UK, but it is still hotly debated in most other European countries, especially Germany.
The core issue is that, world-wide, over 60 epidemiological studies have examined cancer incidences in children near nuclear power plants (NPPs): most (>70%) indicate leukemia increases. I can think of no other area of toxicology (eg asbestos, lead, smoking) with so many studies, and with such clear associations as those between NPPs and child leukemias. Yet many nuclear Governments and the nuclear industry refute these findings and continue to resist their implications. It’s similar to the situations with cigarette smoking in the 1960s and with man-made global warming nowadays.
In early 2009, the debate was partly rekindled by the renowned KiKK study (Kaatsch et al, 2008) commissioned by the German Government which found a 60% increase in total cancers and 120% increase in leukemias among children under 5 yrs old living within 5 km of all German NPPs. As a result of these surprising findings, governments in France, Switzerland and the UK hurriedly set up studies near their own NPPs. All found leukemia increases but because their numbers were small the increases lacked “statistical significance”. That is, you couldn’t be 95% sure the findings weren’t chance ones.
This does not mean there were no increases, and indeed if less strict statistical tests had been applied, the results would have been “statistically significant”. But most people are easily bamboozled by statistics including scientists who should know better, and the strict 95% level tests were eagerly grasped by the governments wishing to avoid unwelcome findings. Indeed, many tests nowadays in this area use a 90% level.
In such situations, what you need to do is combine datasets in a meta-study to get larger numbers and thus reach higher levels of statistical significance. The four governments refrained from doing this because they knew what the answer would be, viz, statistically significant increases near almost all NPPs in the 4 countries. So Korblein and Fairlie helped them out by doing it for them (Korblein and Fairlie, 2012), and sure enough there were statistically significant increases near all the NPPs. Here are their findings:
Studies of observed (O) and expected (E) leukemia cases within 5 km of NPPs
| O | E | SIR=O/E | 90% CI | p-value | |
| Germany | 34 | 24.1 | 1.41 | 1.04-1.88 | 0.0328 |
| Great Britain | 20 | 15.4 | 1.30 | 0.86-1.89 | 0.1464 |
| Switzerland | 11 | 7.9a | 1.40 | 0.78-2.31 | 0.1711 |
| Franceb | 14 | 10.2 | 1.37 | 0.83-2.15 | 0.1506 |
| Pooled data | 79 | 57.5 | 1.37 | 1.13-1.66 | 0.0042 |
a derived from data in Spycher et al. (2011).
b acute leukemia cases
This table reveals a highly statistically significant 37% increase in childhood leukemias within 5 km of almost all NPPs in the UK, Germany, France and Switzerland. It’s perhaps not surprising that the latter 3 countries have announced nuclear phaseouts and withdrawals. It is only the UK government that remains in denial.
So the matter is now beyond question, ie there’s a very clear association between increased child leukemias and proximity to NPPs. The remaining question is its cause(s).
Most people worry about radioactive emissions and direct radiation from the NPPs, however any theory involving radiation has a major difficulty to overcome, and that is how to account for the large (~10,000 fold) discrepancy between official dose estimates from NPP emissions and the clearly-observed increased risks.
My explanation does involve radiation. It stems from KiKK’s prinicipal finding that the increased incidences of infant and child leukemias were closely associated with proximity to the NPP chimneys. It also stems from KiKK’s observation that the increased solid cancers were mostly “embryonal”, ie babies were born either with solid cancers or with pre-cancerous tissues which, after birth, developed into full-blown tumours: this actually happens with leukemia as well.
My explanation has five main elements. First, the cancer increases may be due to radiation exposures from NPP emissions to air. Second, large annual spikes in NPP emissions may result in increased dose rates to populations within 5 km of NPPs. Third, the observed cancers may arise in utero in pregnant women. Fourth, both the doses and their risks to embryos and to fetuses may be greater than current estimates. And fifth, pre-natal blood-forming cells in bone marrow may be unusually radiosensitive. Together these five factors offer a possible explanation for the discrepancy between estimated radiation doses from NPP releases and the risks observed by the KIKK study. These factors are discussed in considerable detail in the full article.
My article in fact shows that the current discrepancy can be explained. The leukemia increases observed by KiKK and by many other studies may arise in utero as a result of embryonal/fetal exposures to incorporated radionuclides from NPP radioactive emissions. Very large emission spikes from NPPs might produce a pre-leukemic clone, and after birth a second radiation hit might transform a few of these clones into full-blown leukemia cells. The affected babies are born pre-leukemic (which is invisible) and the full leukemias are only diagnosed within the first few years after birth.
To date, no letters to the editor have been received pointing out errors or omissions in this article.
REFERENCES
Bithell JF, M F G Murphy, C A Stiller, E Toumpakari, T Vincent and R Wakeford. (2013) Leukaemia in young children in the vicinity of British nuclear power plants: a case–control study. Br J Cancer. advance online publication, September 12, 2013; doi:10.1038/bjc.2013.560.
Bunch KJ, T J Vincent1, R J Black, M S Pearce, R J Q McNally, P A McKinney, L Parker, A W Craft and M F G Murphy (2014) Updated investigations of cancer excesses in individuals born or resident in the vicinity of Sellafield and Dounreay. British Journal of Cancer (2014), 1–10 | doi: 10.1038/bjc.2014.357
Fairlie I (2013) A hypothesis to explain childhood cancers near nuclear power plants. Journal of Environmental Radioactivity 133 (2014) 10e17
Gardner MJ, Snee MP; Hall AJ; Powell CA; Downes S; Terrell JD (1990) Results of case-control study of leukaemia and lymphoma among young people near Sellafield nuclear plant in West Cumbria. BMJ. 1990;300:423–429.
Kaatsch P, Spix C, Schulze-Rath R, Schmiedel S, Blettner M. (2008) Leukaemia in young children living in the vicinity of German nuclear power plants. Int J Cancer; 122: 721-726.
Körblein A and Fairlie I (2012) French Geocap study confirms increased leukemia risks in young children near nuclear power plants. Int J Cancer 131: 2970–2971.
Spycher BD, Feller M, Zwahlen M, Röösli M, von der Weid NX, Hengartner H, Egger M, Kuehni CE. Childhood cancer and nuclear power plants in Switzerland: A census based cohort study. International Journal of Epidemiology (2011) doi:10.1093/ije/DYR115. http://ije.oxfordjournals.org/content/early/2011/07/11/ije.dyr115.full.pdf+html
Radioactive spikes from nuclear plants – a likely cause of childhood leukemia
Dr Ian Fairlie, 29 Sept 2014,
www.theecologist.org/News/news_analysis/2574389/radioactive_spikes_from_nuclear_plants_a_likely_cause_of_childhood_leukemia.html
When nuclear reactors are refueled, a 12-hour spike in radioactive emissions exposes local people to levels of radioactivity up to 500 times greater than during normal operation, writes Ian Fairlie. The spikes may explain infant leukemia increases near nuclear plants – but operators provide no warnings and take no measures to reduce exposures.
Nuclear operators should inform local people when they intend to open up their reactors, and they should only do so at night-time and when the winds are blowing out to sea.
On 23rd August, The Ecologist published very clear evidence of increased cancers among children living near nuclear power stations around the world, including the UK.
The story sparked much interest on social media sites, and perhaps more importantly, the article’s scientific basis (published in the academic peer-reviewed scientific journal the Journal of Environmental Radioactivity) was downloaded over 500 times by scientists.
Given this level of interest and the fact that the UK government is still pressing ahead with its bizarre plans for more nuclear stations, we return to this matter − and examine in more detail an important aspect which has hitherto received little attention: massive spikes in radioactive emissions from nuclear reactors.
Refueling releases a huge radioactive emissions plume
Operating nuclear power plants (NPPs) contain large volumes of radioactive gases at high pressures and temperatures. When their reactors are depressurised and opened to refuel every 12-18 months, these gases escape creating a spiked emission and a large radioactive plume downwind of the station lasting for 12 hours or so.
However the emissions and plumes are invisible, and no advance warning is ever given of these spikes. The public is effectively kept in the dark about them, despite their possible health dangers.
For years, I had tried to obtain data on these spikes, but ever since the start of the nuclear era back in 1956, governments and nuclear power operators have been extremely loath to divulge this data.
Only annual emissions are made public and these effectively disguise the spikes. No data is ever given on daily or hourly emissions.
Is this important? Yes: these spikes could help answer a question which has puzzled the public and radiation protection agencies for decades – the reason for the large increases in childhood leukemias near NPPs all over the world.
Governments have insisted that these increased leukemias could not be caused by radioactive emissions from NPPs as their estimated radiation doses were ~1,000 times too low. But these don’t take the time patterns of radioactive emissions into account, and so are riddled with uncertainties.
500 times more radiation released than during normal operation
This situation lasted until September 2011, when the International Physicians for the Prevention of Nuclear War (IPPNW) in Germany released a press notice. For the very first time anywhere in the world, half-hourly data on releases of radioactive noble gases from an NPP were made public.
This is shown in the chart for 7 days in September 2011. These data were from Gundremmingen NPP − in Bavaria, Southern Germany.
The chart showed that the normal emission concentration (of noble gases) during the rest of the year was about 3 kBq/m³ (see squiggly line along the bottom on September 19 and 20) , but during refuelling on September 22 and 23 this sharply increased to ~700 kBq/m³ with a peak of 1,470 kBq/m³: in other words, a spike.
Primarily, the spike includes radioactive noble gases and hydrogen-3 (tritium) and smaller amounts of carbon-14 and iodine-131.
This data shows that NPPs emit much larger amounts of radioactive noble gases during refuelling than during normal operation in the rest of the year.
From the new data, Nuremberg physicist and statistician, Dr Alfred Körblein, has estimated that, at its maximum value, the concentration of noble gas emissions during refueling was 500 times greater than during normal reactor operation. He also has estimated that about two thirds of the NPP’s annual emissions occur during refuelling.
20-100 times dose increases to local populations
In May 2011 in Germany, Green MPs entered the Bavarian State Parliament (Landtag) for the first time where they formed the Government in coalition with the German Socialist Party (SPD).
After several requests, the new Bavarian Government insisted that the state nuclear regulator release non-averaged data on emissions. The highly reluctant nuclear regulator was compelled to respond.
In other words, the Green MPs obtained the data because they had the political power to force its release: there is a lesson here for British environmentalists.
So could these spikes help explain leukemia increases near nuclear plants? Yes they could. People living near nuclear power stations and downwind from them will be exposed to high doses of radiation during these emissions spikes – estimated to be 20-100 times higher than from the tiny releases during the rest of the year.
In 2011, the UK National Dose Assessment Working Group published guidance on ‘Short Term Releases to the Atmosphere‘. This stated that “…doses from the assessment of a single realistic short-term release are a factor of about 20 greater than doses from the continuous release assessment.”
An older German study (Hinrichsen, 2001) indicated that these doses could be 100 times greater. (Hinrichsen K (2001) Critical appraisal of the meteorological basis used in General Administrative Regulations (re dispersion coefficients for airborne releases of NPPs) See Annex D page 9: Radiation Biological Opinion (in German).
A dramatic increase in individual doses
Some scientists think that the time pattern is unimportant and only the population dose is relevant, but this turns out not to be the case. The reason is partly related to the duration of the release, as short releases produce very narrow plumes (plume widths vary non-linearly as a fractional power of the duration).
The result is that individual doses increase dramatically per Bq emitted. Another reason is that spikes result in high concentrations of organically bound tritium and carbon-14 in environmental materials and humans which have longer retentions and thus higher doses.
The precise amount will depend on many factors, including source term, proximity to the reactor, wind speed, wind direction, and the diets and habits of local people.
Even before the new data, official sources didn’t have a good handle on these doses to local people. Official estimates of radiation doses from NPPs already contain many uncertainties, that is, they could be many times larger than admitted.
This was shown in the 2004 CERRIE Report, a UK Government Committee which showed that dose estimates from environmental releases depended on many computer models and the assumptions they contained. The new information on radioactive spikes adds to these uncertainties.
Therefore higher doses from emission spikes could go a long way to explaining the increased incidences of child leukemias near NPPs shown by the KiKK findings.
‘Especially at risk are unborn children’
IPPNW Germany warned of the probable health impacts of such large emission spikes. Dr Reinhold Thiel, a member of the German IPPNW Board said:
“Especially at risk are unborn children. When reactors are open and releasing gases, pregnant women can incorporate much higher concentrations of radionuclides than at other times, mainly via respiration. Radioactive isotopes inhaled by the mother can reach the unborn child via blood with the result that the embryo/ fetus is contaminated by radioactive isotopes.
“This contamination could affect blood-forming cells in the bone marrow resulting later in leukemia. This provides a plausible explanation for the findings of the KiKK study published in 2008 that under-fives living near NPPs are considerably more at risk of cancer, particularly leukemia, than children living further away.”
In the light of the German data, it is recommended half-hourly emissions data from all UK reactors should be disclosed and that the issue of childhood cancer increases near NPPs be re-examined by the Government.
Nuclear operators should inform local people when they intend to open up their reactors, and they should only do so at night-time (when most people are indoors) and when the winds are blowing out to sea.
Dr Ian Fairlie is an independent consultant on radioactivity in the environment. He has a degree in radiation biology from Bart’s Hospital in London and his doctoral studies at Imperial College in London and Princeton University in the US concerned the radiological hazards of nuclear fuel reprocessing.
Ian was formerly a DEFRA civil servant on radiation risks from nuclear power stations. From 2000 to 2004, he was head of the Secretariat to the UK Government’s CERRIE Committee on internal radiation risks. Since retiring from Government service, he has acted as consultant to the European Parliament, local and regional governments, environmental NGOs, and private individuals.
See also Ian Fairlie’s blog.
Science says …
The National Council on Radiation Protection says, “every increment of radiation exposure produces an incremental increase in the risk of cancer.”
The US Environmental Protection Agency says, “any exposure to radiation poses some risk, i.e. there is no level below which we can say an exposure poses no risk.”
The US Department of Energy says about “low levels of radiation” that “… the major effect is a very slight increase in cancer risk.”
The US Nuclear Regulatory Commission says, “any amount of radiation may pose some risk for causing cancer … any increase in dose, no matter how small, results in an incremental increase in risk.”
The National Academy of Sciences, in its “Biological Effects of Ionizing Radiation VII,” says, “it is unlikely that a threshold exists for the induction of cancers ….”
Source: http://www.commondreams.org/view/2011/03/23-1
Even Low-Level Radioactivity Is Damaging, Scientists Conclude
University of South Carolina, 13 Nov 2012, ‘Even low-level radioactivity is damaging, scientists conclude. ScienceDaily’, www.sciencedaily.com /releases/2012/11/121113134224.htm
Even the very lowest levels of radiation are harmful to life, scientists have concluded in the Cambridge Philosophical Society’s journal Biological Reviews. Reporting the results of a wide-ranging analysis of 46 peer-reviewed studies published over the past 40 years, researchers from the University of South Carolina and the University of Paris-Sud found that variation in low-level, natural background radiation was found to have small, but highly statistically significant, negative effects on DNA as well as several measures of health.
The review is a meta-analysis of studies of locations around the globe that have very high natural background radiation as a result of the minerals in the ground there, including Ramsar, Iran, Mombasa, Kenya, Lodeve, France, and Yangjiang, China. These, and a few other geographic locations with natural background radiation that greatly exceeds normal amounts, have long drawn scientists intent on understanding the effects of radiation on life. Individual studies by themselves, however, have often only shown small effects on small populations from which conclusive statistical conclusions were difficult to draw.
“When you’re looking at such small effect sizes, the size of the population you need to study is huge,” said co-author Timothy Mousseau, a biologist in the College of Arts and Sciences at the University of South Carolina. “Pooling across multiple studies, in multiple areas, and in a rigorous statistical manner provides a tool to really get at these questions about low-level radiation.”
Mousseau and co-author Anders Møller of the University of Paris-Sud combed the scientific literature, examining more than 5,000 papers involving natural background radiation that were narrowed to 46 for quantitative comparison. The selected studies all examined both a control group and a more highly irradiated population and quantified the size of the radiation levels for each. Each paper also reported test statistics that allowed direct comparison between the studies.
The organisms studied included plants and animals, but had a large preponderance of human subjects. Each study examined one or more possible effects of radiation, such as DNA damage measured in the lab, prevalence of a disease such as Down’s Syndrome, or the sex ratio produced in offspring. For each effect, a statistical algorithm was used to generate a single value, the effect size, which could be compared across all the studies.
The scientists reported significant negative effects in a range of categories, including immunology, physiology, mutation and disease occurrence. The frequency of negative effects was beyond that of random chance.
“There’s been a sentiment in the community that because we don’t see obvious effects in some of these places, or that what we see tends to be small and localized, that maybe there aren’t any negative effects from low levels of radiation,” said Mousseau. “But when you do the meta-analysis, you do see significant negative effects.”
“It also provides evidence that there is no threshold below which there are no effects of radiation,” he added. “A theory that has been batted around a lot over the last couple of decades is the idea that is there a threshold of exposure below which there are no negative consequences. These data provide fairly strong evidence that there is no threshold — radiation effects are measurable as far down as you can go, given the statistical power you have at hand.”
Mousseau hopes their results, which are consistent with the “linear-no-threshold” model for radiation effects, will better inform the debate about exposure risks. “With the levels of contamination that we have seen as a result of nuclear power plants, especially in the past, and even as a result of Chernobyl and Fukushima and related accidents, there’s an attempt in the industry to downplay the doses that the populations are getting, because maybe it’s only one or two times beyond what is thought to be the natural background level,” he said. “But they’re assuming the natural background levels are fine.”
“And the truth is, if we see effects at these low levels, then we have to be thinking differently about how we develop regulations for exposures, and especially intentional exposures to populations, like the emissions from nuclear power plants, medical procedures, and even some x-ray machines at airports.”
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Journal Reference:
Anders P. Møller, Timothy A. Mousseau. The effects of natural variation in background radioactivity on humans, animals and other organisms. Biological Reviews, 2012; DOI: 10.1111/j.1469-185X.2012.00249.x
No safe dose
By Dr Bill Williams, 12 December 2006, www.onlineopinion.com.au/view.asp?article=5249&page=0
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 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.
Dr Bill Williams is a GP in rural Victoria. He is the Vice President of the Medical Association of the Prevention of War and Board Member of the International Campaign to Abolish Nuclear Weapons.
Ionizing radiation, health effects and protective measures
World Health Organisation
Fact sheet No.371, November 2012, http://www.who.int/mediacentre/factsheets/fs371/en/index.html
Ionizing radiation is a type of energy released by atoms in the form of electromagnetic waves or particles.
People are exposed to natural sources of ionizing radiation, such as in soil, water, vegetation, and in human-made sources, such as x-rays and medical devices.
Ionizing radiation has many beneficial applications, including uses in medicine, industry, agriculture and research.
As the use of ionizing radiation increases, so does the potential for health hazards if not properly used or contained.
Acute health effects such as skin burns or acute radiation syndrome can occur when doses of radiation exceed certain levels.
Low doses of ionizing radiation can increase the risk of longer term effects such as cancer.
What is ionizing radiation?
Ionizing radiation is a type of energy released by atoms that travels in the form of electromagnetic waves (gamma or X-rays) or particles (neutrons, beta or alpha). The spontaneous disintegration of atoms is called radioactivity, and the excess energy emitted is a form of ionizing radiation. Unstable elements which disintegrate and emit ionizing radiation are called radionuclides.
All radionuclides are uniquely identified by the type of radiation they emit, the energy of the radiation, and their half-life.
The activity — used as a measure of the amount of a radionuclide present — is expressed in a unit called the becquerel (Bq): one becquerel is one disintegration per second. The half-life is the time required for the activity of a radionuclide to decrease by decay to half of its initial value. The half-life of a radioactive element is the time that it takes for one half of its atoms to disintegrate. This can range from a mere fraction of a second to millions of years (e.g. iodine-131 has a half-life of 8 days while carbon-14 has a half-life of 5730 years).
Radiation sources
People are exposed to natural radiation on a daily basis. Natural radiation comes from many sources including more than 60 naturally-occurring radioactive materials found in soil, water and air. Radon, a naturally-occurring gas, emanates from rock and soil and is the main source of natural radiation. Every day, people inhale and ingest radionuclides from air, food and water.
People are also exposed to natural radiation from cosmic rays, particularly at high altitude. On average, 80% of the annual dose that a person receives of background radiation is due to naturally occurring terrestrial and cosmic radiation sources. Background radiation levels vary due to geological differences. Exposure in certain areas can be more than 200 times higher than the global average.
Human exposure to radiation also comes from human-made sources ranging from nuclear power generation to medical uses of radiation diagnosis or treatment. Today, the most common human-made sources of ionizing radiation are X-ray machines and other medical devices.
Type of exposure
Radiation exposure may be internal or external, and can be acquired through various exposure pathways.
Internal exposure to ionizing radiation occurs when a radionuclide is inhaled, ingested or otherwise enters into the bloodstream (e.g. injection, wounds). Internal exposure stops when the radionuclide is eliminated from the body, either spontaneously (e.g. through excreta) or as a result of a treatment.
External contamination may occur when airborne radioactive material (dust, liquid, aerosols) is deposited on skin or clothes. This type of radioactive material can often be removed from the body by simply washing.
Exposure to ionizing radiation can also result from external irradiation (e.g. medical radiation exposure to X-rays). External irradiation stops when the radiation source is shielded or when the person moves outside the radiation field.
Health effects of ionizing radiation
Radiation damage to tissue and/or organs depends on the dose of radiation received, or the absorbed dose which is expressed in a unit called the gray (Gy). The potential damage from an absorbed dose depends on the type of radiation and the sensitivity of different tissues and organs.
The sievert (Sv) is a unit of radiation weighted dose also called the effective dose. It is a way to measure ionizing radiation in terms of the potential for causing harm. The Sv takes into account the type of radiation and sensitivity of tissues and organs. The Sv is a very large unit so it is more practical to use smaller units such as millisieverts (mSv) or microsieverts (Sv). There are one thousand Sv in one mSv, and one thousand mSv in one Sv. In addition to the amount of radiation (dose), it is often useful to express the rate at which this dose is delivered (dose rate) e.g. Sv/hour or mSv/year.
Beyond certain thresholds, radiation can impair the functioning of tissues and/or organs and can produce acute effects such as skin redness, hair loss, radiation burns, or acute radiation syndrome. These effects are more severe at higher doses and higher dose rates. For instance, the dose threshold for acute radiation syndrome is about 1 Sv (1000 mSv).
If the dose is low or delivered over a long period of time (low dose rate), there is greater likelihood for damaged cells to successfully repair themselves. However, long-term effects may still occur if the cell damage is repaired but incorporates errors, transforming an irradiated cell that still retains its capacity for cell division. This transformation may lead to cancer after years or even decades have passed. Effects of this type will not always occur, but their likelihood is proportional to the radiation dose.
This risk is higher for children and adolescents, as they are significantly more sensitive to radiation exposure than adults.
Epidemiological studies on populations exposed to radiation (for example atomic bomb survivors or radiotherapy patients) showed a significant increase of cancer risk at doses above 100 mSv.
Prenatal exposure to ionizing radiation may induce brain damage in foetuses following an acute dose exceeding 100 mSv between weeks 8-15 of pregnancy and 200 mSv between weeks 16-25 of pregnancy. Before week 8 or after week 25 of pregnancy human studies have not shown radiation risk to fetal brain development. Epidemiological studies indicate that cancer risk after fetal exposure to radiation is similar to the risk after exposure in early childhood.
Radiation exposure in nuclear emergencies
Radioactive material may be released into the environment during an emergency in a nuclear power plant (NPP). The radionuclides of greatest concern to human health are iodine and caesium.
Occupational exposure, either internally or externally, of rescuers, first responders, and NPP workers is likely to occur during the emergency response. It may result in radiation doses high enough to cause acute effects such as skin burns or acute radiation syndrome.
Those living in closer vicinity to a NPP can be externally exposed to radionuclides present in a radioactive cloud or deposited on the ground. They can also be externally contaminated by radioactive particles deposited on skin or clothes. Internal exposure may take place if radionuclides are inhaled, ingested, or enter an open wound.
The general population is not likely to be exposed to doses high enough to cause acute effects, but they may be exposed to low doses which could result in increased risk of long-term effects like cancer. Consumption of contaminated food and/or water contributes to overall radiation exposure.
If radioactive iodine is released into the environment and enters the body through inhalation or ingestion, it will concentrate in the thyroid gland increasing the risk of thyroid cancer. The risk of thyroid cancer is higher in children than adults, particularly those under 5 years, and those whose diets are generally deficient in iodine.
Protective health actions in nuclear emergencies
During nuclear emergencies, public health protective actions may be implemented to limit radiation exposure and associated health risks.
In the early phase of an emergency (within the first few hours/days), urgent protective actions should be implemented to prevent radiation exposure, taking into account projected doses that people may received in the short-term (e.g. effective dose within 2-7 days, thyroid dose within one week). Decisions are based on NPP conditions, amount of radioactivity actually or potentially released into the atmosphere, prevailing meteorological conditions (e.g. wind speed and direction, precipitation), and other factors. Local authorities may announce urgent actions including evacuation, sheltering indoors, and the administration of non-radioactive iodine.
Evacuation is most effective when used as a precautionary action before an airborne release takes place. Sheltering indoors (e.g. homes, schools, and office buildings) can also significantly reduce exposure to the radioactive material released and dispersed.
The administration of non-radioactive iodine can prevent the uptake of radioactive iodine by the thyroid gland. When potassium iodide (KI) pills are taken before or shortly after exposure, they saturate the thyroid gland to reduce the dose and risk of thyroid cancer. KI pills do not protect against external radiation, or against any other radioactive substances apart from radioactive iodine.
Potassium iodide pills should be taken only when instructed by competent authorities. It is important to follow dosage recommendations, especially for children. Pregnant women should take KI pills when instructed by competent authorities to protect their thyroid and the thyroid of the fetus. When instructed, breastfeeding women should also take KI pills to protect themselves, and give KI to the breastfed baby following recommended dosages.
Food, water and agricultural countermeasures may be implemented to reduce radiation exposure during the early phase of an emergency (e.g. restricting consumption of water, and locally produced food and dairy products).
Mental health support to manage acute stress after a nuclear event can speed recovery and prevent long-term consequences such as post-traumatic stress disorder or other persistent mental health disorders. Reactions may be intense and prolonged with profound emotional impact, particularly in children.
As environmental and human monitoring data increase, other protective actions may be implemented, including relocation of people to temporary housing or in some cases, permanent resettlement. These protective actions are implemented taking into account the doses that a population may receive over the long-term (e.g. effective dose during one year). Food and water monitoring programmes should be established to inform longer-term decisions on food restriction, water consumption, and the control of internationally traded foodstuffs.
The recovery phase may last for a considerable period. Cessation of protective measures should be linked to environmental, food and human health monitoring and based on a risk-benefit analysis. Appropriate long-term follow-up programmes should be established to assess public health consequences and the need for any subsequent actions.