The Death Toll from Chernobyl - how can there be such disagreement?
Jim Green − national nuclear campaigner, Friends of the Earth, Australia
The never-ending debate over the Chernobyl cancer death toll turns on the broader debate over the health effects of low-level radiation exposure.
The overwhelming weight of scientific opinion holds that there is no threshold below which ionising radiation poses no risk. Uncertainties will always persist. In circumstances where people are exposed to low-level radiation, public health (epidemiological) studies are unlikely to be able to demonstrate a statistically-significant increase in cancer rates. Cancers are common diseases and most are multi-causal. Other complications include the long latency period for some cancers; and limited or uneven data on cancer incidence and mortality. The upshot is that cancer incidence and mortality statistics are being pushed up and down by a myriad of factors at any point in time and it becomes impossible or near-impossible to isolate any one factor.
While the overwhelming weight of scientific opinion holds that there is no threshold below which radiation exposure is harmless, there is less scientific confidence about how to quantify the risks. Risk estimates for low-level radiation exposure are typically based on a linear extrapolation of better-understood risks from higher levels of exposure.
This 'Linear No Threshold' (LNT) model has some heavy-hitting scientific support. For example a report in the Proceedings of the National Academy of Sciences states: "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."1 Likewise, the 2006 report of the US National Academy of Sciences' Committee on the Biological Effects of Ionising Radiation (BEIR) states that "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."2
Nonetheless, there is uncertainty with the LNT model at low doses and dose rates. The BEIR report makes the important point that the true risks may be lower or higher than predicted by LNT − a point that needs emphasis and constant repetition because nuclear apologists routinely conflate uncertainty with zero risk. That conflation is never explained or justified; it is simply dishonest.
The UN Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and the International Commission on Radiological Protection recommend against using collective dose figures and risk estimates to estimate total deaths. The problem with that recommendation is that there is simply no other way to arrive at an estimate of the death toll from Chernobyl (or Fukushima, or routine emissions from the nuclear fuel cycle, or weapons tests, or background radiation, etc).
Indeed UNSCEAR itself (PDF) co-authored a report which cites an estimate from an international expert group − based on collective dose figures and risk estimates − of around 4,000 long-term cancer deaths among the people who received the highest radiation doses from Chernobyl.3 And UNSCEAR doesn't claim that low-level radiation exposure is harmless − its 2010 report 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."4
The view that low-level radiation is harmless is restricted to a small number of scientists whose voice is greatly amplified by the nuclear industry (in much the same way as corporate greenhouse polluters and their politicians amplify the voices of climate science sceptics). In Australia, for example, uranium mining and exploration companies such as Cameco, Toro Energy, Uranium One and Heathgate Resources have sponsored speaking tours by Canadian junk scientist Doug Boreham, who claims that low-level radiation exposure is beneficial to human health. Medical doctors have registered opposition to this dangerous quackery and collusion.5
About 50 people died in the immediate aftermath of the Chernobyl accident. Beyond that, studies generally don't indicate a significant increase in cancer incidence in populations exposed to Chernobyl fallout. Nor would anyone expect them to because of the data gaps and methodological problems mentioned above, and because the main part of the problem concerns the exposure of millions of people to low doses of radiation from Chernobyl fallout.
For a few fringe scientists and nuclear industry insiders and apologists, that's the end of the matter - the statistical evidence is lacking and thus the death toll from Chernobyl was just 50. (If they were being honest, they would note an additional, unknown death toll from cancer and from other radiation-linked diseases including cardiovascular disease). But for those of us who prefer mainstream science, we can still arrive at a scientifically defensible estimate of the Chernobyl death toll by using estimates of the total radiation exposure, and multiplying by an appropriate risk estimate.
The International Atomic Energy Agency estimates a total collective dose of 600,000 person-Sieverts over 50 years from Chernobyl fallout.6 Applying the LNT risk estimate of 0.10 fatal cancers per Sievert gives an estimate of 60,000 deaths. Sometimes a risk estimate of 0.05 is used to account for the possibility of decreased risks at low doses and/or dose rates (in other words, 0.05 is the risk estimate when applying a 'dose and dose rate effectiveness factor' or DDREF of two). That gives an estimate of 30,000 deaths.
On the other hand, LNT may underestimate risks. The BEIR report states that "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." Likewise the BEIR report states: "The committee recognizes that its risk estimates become more uncertain when applied to very low doses. Departures from a linear model at low doses, however, could either increase or decrease the risk per unit dose." So the true death toll could be lower or higher than the LNT-derived estimate of 60,000 deaths.
A number of studies apply that basic method − based on collective radiation doses and risk estimates − and come up with estimates of the Chernobyl cancer death toll varying from 9,000 (in the most contaminated parts of the former Soviet Union) to 93,000 deaths (across Europe).
UN reports in 2005-06 estimated up to 4,000 eventual deaths among the higher-exposed Chernobyl populations (emergency workers from 1986−1987, evacuees and residents of the most contaminated areas) and an additional 5,000 deaths among populations exposed to lower doses in Belarus, the Russian Federation and Ukraine.7
The estimated death toll rises further when populations beyond those three countries are included. For example, a study by Cardis et al reported in the International Journal of Cancer estimates 16,000 deaths.8 Dr Elisabeth Cardis, head of the Radiation Group at the World Health Organization's International Agency for Research on Cancer, said: "By 2065 (i.e. in the eighty years following the accident), predictions based on these models indicate that about 16,000 cases of thyroid cancer and 25,000 cases of other cancers may be expected due to radiation from the accident and that about 16,000 deaths from these cancers may occur. About two-thirds of the thyroid cancer cases and at least one half of the other cancers are expected to occur in Belarus, Ukraine and the most contaminated territories of the Russian Federation."9
UK radiation scientists Dr Ian Fairlie and Dr David Sumner estimate 30,000 to 60,000 deaths.10 Dr Fairlie notes that statements by UNSCEAR indicate that it believes the whole body collective dose across Europe from Chernobyl was 320,000 to 480,000 Sv, from which an estimate of 32,000 to 48,000 fatal cancers can be deduced (using the LNT risk estimate of 0.10).11
According to physicist Dr. Lisbeth Gronlund: "53,000 and 27,000 are reasonable estimates of the number of excess cancers and cancer deaths that will be attributable to the accident, excluding thyroid cancers. (The 95% confidence levels are 27,000 to 108,000 cancers and 12,000 to 57,000 deaths.) In addition, as of 2005, some 6,000 thyroid cancers and 15 thyroid cancer deaths have been attributed to Chernobyl. That number will grow with time. Much lower numbers of cancers and deaths are often cited, but these are misleading because they only apply to those populations with the highest radiation exposures, and don't take into account the larger numbers of people who were exposed to less radiation."12
A 2006 report commissioned by Greenpeace estimates a cancer death toll of about 93,000.13 According to Greenpeace: "Our report involved 52 respected scientists and includes information never before published in English. It challenges the UN International Atomic Energy Agency Chernobyl Forum report, which predicted 4,000 additional deaths attributable to the accident as a gross simplification of the real breadth of human suffering. The new data, based on Belarus national cancer statistics, predicts approximately 270,000 cancers and 93,000 fatal cancer cases caused by Chernobyl. The report also concludes that on the basis of demographic data, during the last 15 years, 60,000 people have additionally died in Russia because of the Chernobyl accident, and estimates of the total death toll for the Ukraine and Belarus could reach another 140,000."
Those are the credible estimates of the eventual death toll from Chernobyl. Another defensible position (or non-position) is that the long-term cancer death toll is unknown and unknowable because of the uncertainties associated with the science. The third of the two defensible positions, unqualified claims that the death toll was just 50, should be rejected as dishonest or uninformed spin from the nuclear industry and some of its scientifically-illiterate supporters ... and from every last one of the self-proclaimed pro-nuclear environmentalists − James Hansen, Patrick Moore, Mark Lynas, George Monbiot, James Lovelock, etc.
1. Brenner, David, et al., 2003, 'Cancer risks attributable to low doses of ionizing radiation: Assessing what we really know', Proceedings of the National Academy of Sciences, November 25, 2003, vol.100, no.24, pp.13761–13766,
2. US Committee on the Biological Effects of Ionising Radiation, US National Academy of Sciences, 2006, 'Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2', www.nap.edu/books/030909156X/html
3. The Chernobyl Forum: 2003–2005, 'Chernobyl’s Legacy: Health, Environmental and Socio-Economic Impacts and Recommendations to the Governments of Belarus, the Russian Federation and Ukraine', Second revised version, p.16, www.iaea.org/Publications/Booklets/Chernobyl/chernobyl.pdf
4. UNSCEAR, 2010, Report of the United Nations Scientific Committee on the Effects of Atomic Radiation on the Effects of Atomic Radiation 2010',
5. Doctors' response to Toro Energy's junk science:
Doctors' response to Cameco's junk science:
6. IAEA, 1996, "Long-term Committed Doses from Man-made Sources," IAEA Bulletin, Vol.38, No.1,
7. Chernobyl Forum, 2005, 'Chernobyl's Legacy: Health, Environmental and Socio-Economic Impacts', www.iaea.org/Publications/Booklets/Chernobyl/chernobyl.pdf
World Health Organization, 2006,
8 Cardis E, Krewski D, Boniol et al, 'Estimates of the Cancer Burden in Europe from Radioactive Fallout from the Chernobyl', International Journal of Cancer, Volume 119, Issue 6, pp.1224-1235, Published Online: 20 April 2006,
9. Cardis, Elizabeth, 2006, www.iarc.fr/en/media-centre/pr/2006/pr168.html
10. Ian Fairlie and David Sumner, 2006,' The Other Report on Chernobyl', www.chernobylreport.org
12. Lisbeth Gronlund, 17 April 2011, 'How Many Cancers Did Chernobyl Really Cause?', http://allthingsnuclear.org/post/4704112149/how-many-cancers-did-chernob...
13. Greenpeace, 2006, 'The Chernobyl Catastrophe − Consequences on Human Health',
TORCH: The other Chernobyl report
Published in WISE Nuclear Monitor #820, 16 March 2016, www.wiseinternational.org/nuclear-monitor
"Think again, think seven times again before you leap and start construction of new nuclear power plants. With my experience of Chernobyl I know what is involved. The explosion of one reactor required a superpower country to spend tens of billions of roubles. Still there was the longer pollution of the soil, the deaths of a number of people and consequences that will be far reaching." – Mikhail Gorbachev, 20061
Global 2000 / Friends of the Earth Austria has released an updated dated version of an important report on the Chernobyl health impacts.2 Written by radiation biologist Dr Ian Fairlie, the report incorporates the findings of many relevant studies produced in the 10 years since the original 'TORCH' report was published.
The subject matter is inordinately complex but Fairlie explains a host of technicalities in language that anyone can understand. Thus the report is not only an invaluable, up-to-date report on the health effects of the Chernobyl disaster, but it also doubles as a good primer on the radiation/health debates.
Fairlie summarizes the main impacts:
- 5 million people in Belarus, Ukraine and Russia still live in highly contaminated areas, and 400 million people in less contaminated areas.
- 37% of Chernobyl's fallout deposited on western Europe; 42% of western Europe contaminated.
- Initially, about 116,000 people were evacuated, and later an additional 230,000 people were resettled.
- 40,000 fatal cancers predicted across Europe (based on an estimated collective dose of 400,000 person-Sieverts and a linear no-threshold derived risk estimate of 0.1 fatal cancers per person-Sievert).
- 6,000 thyroid cancer cases to date, 16,000 more expected.
- Increased radiogenic thyroid cancers now seen in Austria: 8–41% of increased thyroid cancer cases after 1990 in Austria may be due to Chernobyl.
- Increased incidences of leukemia well established among the clean-up workers in Ukraine and Russia with very high risk factors. Slightly lower leukemia risks were observed among residents of seriously contaminated areas in Ukraine and Belarus. Indications of increased leukemia risks among infants have been observed in Slovakia, Germany, Greece, Italy and Belarus, but research that would clarify the matter has been stalled mainly by lack of funding.
- Increases in solid cancers were observed among clean-up workers in Belarus and Ukraine but their relative risks (20% to 50%) were considerably lower than the 700% increases observed for thyroid cancer, and the 200% to 500% increases observed for leukemia.
- Several new studies have confirmed increased risks of cardiovascular disease and stroke after Chernobyl. It is recommended that further studies be funded and carried out on radiogenic cardiovascular diseases. As current radiation dose limits around the world are based on cancer risks alone, it is recommended that they should be tightened to take into account cardiovascular disease and stroke risks as well.
- A recent very large study observed statistically significant increases in nervous system birth defects in highly contaminated areas in Russia, similar to the elevated rates of such birth defects observed in highly contaminated areas in Ukraine. The International Agency for Research on Cancer should be funded to carry out a comprehensive study of birth defects, particularly nervous system defects and Down Syndrome after Chernobyl.
The report notes that many restrictions on contaminated foodstuffs have now been lifted but they remain in some areas on wild reindeer, boar, deer, wild mushrooms, berries and carnivore fish. Areas of Germany, Austria, Italy, Sweden, Finland, Lithuania and Poland still have raised caesium-137 contamination levels in natural or wild foodstuffs. Caesium-137 contamination will persist for a long time into the future (as is also the case in Fukushima Prefecture).
The report states that recent studies provide strong evidence of decreased health indicators among children living in contaminated areas in Belarus and Ukraine, including impaired lung function and increased breathing difficulties lowered blood counts high anaemia levels and more colds, and raised levels of immunoglobulin fluctuation.
Fairlie reflects on the ill-health of children:
"A health factor which has received insufficient consideration in epidemiology studies is the general poor health of children still living in highly contaminated areas in Belarus, Ukraine and Russia.
"In adults, many commentators have remarked on the marked general deterioration in health indicators in Belarus, Ukraine and Russia. For example, between 1990 and 2005, the average lifespan for a male adults in Russia decreased from 70 to 61 years and in the Ukraine from 67 to 61 years: in western Europe, the average male life span is >75. Some of the complex factors involved in the considerable declines in health indicators in Belarus, Ukraine and Russia are described in [a 2002 United Nations Development Programme] report. However without access to government data, it is difficult to assess whether continued exposures to low residual levels of radioactivity are a factor.
"But it is not just adult life expectancy: anecdotally many children complain of ill health and many visitors remark on the poor health status of children in badly affected areas. Western science, of course, demands epidemiological evidence rather than anecdotal reports but this evidence has not been available – often due to the lack of central funding.
"However these problems have appeared so acute and clear to thousands of non-medical lay visitors and to medical staff that in the 1990s and 2000s they established charities to bring the children of Chernobyl to their own countries in the West (including US and Canada) for temporary respites from high radioactivity levels. Scores of these NGOs now exist at international, national and local levels and each year they bring thousands of Chernobyl children to their own countries and homes. Without exception, these groups observed improvements in the health of invited children.
"In the past, these groups were unfortunately ignored on the grounds that the observed improvements in these children were subjective and due to the improvements in outlook and temperament that everyone experiences on holiday.
"Recent authoritative studies have shed much-needed light on this matter: they indicate beyond reasonable doubt that radiation exposures to children living in contaminated areas are implicated in their poor healths. It is therefore unsurprising that their healths improve when they visit abroad."
The report notes that civil society has partially filled the void left by governments and nuclear agencies:
"Unfortunately some international nuclear agencies and national authorities remain in denial about the
scale of the health disaster caused by Chernobyl. This is shown by their continuing refusal to devote resources to humanitarian aid, rehabilitation and disaster management.
"This is regrettable: however there is one silver lining. Many thousands of concerned citizens throughout the world have mobilised to help stricken people in the three countries most seriously affected. Hundreds of local, national and international voluntary groups have been established especially to help the children in these areas. This help includes visits abroad for tens of thousands of children to provide respites from their radioactively contaminated homelands. This report provides strong epidemiological evidence that such visits are indeed helpful.
"Hundreds of doctors from many countries also work pro bono in contaminated territories, helping to minimize Chernobyl's health consequences.
"These humanitarian actions are sorely needed and welcome. They constitute a silent rebuke of the disregard shown by some international nuclear agencies and national authorities towards the continuing plight of affected children in Belarus, Ukraine, and Russia."
Fairlie argues for improved preparedness for future accidents by means of the following:
- providing stable iodine to all citizens within at least 30 km of all nuclear reactors;
- stocking emergency levels of radioactivity-free water supplies, long-life milk and dried food supplies;
- distributing information leaflets to the public explaining what to do in the event of an emergency and explaining why precautionary measures are necessary;
- planning evacuations;
- constructing and staffing permanent emergency evacuation centres;
- carrying out emergency evacuation drills;
- planning subsequent support of evacuated populations;
- planning how to help those who choose to remain in contaminated areas; and
- increasing the mental health training of primary physicians and nurses.
1. Reuters, 9 June 2006, 'Gorbachev warns against new nuclear power plants'
2. Ian Fairlie, March 2016, 'TORCH-2016: An independent scientific evaluation of the health-related effects of the Chernobyl nuclear disaster',