Recently for some reason there has been discussion of the dangers of nuclear power. People have been casting their memories back to that most famous of disasters, Chernobyl, when things went slightly pear-shaped in a communist dictatorship, and a rather backward and poorly-designed, badly-run nuclear plant went critical. Now there is a 30km wide exclusion zone around the location of the disaster, which has become a nature reserve, and indeed now the Ukrainian government allows package tours. Also, lots of people work in the exclusion zone maintaining the sarcophagus on the power plant itself. So is radiation deadly, that all these things can happen in the space of 20 years from a disaster rated as the worst possible form of nuclear accident?

At the moment in Japan a lot of people are very scared of a radiation leak or meltdown at the Fukushima plant, and indeed I know of one American in Beppu – 1000 km from the Fukushima site – who has fled the country, and two others who are being urged to by their family. My Father asked me to leave Japan when I was in Tokyo, which is 200 kms from the Fukushima site. How worried should we be about radiation releases from Fukushima? How strong is the evidence from Chernobyl about the dangers of nuclear power, and should we conclude from the ecological evidence that it is too dangerous to use safely?

Bomb Exposure

We can examine some of this information from reference to existing research in Japan, which hosts the excellent Radiation Effects Research Foundation, whose English-language guide to the health effects of radiation gives clear information about the health effects of the original atomic bombs. It’s surprising to discover that the radiation effects of the bombs, though noticeable, are not so powerful as one might suspect. Those exposed within 2500 m of the epicentre had an average increase in risk of solid cancers of 10%, in leukaemia of 46% amongst all survivors, and in some cases specific cancers can be attributed to the effects of the bomb. It’s worth noting that these effects aren’t very large in comparison to smoking, for example, which has an attributable risk for all cancers of about 30%[1], or a relative risk of lung cancer death (not just lung cancer morbidity) of about 23. So it’s pretty clear that while atomic bombs are very very nasty (with very high fatality numbers in both Nagasaki and Hiroshima) their radiation effects are actually no worse than smoking – which the WHO estimates has 50% prevalence amongst men in Japan[2].

Meltdown Exposure

Bombs have a different main means of exposure, though – radiative  rather than consumed. Radioactivity from nuclear accidents is breathed in, drunk, or consumed as part of the food chain. So maybe cancer rates differ markedly. I know from conference presentations in Australia that the RERF also does a lot of research on this issue (I saw a very interesting presentation on a nuclear weapon research institute in a closed city further East from Chernobyl in the old USSR that was very, very badly managed), but this is much more broadly researched, and the conclusion again seems to be that radiation released from nuclear plants in serious accidents is not that dangerous – especially to adults[3]. This paper, for example, gives detailed estimates of the burden of disease in Europe grouped by exposure category. It includes estimates of the “attributable fraction,” the proportion of deaths to cancer that might be due to exposure to radiation from Chernobyl. Table 1 shows the attributable fraction for all cancers except leukaemia, thyroid and skin cancers. In the area immediately around the plant (the highest exposure levels) this is 0.23%; in the furthest areas of Western Europe it is 0%. The equivalent attributable fraction for leukaemia is 0.66% for those in the area immediately around the plant. For thyroid cancer in children, the attributable fraction in the most heavily exposed areas is 20% (Table 2); but note that this amounts to an average of 6000 cases in 2.7 million children. This is not a high risk event! Compare this with lung cancer amongst smokers (30%), and think of all the men you know who smoked who are still alive at the age of 70 or 75. While anything that increases your risk of death is bad, the reality is that Chernobyl was a pretty weak cause of cancer in even the most intensely exposed children.

These results are also supported by this paper, which concludes that

It is unlikely that the cancer burden from the largest radiological accident to date could be detected by monitoring national cancer statistics. Indeed, results of analyses of time trends in cancer incidence and mortality in Europe do not, at present, indicate any increase in cancer rates—other than of thyroid cancer in the most contaminated regions—that can be clearly attributed to radiation from the Chernobyl accident

So, it appears that thyroid cancer is an issue amongst children heavily exposed to a post-meltdown radiation release. But what about adults?

Amongst adults there is a group of study subjects who were heavily exposed in Chernobyl, and who have been reported on by various researchers  – the 72000 people referred to as the “liquidators,” people whose job was to decontaminate the area around the site as best they were able to. The Greenpeace report on Chernobyl[pdf] contains illustrative tables drawn from papers about these people, which show estimates of their excess risk of all cancers (page 33). These estimates range from a relative risk of 1.11 to 2.62, and an all-cause relative risk of about 1.25. That is, a 25% increased risk of any cancer. These people were deeply exposed to radiation, probably without proper protective equipment in situations of hard labour, and yet they can’t muster a relative risk of any cancer that exceeds that of regular smokers (or even ex-smokers). There are, in fact, still 400 or so people living illegally within the Chernobyl exlusion zone even now. If you do calculations based on the tables in page 33 for the 300,000 people evacuated from the area around the Fukushima plant – that is, if you assume they were all working as liquidators instead of fleeing to Tokyo – you’ll find the entire group would experience between 1200 and 12000 extra cancers, depending on whether there is a misprint in the tables in the Greenpeace report (if there is a misprint it’s 12000, otherwise it’s 1200). Now, those people aren’t working as liquidators, so even if they stayed in their homes after a complete meltdown of the Fukushima plant, they’d probably experience a risk of cancer less than 25% higher than background levels.

A 25% elevated risk of cancer is bad, true, but it’s not catastrophic – especially for the 50% of men already at 20 times the normal risk of cancer due to smoking.


Radiation release from a reactor meltdown situation is a scary thought, but it’s nowhere near as dangerous as the media are presenting. The Chernobyl reactor meltdown was almost certainly more serious than an “equivalent” meltdown in Fukushima (Chernobyl was a graphite core without a containment unit) and it led to an average increase in cancer risk of less than 25% in those immediately around the plant and exposed to radiation. This was in a situation with a botched evacuation, before people understood the risks. In fact, the proportion of cancers attributable to Chernobyl in adults immediately around the plant at the time of the fire is less than 1%. Unless one is actively working in radiation remediation, the risks are minimal. For children the risks are much more serious, but even then the risk of thyroid cancer is very low, because thyroid cancer is a very very rare disease. Amongst 2.7 million children immediately exposed to high radiation levels around Chernobyl there were perhaps 6000 thyroid cancers attributable to the accident. This is a serious and preventable problem, but a death sentence for exposed children it is not.

As  a final note, Facebook Japan has been providing regular updates on the disaster and recently published a comment from the UK Embassy, who had a teleconference withe the UK Chief Scientist. Their conclusion based on what he told them:

In case of a ‘reasonable worst case scenario’ (defined as total meltdown of one reactor with subsequent radioactive explosion) an exclusion zone of 30 km would be the maximum required to avoid affecting peoples’ health. Even in a worse situation (loss of two or more reactors) it is unlikely that the damage would be significantly more than that caused by the loss of a single reactor.


The experts do not consider the wind direction to be material. They say Tokyo is too far away to be materially affected.

Compared to the risk of death by radiation exposure, you are much, much more likely to die of a traffic accident, or a serious aftershock, than you are a meltdown – a full meltdown, not the current steam explosions – in Fukushima.

fn1: Chou P, Nomura A, Stemmermann G. A prospective study of the attributable risk of cancer due to cigarette smoking. American Journal of Public Health, 1992 January; 82(1): 37–40.

fn2: It’s worth noting though that the figures for cancer death in survivors of atomic bombs are highly biased. For a start, they’re given based on averages; there is a linear relationship between exposure and solid cancer prevalence, with those closer to the blast site having 50% increased risk. But particularly, lots of people in the blasts died immediately of other causes, which creates a potential survivor bias in that perhaps only those who were sheltered from the initial blast enter the long-term calculations for cancer risk. One shouldn’t infer from studies of atomic bomb survivors that radiation is not a significant and nasty after-effect of atomic attack. Not to mention that modern weapons are nuclear, not atomic, and much much more violent than those used 60 years ago.

fn3: And, kids, if you’re reading this blog, I suggest you go talk to your parents right now and ask them the meaning of the words “parental supervision.” You shouldn’t be reading my blog.