What Level of Risk Justifies Denying People Their Homes? A Look at Fukushima vs Pollution in Big Cities

I was very moved after hearing the heartfelt testimonies of teacher Yoshiko Aoki, high-school student Moe Harada, and a group of students dialling in from Fukushima to the OECD NEA risk communication workshop in Paris. I previously shared with you their Stories from Tomioka town, Fukushima. But I felt that I needed to do more – I wanted to honour the last plea the students made before they hung up:

“Everyone should try to know the real facts about Fukushima.”


Within Tomioka town there are still off-limits areas barred with metal fences.

I have tried to do just that. I looked for information on the areas that were so painful for the teacher, Ms Aoki to see: where inhabitants of Tomioka town are still barred from entering. Although coming back to their homes in 2017 was cause for happiness and an opportunity to finally begin to heal for Aoki and more than a thousand others, the existence of these off-limit areas sounded from her account like wounds in the town itself.

“There are barriers in our town, where people are forbidden to go.”

In this piece write about my attempt to understand the kind of risks the authorities were protecting their people from with such extreme measures.


Tomioka town. Green: evacuation order lifted. Yellow: businesses allowed, living prohibited. Pink: still off-limits.

The areas denoted by yellow in the map here are estimated by the officials to yield a total dose of between 20 to 50 mSv/year. In these areas, businesses are allowed but habitation is largely prohibited.

These levels, although notably higher than the typical global range of 1 to 13 mSv/year, are not exceptional. They are in the same class with natural background in Kerala, India, where  total doses can reach 40 mSv/year. No increase in cancer rates in the area have been observed.

The pink ‘difficult to return’ area is described as yielding an estimated dose of ‘above 50 mSv/year.’

Looking at the more detailed dose survey map of Fukushima coast, the measurement points with ambient radiation levels yielding more than 83 mSv/year – see orange and red dots in the map below – number only eight all in all. The one red dot, more than 166 mSv/year, is found very near the power plant. But none of these eight are located in Tomioka town, which is the area around the dark blue dot on the lower edge of the coast.


Japanese map of radiation surveys. Grey patch on the coast is the Daiichi nuclear plant. Tomioka town is half-way down the remaining coast from there.

In the larger Fukushima area, the yellow (33-83 mSv/year) points represent a narrow band among a sea of darker greens and blues (dark greens yielding ambient doses of below 16 mSv/year and blues below 4 mSv/year).

There are factors other than ambient radiation to consider, but the potential ingestion of radioactive caesium, for instance, is unlikely to result in a very large dose. Studies in Chernobyl find that caesium does not accumulate anywhere in the body, and thanks to its long half-life, decay happens infrequently – its fate is much like that of the small amount of radioactive potassium we ingest in bananas and other foods.

The surveys of Tomioka town itself (see zoomed in map below) are all green or blue, which means the ambient radiation are at levels below 33 mSv/year.


Tomioka survey points. Light green: below 33 mSv/year, dark green: below 16 mSv/year. Blues: below four, two and one mSv/year.

But even if the ‘difficult to return’ areas would yield a total dose of well over 50 mSv/year, what would the size of the actual risk be?

Let’s assume, for the sake of argument, that the exposures in these off-limits areas would reach or surpass 100 mSv/year. This magnitude of background levels are naturally found in Ramsar, Iran, as well as at a famous Guarapari beach in Bazil, where people come for the supposed healing properties of the black radioactive sand.

After decades of epidemiological radiation research, scientific reviews can’t confirm discernible health effects from radiation below 100 mSv (UNSCEAR, McLean et al 2017). Although the correlations between 100-200 mSv are noisy enough to show both positive and negative correlations, at least in cases where exposures are acquired over a short period of time (such as among atomic bomb survivors), it is possible to determine a slight increase in cancer risk at doses above 100 mSv/year.

Common scientific estimate consider there to be a 5 % increase in cancer incidence with an exposure of 1000 mSv, or 1 Sievert (likely in a shorter time-frame than a year – but let’s assume, for a cautious estimate, for it to be per year).

By going back to live in the pink ‘difficult to return’ areas of Fukushima, in other words, the population there could perhaps have an increase in life-time cancer incidence of about 0.5 % (on top of the baseline life-time cancer risk of 40 %).

It’s fear, not level of risk, that is keeping people out of Fukushima

It’s startling to realize that a government would deny people the right to their homes for such a small increase in risk. What if should apply the same logic to other industrial pollutants – like particulate matter in air? The pollution from burning fossil fuels and wood, as well as traffic exhausts has long been known to cause serious health effects, including increased risk of cancers, heart disease, and respiratory illnesses.

who air pollution limits

Fukushima prefecture has average PM2.5 levels of 10 μg/m3, while Tokyo is at 13, with few pockets of 16-17 μg/m3.

Fukushima prefecture has relatively good air quality. If people from Fukushima would decide to move 200 km south to live in the relatively clean megacity of Tokyo, their risk of premature death due to air pollution would increase by about 1.8 %, on average. If they were unlucky enough to pick the areas in Tokyo with the most polluted air (Kuki or Koshigaya), however, their risk of death would go up by almost 5 % – the equivalent of 1000 mSv/year radiation exposure.

The air quality on the Fukushima coast just a few km from Tomioka town, as I am writing this, is well below the WHO recommended limit: PM2.5 concentration of 10 of μg/m3, equivalent to an Air Quality Index or AQI of 42. At this level, the WHO concludes that no increase in long-term mortality is observed.

shimokobana fukushima air quality

The World Air Quality Index. Detail view (the score 5 on the left) of Shimokobana on Fukushima coast in the north, few km away from Tomioka town. Tokyo in the south.

The large aggregation of stations in the Tokyo area in the bottom of the map shows that, unfortunately, even a relatively clean metropolis regularly crosses that air pollution limit (yellow stations above).

Should we see these areas, or indeed, most of Tokyo, barred off with metal fences as has been done with the northern parts of Tomioka town? Moving to Tokyo would triple the populations’ increase in risk of death, compared to moving them back to the remaining off-limits zones in Fukushima.

Considering the risks are larger, how come are the people allowed to move to Tokyo, but not allowed back on their ancestral lands?


The World’s Most Polluted Cities 2018 AirVisual. China, Korea, Japan.

To put this in further perspective still – the whole of Japan is a country where the air quality is good.

Merely crossing the sea over to South Korea or China would change the risk profile dramatically: 9-15 % increase in risk of premature death due to air pollution is the norm rather than the exception. In China and India particularly, there are places far worse affected, where the increases in risk is calculated in tens or hundreds of percents compared to areas of low particulate pollution, found commonly enough in places like the Nordics, France, Spain, Portugal, Canada, and large parts of the US.

Fukushima evacuated areas vs big cities air pollution

Most areas of the original Fukushima exclusion zone have background levels of below 4 mSv, which is within normal background range 1-13 mSv/year. Some still restricted areas are estimated to yield a total dose of 20-50 mSv/year, a level where scientists can not find health effects. The remaining off-limit areas, denoted as ‘above 50 mSv/year’ (also the US limit for nuclear workers), may not yield doses as high as 100 mSv, but in the graph above, this is the cautious assumption used, since extrapolation of risk below 100 mSv is not scientifically justified. The risk of increase in mortality would actually be lower still, as 0.5% is the theoretical risk of increase in life-time cancer-incidence, not mortality – you get the gist. This is a very cautious estimate.

Air pollution is a silent killer. Our industries impose the population to harmful emissions which cause an increase in heart and vascular disease, lung cancer, chronic obstructive pulmonary disease and respiratory infections. These effects are something far far worse and far-reaching than the possible small increase in risk due to radiation around the Fukushima nuclear plant. Yet the residents of Fukushima have been subjected to wrenching changes, and their life choices are still heavily dictated by regulations. These regulations are set by exaggerated caution due to fear, not by a realistic assessment of the context of risks.

By focusing blindly on making sure that radiation exposures remain extremely low, the people in charge have disregarded larger real risks, which they have imposed on their own citizens in the process.

I can only imagine what might have gone through Ms Aoki’s mind when she spoke to us in Paris, but in effect, her words sadly and accurately describe the conclusion I have found. As she so strikingly put it:

it’s people who destroyed Tomioka town.

the true risk of the nuclear accident

Ms Yoshida Aoki’s final reflections at OECD NEA Radiological Risk Communication workshop.

The consequences of the Daiichi nuclear accident have not been about the effects of the radioactivity on the body – but about the actions of people, tragically changing the lives of those living in parts of Fukushima prefecture like the Tomioka town.

The high-school student from Tomioka town, Ms Harada, who was eight years old at the time of the accident, told us:

“I want to be able to live in my home town without the fear of radiological risk.”

This is what we should to give these children: the freedom from fear, and from the kind of damaging decisions that can result from it.

We can’t allow our policies, governments, and regulatory agencies to continue reacting out of fear, and considering risks of radiation in a vacuum. It is a fundamental principle of bioethics that all medical students are taught throughout the world: that it may be better not to do something, or even to do nothing, than to risk causing more harm than good.

We must hold our government and regulatory bodies accountable to the same basic principle of ‘first, do no harm‘ – for the sake of the public they are supposed to be protecting.

logo basic

For further articles on radiation, you can read my pieces: Radiation and Cancer Risk – What Do We Know? and Radiation Exposures at a Glance. More on nuclear power found under Climate and Energy.

If you would like to have a discussion in the comments below, please take note of my Commenting policy. In a nutshell:

  1. Be respectful.
  2. Back up your claims with evidence.

About Thoughtscapism

Cell Biologist, science communicator, an agricultural and biodiversity analyst, and a fiction writer.
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7 Responses to What Level of Risk Justifies Denying People Their Homes? A Look at Fukushima vs Pollution in Big Cities

    • Hello Robert,

      Fixed it – this one should work better: https://www.unscear.org/docs/reports/2008/11-80076_Report_2008_Annex_D.pdf

      My reference is particularly for page 183:

      “In the dose range below 0.1 Sv, because of absence of persuasive evidence related in part to the substantial statistical uncertainties, the dependence of the frequency of adverse radiation effects on dose can be assessed only by means of biophysical models among which the model based on the LNT approach are the most popular. However, there are also others, including superlinear and threshold ones, and even models that account for a possible beneficial effect of radiation, termed hormesis. For these reasons, the Committee will not use these models to project absolute numbers of possible health effects in populations exposed to low doses of radiation, because of unacceptable levels of uncertainty in the predictions.”

      Thanks for reading and noticing!


  1. Alan Fellman says:

    Great article. You couldn’t be more correct in your assessment.

    Liked by 1 person

  2. Fred Steinkellner says:

    have recently read Catherine Ingram’s essay “Facing Extinction” in which is a reference to 42000 gallons of water used daily to keep the reactors cool. This led me to an article by Charles Digges on Bellona.org, in which he writes the Government is considering releasing this radioactive water into the oceans. What are your thoughts on this issue? Is it another case of fear being greater than risk?


    • Hello Fred,

      Thanks for your interest! Yes, this is a case of fear due to association. The Japanese officials have not released this perfectly safe water from holding tanks previously out of fear, not of radiation, but of the impact on public image. Mothers for Nuclear touched on this on their trip to Fukushima:

      “These tanks hold processed water that was removed from the basements of the reactor buildings. Although the water has been filtered and cleaned up, the presence of tritium, a mildly radioactive isotope of hydrogen, complicates the future of this water.

      Although the level of tritium in the water is far below levels that would have an impact on human health, the scientific perspective is not the only lens through which to view this issue (Conca, 2017). Officials are wrestling with the complicated issues of public perspective and stakeholder involvement – while the science says it’s safe, what will release of this water do to public opinion? Will the fishing industry be affected? Will public trust be affected? Will discrimination towards people and agricultural products from the prefecture persist? The situation requires careful consideration, and it is not a decision I envy.” https://www.mothersfornuclear.org/our-thoughts/2018/2/8/firsthand-in-fukushima

      And James Conca has also written about this.
      “Tritium is the mildly radioactive isotope of hydrogen that has two neutrons and one proton, with radioactivity so low that no environmental or human problems have ever come from it, even though it is a common radioactive element in the environment. Tritium is formed naturally by atmospheric processes as well as in nuclear weapons testing and in nuclear power plants.

      Let’s say that again – no harm has ever come to humans or the environment from tritium, no matter what the concentration or the dose.

      Tritium is just assumed to be carcinogenic to humans at extremely high levels, although that claim is only hypothetical since adverse health effects from tritium have never appeared in humans or in the environment. Only laboratory studies on mice at extremely high levels, only achievable in the laboratory, have shown any adverse health effects.

      Putting this water into the ocean is without doubt the best way to get rid of it. Concentrating it and containerizing it actually causes more of a potential hazard to people and the environment. And is very very expensive with no benefit.

      Unfortunately, the idea of releasing radioactivity of any sort makes most people cringe. But that’s the problem, only the perception of tritium is bad, not the reality. ” https://www.forbes.com/sites/jamesconca/2019/09/12/its-really-ok-if-japan-dumps-radioactive-fukushima-water-into-the-ocean/

      It appears that with anything radioactive associated with a nuclear power plant, the mere words are enough to make us feel there must be a problem. We are naturally biased to treat this unfamiliar, artificial source of threat that we don’t have intuitive sense for how to handle, as something that must be dangerous – more often than not we don’t wait to find for substantial support whether the threat is real or not.

      I hope this answer was useful to you. Thanks again for stopping by!

      Liked by 1 person

      • Fred Steinkellner says:

        Thank you Iida for your prompt and (as usual) calm rational response. Particularly the two links. The overwhelming volume of information available makes it extraordinarily difficult for the average person to arrive at a conclusive point of view but your blogs certainly help. On that note I wonder if you will write a blog(or series) on climate change?
        cheers, Fred


      • Thanks for your kind words Fred! I’m happy when I happen to have the time to answer promptly, and I try to be friendly and thorough (which makes it hard to have time to go through the entire backlog of commenters for some older posts..), great to hear you think I succeed 🙂

        Climate change is a very important topic and motivator for a majority of my posts, as you probably have noticed. I haven’t written as many posts about climate science specifically, but I do have two from several years back, one where I go through the various studies and surveys on consensus, and discuss the different ways of looking at it: https://thoughtscapism.com/2015/03/13/is-there-a-consensus-about-climate-change/

        I’ve also written one specifically on CO2’s role in warming the earth, here: https://thoughtscapism.com/2015/05/19/how-does-co%e2%82%82-warm-the-earth/

        I did have many long conversations about other aspects of climate science during my days as a moderator on energy and environment discussion forums, so I would have material for more posts, perhaps I should revisit them. Thanks for the suggestion!

        I’ve not ventured into the topic as much because I often found very good sources of info that go through the topic already. Everything from NASA and NOAA, and even respectable major newspaper sources – this Bloomberg visualisation of NASA data for instance is great: https://www.bloomberg.com/graphics/2015-whats-warming-the-world/

        As well as scientists-written blogs, like Skeptical Science (https://skepticalscience.com/), and I’ll give a special mention to two fellow skeptic/science bloggers who have done a lot of dives into the details: The Credible Hulk (him and I were moderating an energy-discussion forum together before starting either of our blogs and pages 🙂 ) https://www.crediblehulk.org/index.php/category/climate-science/

        And The Logic of Science, who is also a conservation biologist: https://thelogicofscience.com/tag/global-climate-change/

        If you have any favourite sources of climate science, please feel free to share them too!


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