Sunday 2 October 2011

Radiation 5

I've been busy recently and not able to stay up late writing this blog but the series I started on Radiation needs finishing. Where was I? I'd worked out that my possible exposure to radiation up until March next year might total 5.725 mSv per year. That's 2.1 mSv from external radiation, 2.13 mSv from medical (this includes 2 mSv from a planned mammogram), 0.285 mSv from air travel and 0.21 mSv internal radiation from breathing in the air. I should add more for food but frankly I have no idea how much I've taken in from food and water. I've been careful but food is not labelled so I just don't know. So, how much is too much? What levels are safe?

There are three kinds of exposure: 1) external, through the skin   2)  internal from breathing in radon gas and, in our case, radioactive particles in the air and, 3) internal radiation from food. Up until now the world operated on a limit of 1 millisievert per year for 1) and 2). There were no separate recommendations for food.

The 1 mSv/yr is an ICRP (International Commission for Radiological Protection) recommendation. (The ICRP is not a regulatory organisation. It advises and makes recommendations.) 1 mSv/yr was the world standard, a generous allowance that would cover infants, the aged and infirm. It was also recommended that radiation be avoided as far as possible. The world operated on this standard which is why people travel the world in safety and why dentists leave the room when they give an X-ray. 

Other pre-Fukushima recommended limits include: 5.2 mSv/yr  for people whose health is being properly monitored (for example, aeroplane and hospital staff); 20 mSv/yr for adult males working in the nuclear industry; 50 mSv/yr when children should be given iodine pills to prevent  thyroid cancer; 100 mSv/yr when there is a noticeable increase (0.05%) in the risk of cancer (there is wide concensus on this based on extensive long term research on Hiroshima and Nagasaki victims). Several hundred mSv will make your hair fall out (radiotherapy) and a single dose of several thousand mSv will kill you.

So what happened after the accident at Fukushima Daiichi? First, people were evacuated from a concentric zone 20 km around the plant where levels could reach over 50 mSv, and people in the 20 to 30 km zone (10 to 50 mSv) were ordered to stay indoors. It was all very confusing. Some experts were saying that levels of  100 mSv/yr were OK and  the government announced that there was 'no immediate risk to health'. Then when it became apparent that the danger was radioactive particles from the hydrogen explosions carried by the wind and dropped by the rain over a wide and disparate area, a new 'emergency' level of 20 mSv/yr was set (in consultation with ICRP). These so-called 'hot spots' continue to be discovered and households with children are given the option to evacuate. So suddenly 20 mSv/yr, the level that previously was safe for adult males wearing protective clothing being properly monitored and working of their own volition in a dangerous industry, was applied to everyone, including pregnant women and infants. One academic resigned from a government committee in tears saying 20 mSv/yr was too high for children. After that the government said that people should try and keep their exposure to 5 mSv/yr. Another idea that was floated was that 100 mSv over a lifetime is safe.

Then there's the question of food. Up to now there were no standards. The government introduced new 'provisonal' limits for different foodstuffs. The limits for caesium are 200 bq/kg for water, milk and dairy products and 500 bq/kg for meat, fish and vegetables. If everything you ate or drank from five categories was up to the limit, you'd take in 5 mSv/yr from food - which is deemed safe. Obviously most of the food you eat is hopefully free of contamination but the standards are controversial. Is it safe for children to take 5 mSv a year from food? That's equivalent to 100 X rays so to the layperson it doesn't seem safe.

Wade Allison in his book Radiation and Safety argues that the ICRP level of 1 mSv/yr is far too low, and furthermore that this low level in itself creates fear. He accuses the ICRP of ignoring scientific evidence that shows that people can take a lot more radiation without showing ill effects. In particular he accuses the ICRP of using a linear method for their calculations. For example, if a 100 mSv dose increases the risk of cancer by 0.05%, then a 1 mSv dose will give one hundredth of this risk - a straight 45 degree rising line on a graph (if scale starts at 0 mSv, zero risk). He says this is not the case. Research on Hiroshima and Nagasaki victims and on rats show that people can take a lot of radiation with no increased risk at all. Only a high dose increases the risk when the line on the graph will suddenly jump up - an S-shape. He calls it the Non Linear Threshold. (Correction: Linear No Threshold. See Wikipedia for good explanation  Linear No Threshold Model) He also says the body is able to repair itself (that's why radiotherapy is given in small doses over time - one day being the repair time before the next dose).

He says that in 1951 a limit set by ICRP was 3 mSv per WEEK. In 1957 this was tightened to 5 mSv per YEAR for the public and 50 mSv for radiation workers. In 1990 these annual limits were reduced to the ones we have now, 1 mSv and 20 mSv respectively.  He also quotes bone cancer data from the luminous dial painters which show a whole-of-life threshold of 10,000 mSv. So he thinks 5,000 mSv per lifetime would be safe.

His conclusion is that climate change will wipe us ALL out so a relaxation in the limits for radiation and more nuclear power is on balance in everyone's interests. That was in 2009. I wonder what he thinks now?

This has got very long, I'm sorry. So what do I think? I think we're probably fine. But we've been on an emotional rollercoaster these last six months not helped by conflicting opinions, delays in revealing information (the SPEEDI map in particular), and the mantra after every disclosure that 'it poses no danger to health'. You could say we've been victims of Allison's 'culture of fear'. We also know that this is a new situation with no data so the experts are not going to be dogmatic. They'll have the results and the answers in 20 years time but that's not much comfort to us now. We are particularly concerned about effects on children and the fact that no separate limits are given for children.

People here are getting used to living with radiation. Levels are down. Today 0.8 μSv/hr in Koriyama (less than Cornwall). And we're learning to cope. The stress is probably worse than the radiation itself.


  1. Reassuring words, thank you :)

  2. Hello Anne,
    I have been reading your blog for a few weeks now. Thank you very much for sharing your research and thoughts, I find it very informative.
    Celine (Tokyo)

  3. Great words Anne.
    One comment about the 1mSv: in the nuclear industry, one of the major rule is ALARA "As low as reasonably achievable", meaning you should do your best to reduce dose in any way possible. The 1 mSv, defined as "external and artificial exposure", was set as a "best policy" easily achievable, so everybody signed on this.
    As you mentioned it, there is a big safety margin between this "best policy" and dangerous levels, hence the confusion. I still think we should keep this 1 mSv and communicate more towards people.

  4. I disagree with Matt's comments about just sticking with the "As Low As Reasonably Achievable" (ALARA) principle.

    Telling people that, "you've received a dose in excess of the recommended dose but it's ok. It's not harmful to health" just freaks people out and any amount of communication isn't that effective by that point after the accident because people start to mistrust the authority who set the ALARA standard in the first place...

    When you talk to people in Fukushima, they are confused and angry by what they see as conflicting advice from the government and various experts. Many residents have been exposed to higher doses than the ICRP recommendation of 1 mSv per year. They're then told that it's above the standard but it's not harmful to health. As a result, many Fukushima residents I've spoken to see this as revising upward the safety limit because people equate the standard to the maximum health limit. As a result, there's a wide sense of distrust of what the government is telling them and it makes people anxious.

    A higher, more realistic standard of safe radiation dose (backed by data, sound science and a reasonable safety margin) in the first place would probably have caused people less worry. But what exactly is this level?

  5. I'am getting really upset by all the figures quoted, the bottom line is that any radiation is bad for you, so please people don't fool yourself ,move as far away from any contamination.
    I got that wisdom from following a lecture about what happened to the people in Hiroshima about 30 years ago.
    Look after yourself, Nick

  6. I saw a program on the BBC the other day about Fukushima / Chernobyl / Nuclear power. One interesting thing about the Chernobyl disaster was that, other than the soldiers who were sent in to clear up with next to no protection, the biggest health consequences of the nearby population was not in fact cancer. There was a rise in thyroid cancer among children who were in the area (all of them survived by the way), but doctors noted most of all that the deterioration of mental health was a far bigger problem. People being forced to evacuate, communities being broken up, living with the fear of radiation, and turning to drink as an escape all took its toll on people's mental health.

    I wonder if this particular lesson has been learned in Fukushima.

  7. @Tak:
    Since there is a gray area between 1 mSv and 100 mSv per year, and since people have different resilience to radiations (children, pregnant women...), I think it is good to stick to the 1 mSv, even if it is difficult to explain. By the way, I just explained it in 4 lines.
    20 years ago in Europe and US, and recently in Japan, gvt was basically saying "you don't need to know, it is complicated", which lead to a profound mistrust when accidents happened.
    Well, it has to change now, I think we (nuclear industry and all) have to take the high road and try to clarify as much as possible the data, without oversimplifying it, because somebody will then say "you are hiding the truth".

    Disclaimer: I am an European, working in nuclear industry (and proud to be in it), living in Japan, loving this country and its people.

  8. Matt - That's very interesting that you're an insider in the nuclear industry.

    I agree that the nuclear industry Japan needs to be more open. From what I see as an outsider, there seems to be some disagreement among the expert about what is a "safe limit". And I can imagine it's tricky to explain risks, which is a probabilistic concept, to the wider public. Yet, by simplifying the discourse, everyone will suspect that the government is "hiding the truth", as you say.

    So it's down to you experts to educate us!