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Japan nuclear leak and tap water

Fergus Walsh | 17:48 UK time, Wednesday, 23 March 2011

News from Tokyo that radiation in the water supply is twice the level considered safe for infants is yet another worry for the citizens of Japan. The authorities there have recommended that people in the city do not allow babies under one to drink tap water. So how much risk is there?

As many people have pointed out, and has been mentioned here before, we are all exposed to radiation all the time, from the environment and from medical procedures like x-rays. The Health Protection Agency says the average dose per year in the UK is around 2.7 millisieverts (mSv), but is higher for people in some parts of the country. In Cornwall, the average annual radioactive radon dose to people is 7.8 mSv.

So what about Japan? There were reports that Tokyo's tap water contained, at one point, 210 becquerels of radioactive iodine per litre. That is twice the recommended limit of 100 becquerels for infants although below the 300 limit for adults. Becquerels is a measure of radiation emmitted whereas millisieverts is a measure of dosage on the body (there are many handy guides to these terms on the web).

Professor Richard Wakeford from the Dalton Nuclear Institute and visiting Professor of Epidemiology at Manchester University said the health effects would be extremely small. He calculated that drinking water for a year at the Japanese limit would give an infant a dose of 0.4mSv, so you would need to double that to get the effect of drinking water at the higher level of radiation for a year. Professor Wakeford said "in theory, there would be a very small additional risk of cancer, but in practice nothing more than you could expect to get from normal background levels of radiation".

So the extra risk from drinking tap water in Tokyo for a year would be far less than that of someone moving, say, from London to Cornwall for a year.

As several scientists have pointed out, the alert about drinking water in Tokyo is simply a sensible precautionary measure, based on the principle that if you can easily avoid risk, you should do so.

Dr Jim Smith, Reader in Environmental Physics at the University of Portsmouth said: "It should be emphasised that the limit is set at a low level to ensure that consumption at that level is safe over a fairly long period of time. This means that consumption of small amounts of tap water - a few litres, say - at twice the recommended limit would not present a significant health risk. I would expect that the recommendation not to drink tap water would also extend to women who are pregnant or breastfeeding."

Prof Wakeford added: "The primary objective is to limit the radiation dose to the thyroid gland of infants and young children, because it is well established that infants and young children are at the greatest risk from the accumulation of radioactive iodine in the thyroid. The contamination limits keep the resultant doses to tolerable levels."

Nonetheless, one bit of newswire copy said that the tap water alert in Tokyo was sending "anxiety levels soaring over the nation's food and water supply". Residents in Tokyo are reportedly clearing the supermarket shelves of tap water. On Sunday, milk, spinach and other vegetables from areas near the Fukushima plant were found to have radiation levels higher than regulated standards, but the Japanese authorities said it did not pose an immediate risk to health.

I do not mean to underplay the issue of the Fukushima nuclear leak. But the dangers from Tokyo tapwater do not bear any comparison with the earthquake and tsunami where there are currently nearly 9,500 confirmed dead and more than 14,700 people still missing.


  • Comment number 1.

    Fergus Walsh.

    "I do not mean to underplay the issue of the Fukushima nuclear leak. But the dangers from Tokyo tapwater do not bear any comparison with the earthquake and tsunami where there are currently nearly 9,500 confirmed dead and more than 14,700 people still missing."

    yet, although your blog is for "discussion of medical and health issues", you've managed four blog posts on the radiation aspects, but not a single one on, say, the excellent provision of emergency food/shelter/sanitation for the 500,000+ displaced Japanese citizens.
    go figure..

  • Comment number 2.

    It seems there is a lack of detailed information that people need for decision making purposes in their everyday life in Tokyo. What are the affects of bathing in this water for infants (all anyone writes about is drinking the water) in Tokyo? What are the levels of the other material that are potentially spewing out of the plant such as strontium and plutonium and the health consequences for exposure to these materials? What are "safe" levels for these other material ingested or put in contact through bathing or rain? What are the studies that these "reporters" or "correspondents" are utilizing in their reporting (they often sound biased or based on assumptions of personal versus scientific understanding on the subject)? Are all radiation equal in impact to health (background vs. natural vs. plane flight vs. x-ray vs. smoke/steam from a nuclear plant with MOX)? It would be great to see actual reporting by reporters or specialists on this type of information which I am unable to find anywhere. People are making decisions for their children based on incomplete reporting and this is "underplayed" from my perspective and impacting my loved ones in Japan.

  • Comment number 3.

    I think the comparison with CAT scans is misleading. They are not recommended unless truly necessary because of the high irradiation.

    A friend of mine underwent one and developed lymphoma within 3 years. Of course this may have been unrelated but who knows?

    Rather, the comparison perhaps should make people think twice about CAT scans.

  • Comment number 4.

    @Questions111 #2

    The risk to infants is from drinking and hence absorbing radioactive iodine into their bloodstream. There will be negligible risk from bathing etc.

    Also, when radiation is measured in sieverts, that takes into account how it is absorbed by the human body, rather than just radiation in the environment.

  • Comment number 5.

    Wonderful thing the Jet Stream.
    The fallout reached Iceland yesterday.
    France expected it to begin to land on them today.
    Perhaps a little more expert reassurance that radiation is nothing to worry will appear soon.

  • Comment number 6.

    My wife lives in Tokyo and she is 17th weeks pregnant.I'm wondering what's the potential risk for her and our far as I know iodine 131 present in tap water decay within 8 days so I presume risk of accumulation of radioactive particles in the body is unlike....however I'm still very concerned about their health...

  • Comment number 7.

    6. At 21:47pm on 23rd Mar 2011, tomwilk wrote:
    "... iodine 131 present in tap water decay within 8 days..."


    Half of it decays in 8 days, then half of what's left during the next 8 and so on.

    I gather that it's presently about twice recommended limit, so after 8-10 days it should conform, as long as there's no more input.

  • Comment number 8.

    "The fire released an estimated 740 Terabecquerels (20,000 curies) of iodine-131"
    (Taken from the summary of the Windscale Fire of Oct 1957.)

    This isotope has a half life of 8 days BUT is stored in many biological systems and the human, and other animal, Thyroid. #6 tomwilk note: the 8 days is a HALF LIFE - not vanishing completely - after 8 days only half of what you started with is left!

    How much has been released in Japan is unknown as yet, but some must have been released for it having been found. It is also being found in milk as it was in the UK in 1957.

  • Comment number 9.

    "But the dangers from Tokyo tapwater do not bear any comparison with the earthquake and tsunami where there are currently nearly 9,500 confirmed dead and more than 14,700 people still missing."

    Yes, because the earthquake and tsunami are over, so we, especially those living in Tokyo, don't face any more danger from them. However, the radiation crisis is ongoing and perhaps worsening, so we are more worried about that.

    I wish people who report on the situation at the nuclear plant would not feel obligated to always remind us that it is not as bad as the tsunami, as if we shouldn't complain about potentially having our water poisoned because somebody else has it worse. We are well aware of the destruction caused by the tsunami, but if you want to report further on the humanitarian crisis there, feel free to do so. But this has absolutely no bearing on the gravity of the situation in Tokyo.

  • Comment number 10.

    Why isn’t anyone talking about breast milk??
    Most of the children under 1 are also breast fed! Just like the cow’s milk with concentrated amount of radiation posing health risks to children wouldn’t breast milk be the same?
    What is the mother supposed to eat and breathe?? Shouldn’t mothers go out at all? How can we know wheat we are feeding our babies??

  • Comment number 11.

    just so folks know- the news in japan (mainly in japanese) is advising breast feeding and pregnant women to avoid the water for now. i am here in tokyo, and i am cutting back on the tap water i drink. but based on the recommendations, i am not afraid of drinking a little of it. people say there is no information, but i haven't found it that bad. however, if you're looking for information in english, it is a little slower to catch up usually, which is too bad. if i were pregnant or nursing, i would have already gotten out of tokyo. but since i am not, i am feeling okay t stay until the situation gets worse.

  • Comment number 12.

    Reality Check.. International levels for Iodine 131 in drinking water are 3,000 Bq/l vs. Japan's 300 Bq/l Source = WHO: see (pg: 11,12,13)

    "It should also be noted that the Japanese guideline value is an order lower than the internationally agreed Operational Intervention Levels (OIL's) for I-131 (3,000 Bq/kg), Cs-134 (1,000 Bq/kg) and Cs-137 (2,000 Bq/kg). Iodine-131 is not a significant source of radiation because of its low specific activity.."

  • Comment number 13.

    The other sign reads?

  • Comment number 14.

    Come on Fergus. Any chance of focusing on bans on all alcohol advertising and no alcohol used as a relief for soap characters?

    Advertising takes many forms and is increasingly insidious as laws change?

    So, Fergus, as you are respected as a BBC health journalist - why not stick your neck out or talk to your contacts and suggest:

    No alcohol advertising on television. Or anywhere else. FULL STOP.
    No alcohol consumption on soap operas by those characters enduring difficulties.

  • Comment number 15.

    What is the real reason for attempting to generate a panic? It seems like some companies are going to do very nicely out of fear generation.

  • Comment number 16.

    The biggest health problem for the Japanese is going to be the emotional scars of millions of people. The untimely death of friends and family and loss of home and treasured possessions is probably more immediate than the radiation issue which is probably more easy to deal with.

  • Comment number 17.

    This is important distinction! Airplane flights, chest X-rays and background radiation are a form of radiation you receive externally. The dose limits for these are only applicable for external radiation. Radioisotope fallout from a nuclear accident is different from these because all of the radiation is in a form of particles in the air, the water and soil. You can breath in these particles or consume them with your food or drink. The radiation dose then is dependent on their biological accumulation and longevity and the type of radiation they emit. The dose accumulates as long as the isotope remains in your body - for days, weeks or years. You must use isotope specific therapeutic dose limits (in rads or curie) to measure the potential health effects of contamination from fallout - not just external gamma radiation measured in Sievert. That is misleading and dishonest. Please interview someone who can explain this authoritatively to you, whom you can then quote. I recommend Dr. Helen Caldicott MD.

  • Comment number 18.

    We have heard that the water in Lake Union, near fishermans terminal and surrounding lakes of the Seattle area, are reporting elevated levels of radation from Japan. What more don't we know?

  • Comment number 19.

    Has anybody calculated the likely risk of fatalities associated with the travel miles that have been needed to fulfil some world government advice to their citizens to leave Japan.
    Many 10's of thousands of people travelling thousands miles.

    Whats the likelihood this turns out to be bad advice and cause more deaths than staying put!

  • Comment number 20.

    I watch Japanese TV program today.
    The program report that there are completely no disabilities at shelter on Sendai.
    What is this is mean?
    The report said that there are about 1,100 disabilities on Sendai.
    There are ZERO disabilities at ANY shelter, can you imagine?

    These disabilities hesitate visit shelter who concern that if they go shelter
    it cause problem what is need more space for toilet(use wheel chair), need more man power for help the people,etc.
    I can understood these concern because there are huge refugee at these shelter.
    Unfortunately, now we do not have enough man power for help people who is normal.
    I can understand that people's concern radiation very much if I were watch news report on your nations.
    However your concern move Media and media report more worse scenario,
    the report generate PANIC, and these disabilities got more tough environment.
    I guess that some Japanese write your concern,report,etc via Internet.
    I also understand that these Japanese behavior because they try to tell detail.
    However, these effort does not work well so far.

    Imagine that there are people who are these disabilities on 30km radios from
    nuke reactor.
    I heard that many disabilities die due to no help due to helper fear radiation from the reactor.
    Driver fear radiation, nurse also fear radiation, resident fear radiation.
    What mean that destroy community nearby the reactor.
    I realize that ALL people do BEST effort but these action cause another disaster sometime unfortunately.
    Therefore, I hope that do not too much concern ONLY NOW please for help many
    refugee on Japan.
    I also hope that many people who is no resident of Japan help Japan.
    I mean calm help and long term help.
    I believe that if you help so,we can back normal soon.

  • Comment number 21.

    I see the Earthwatch thread re Fukushima is now closed, even though it was one of the more active ones and the comments relevant.

    Anyone who lives within 1,000 miles of a reactor (everyone in the UK) will no doubt be very concerned about what happened at Fukushima, as a result of it losing its cooling arrangements. (The fact that this was initiated by an earthquake is not that relevant as the same could have stemmed from a plane crashing into the plant, enemy action, sabotage by a deranged worker, etc.)

    Can we please, BBC News, therefore have some facts for a change? (Not vox pops of people who end up crying on camera yet again, however understandable this might be).

    What we urgently need to know about the UK and EU plants is this:

    Do they, like Fukushima require active cooling for fuel ponds and shut-down reactors?

    If so do they have multiply redundant back-up systems to cover for all conceivable ways in which these could fail?

    Are these back-ups inspected, maintained and tested so that in the event of their being needed they spring into life as intended?

    Are the resullts of these inspections and tests transparent and in the public domain? If not why not?

    I note that since the disaster in Japan I have not heard one word of comparison, let alone reassurance re our installations on the BBC.

    I can only therefore conclude the truth might cause panic.

    Modern designs, not yet built are irrelevant. What is the state of the damned things we are stuck with for now?

  • Comment number 22.

    Questions111 is right, the issues of safety still have not been addressed. We keep hearing about cesium 131 and that it has a half life of 10 days. They can detect this one easily and attribute it to the Japan power plants because of its short half life.

    What about 137 which has also been released? It has a half life of 30 years! Humans and animals have evolved for millions of years and have adapted to naturally occurring radiation. Cesium 131, 137 etc are NOT the same. How can the body know what to do with these, they are different than natural radiation.

    Has strontium 90 been release? Another 30 half life and worse, it mimics calcium and is absorbed into bones. It isn't excreted it just sits there for 30 years spewing radiation. So there would be the potential of cancer to bone marrow cells.

    These reports, trying to reassure people are lacking of all the facts and seem like propaganda.


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