Tokyo-based citizen radiation monitoring group Safecast published a map of radiation levels in Kyoto city. The map includes areas such as the Kyoto incinerator plant, where radioactive waste could be incinerated if Hosono got his way in spite of local opposition; Kyoto JR train station; popular tourist spots such as the park of the imperial palace;  nearby farming village Ohara, etc. It was “safecast” by a bicyclist at 1 meter above ground level yesterday. To our knowledge, this is the first map in Japan made in the monitored land as Safecast understandably focus on radiation levels in the no man’s land. Hopefully other cities such as Osaka, Fukuoka, etc. as well as nuclear plants such as repetitively troubled Monju will follow.

Levels are within 35 to 70 CPM (count per minute), i.e. between about 1 to 2 mS/year. Although these levels are twice as expected, they are harmless even for residents, therefore all the more for short-stay visitors. A screenshot of the map is reproduced below.

Levels could help give an indication as to the trustworthiness of government data. Asahi News reported that the official read-out for nearby Osaka was 18.9 becquerels per square meter (Cf. Analysis Of Japanese Government Radiation Spread Report on SurvivalJapan). I found a conversion formula widespread on the Internet however I could not verify it from a trustworthy scientific source so please use caution with the following comparison: 1 Bq/cm2 would be equivalent to a 1.319 uSv/h skin exposure dose – in other words, 1 Bq/m2 to 0.0001319 uSv/h (using non-scientific notation on purpose). Hence the density in Osaka would correspond to an equivalent dose of 0.0025 uSv/h. Since the natural background radiation is at sea level typically around 0.05 uSv/h (or 380 Bq/m2), it seems that there is something wrong either with the formula or with official data – or more likely both. According to the same article / report: “The smallest figure of 0.378 becquerel per square meter came from Uto, Kumamoto Prefecture.” – if the formula was right, since this is a thousand times less than the natural background radiation, it would prove to be a ludicrous statement. Another possibility would be that the reporter has got his units mixed up, as this was often the case in first news reports after March 11 (hopefully I am not the one mistaken here). However, in that case, revised upward with a factor 1000, the value of Tokyo would be 17,354 MBq/m2, which is equally absurd. In fact, since Becquerel is the unit for the number of disintegration per second, it could be transposed in uGy/h through the CPM rate, Geiger sensor surface, etc. – that is the formula would be different for each Geiger counter as opposed to a universal one. Indeed, notwithstanding that it is not an authoritative source by any means, Wikipedia article about Becquerel does mention the following, in the paragraph titled “Bq versus counts per second”:

“When measuring radioactivity of a sample with a detector, a unit of “counts per second” (cps) or “counts per minute” (cpm) is often used. Some radiation detectors are calibrated in “disintegrations per second” or “decays per second.” All of these units can be converted to the absolute activity of the sample in Bq if one applies a number of significant conversions that take into account the radiation background, the detector efficiency, the counting geometry, the sample size, and the self-absorption of the radiation by the sample.”

Clearly if the relationship between Becquerel and CPS is specific to so many factors, then the formula ought to be a false meme carried by Internet. Sadly, I first encountered it on a blog titled “Education Japan” by “Sean Marsula in Iwate”. Fortunately, comments by readers show that the aforementioned blog is a dangerous fraud, at least when it comes to providing education about radiation, which is exemplified by the blogger’s replies, for instance on April 5th (sic):

“The basic conclusion is that radiaton/radioactivity from Fukushima is essentially certain to have no effect on human health in Tokyo, and if there were any bad consequences, they would be *much* smaller than many other factors (e.g., air pollution, diet, second hand smoke) that affect health.” – heritageofjapan (sic) aka Aileen Kawagoe ?

One of our Kyoto sources who sent 3 local soil samples for analysis reported that Cesium-134 had not been detected whereas “some” Cesium-137 had. We agreed that since the half-life of Cesium-134 is 2 years, there should be some included too if the radioactivity had come only from Fukushima (Cesium-137 half-life is 30 years). My source could check that the levels of radioactivity under his/her house was the same as outdoors, further implying that radioactivity dated from before its construction. Some possible explanations are:

– Fall-out from nuclear bomb tests – yet explosions in the Bikini Atoll (Pacific Proving Grounds) or in Xinjiang, China (Lop Nur nuclear weapons test base near Malan) are equally remote from Japan (at least 3,000 miles). Hawaii is in fact much closer to Bikini.

– Fall-out from Hiroshima and Nagasaki. Hiroshima is less than 200 miles from Kyoto and Eastern winds could easily have carried the fall-out along the southern coast of Honshu (Okayama, Kobe, Osaka, Nara and Kyoto) given the terrain relief.

– Recurrent nuclear power plant incidents in Honshu, some after failed cover-ups by JAPC, as along the so-called “Nuclear Ginza” (Monju, Tsuruga both had radiation leaks and are only 50 miles away from Kyoto; Shika where a criticality incident occurred in 1999 is 150 miles away from it). Some events were probably never uncovered.

Proximity in time and space, i.e. Nuclear Ginza, is probably the most influental factor in the overall contribution of radioactive sources. It should be noted that levels remain very low in all cases and that any city in the world close to a normally functioning nuclear power plant or under the fall-out of nuclear weapon testings would probably present the same or higher radioactivity levels. Central Idaho, for instance, is affected with the highest per capita thyroid dose in the US in the wake of Nevada testings according to the following Wikimedia Commons map (source: US National Cancer Institute). Although this may seem slightly off-topic for a post about Kyoto, Japan, it serves as a relative reference point in our nuclear age and hence carries full relevance in a country from where some might be tempted to run away for lack of a bigger picture.

Because of concerns about worldwide fallout levels, the Partial Test Ban Treaty was signed in 1963. Above are the per capita thyroid doses (in rads) in the continental United States resulting from all exposure routes from all atmospheric nuclear tests conducted at the Nevada Test Site from 1951-1962.

  1. In response to your comments, first of all, you fail to note that the blog post to which you refer was made in the early days March 26th before much data was available and before any of the information on how Tokyo has been affected by the downwind factors, or before the cesium maps became available. Or long before anyone knew strontium or plutonium could travel so far. 2nd, you have taken my statement out of context, it was directly in relation to the information that was available at the time to any of us, and at the time it was not known that Tokyo was in the path of the downwind. 3rd, the post was a collation of various commentators, I cannot comment on Sean Marsula’s calculations as I did not make those, but the detailed calculations and formulations are open for all to see, and Sean invited others to look over those and to comment on the calculations and was willing to stand to be corrected. The post represented the sum of views being put forward and explored at an early point in time as the crisis was unfolding itself and progressing. Fourth, we have consistently followed the situation since then and have revised our position with regular spot updates since then. If you have followed us at all, you would know we have published every cesium fallout map, official as well as citizen’s maps, scientists’ projections in every spot date that we’ve carried since then. We have also since then reviewed as much of the Russian as well as European cancer research, heart disease research in conjunction with Chernobyl as well as nuclear testing and fallout as we could find and have discussed all of these on our offline EIJ forum and it should be clear to our readers that our position on food and health safety has since changed a lot. We have since the date of the post in question noted all of the hot spot news, breaches of food limits from official as well as Greenpeace/NGO sources, food safety concerns. We have even gone to some lengths to look at the means to protect ourselves with an article “Countering radiation damage and contamination: Anticancer cures, quick detoxes or quackeries?” The blog shows the progression of our evolving discussions, explorations and discovery process and desire to look at all data and information from all sources, while noting the possible bias of any camp. It would be helpful to the efforts to facilitate the nature of debate and discourse that we have been trying to carry out on our forum, if you reported on our writings with more equilibrium, instead of picking up quotes out of context like many charlatan journalists are wont to do and labeling us as “dangerous”. It represented a position taken at a specific point of time, in view of what was known to us at the time. Anyone following our blog knows there is no where else on the internet since the disaster happened, where Fukushima news as been followed as keenly as our forum, nor ever bit of data or news scrutinized in as great detail or in its entirety and without slant…as opposed to mere snippets/quotes out of context in support of one’s own biased viewpoints.

    • Thank you for your quick feedback. The issue with your blog post is the disinformation and educational disservice it provides, especially given your stated mission to ″Educate Japan″. The tone of the whole post is reflected in its passive aggressive and biased comments. The date has been duely noted as you can see if you read us better. It was obvious to many, including your commenters and this blogger, that the situation was not as you claimed, and your views put you on par with TEPCO, as one of them commented. My criticism stands and is not taken out of context for this damaging page, you put your audience at risk back then. Since you have apparently some influence on a community of parents in your area, it is even criminal. I didn’t check other posts as this one made for the perfect example of an ignorant and dangerous blog. Since your attitude back then to a commenter and now to me in face of this criticism remain the same, i.e. defensive aggressive, it seals the debate and harms your blog credibility.

      About the false formula, for all I know, your blog may well be the source of its widespread dissemination on the Internet, so you would have some beneficial action on the community if you updated the post by mentioning proeminently that it’s false and where exactly Sean got it from.

  2. Sean says:

    Hi. Sorry I’m a little late to the party but just wanted to clarify my calculations. You’ll notice there was a Microsoft Word document attached to the post for my quote taken from the Japan parenting mailing list “Education-in-Japan”. Most of the numbers come from common conversions. I believe the 36,000MBq was from a number that was a topic of discussion or that I was curious about:

    “1 MBq = 1,000,000 Bq
    1 km2 = 10,000,000,000 cm2

    36,000 MBq 1,000,000 Bq 1 km2
     km2 1 MBq 10,000,000,000 cm2

    = 3.6 Bq/cm2

    1 Bq/cm2 = 1319 nGy/hr

    3.6 Bq/cm2 1319 nGy/hr
    1 Bq/cm2
    = 4748 nGy/hr

    1 μGy = 1,000 nGy

    4748 nGy 1 μGy
    h 1,000 nGy
    = 4.748 μGy / h

    1μGy = 1μSv

    So, 4.748 microsieverts per hour (μSv/hr) “ (End quote)

    All of these conversion factors are easily verifiable on the Internet or with basic math. The one exception is “1Bq/cm2 = 1319 nGy/hr”, which I took from the National Institute of Radiological Science ( I could not verify this with another English source (it is cited by other Japanese language sources) at that time so I posted my conversions to the list for discussion.

  3. Sean says:

    First of all, I commend you on your general objectives with respect to this blog. Nuclear science is tricky to navigate and a field still riddled with unsolved questions. I think the hyperbole you used with respect to Ms. Kawagoe’s blog is misplaced. As you indicated about yourself in the early days following the incident at Fukushima, many of us on the mailing list also believed things to be relatively safe given an appropriate distance. This blog post taken from March 26, 2011, with comments from mailing list members likely several days before that, displays our early attempts as concerned parents to work out the science as best we could given the data (or lack thereof) at the time. I realize you like many of us are pressed for time in researching these things, but for you and readers coming to this post I’d like them to be aware that, as Ms. Kawagoe has also pointed out, the blog has evolved and highlighted the potential dangers, misconceptions, and misinformation regarding radiation and the health consequences through citations of news and scientific sources. A read through the medical literature points mostly to inconclusive results on both sides – low-dose radiation cannot definitively be declared dangerous nor safe. We can only sift through the mountains of information coming at us from news organizations and others and interpret that, as you are also doing. So, I’d like all to be aware that this mailing list is an excellent avenue for parents remaining here to get and discuss the information.

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