The forest fires in the exclusion zone in Fukushima, near the crippled Fukushima Daiichi nuclear power plant (FDNPP), were extinguished on May 10 after having burnt 75 hectares in 12 days, spreading from Namie to Futaba.
The wildfires raised a number of questions about the radiation related health hazards and the ways the information was treated by the Fukushima prefectural government and the mass media.
Fukushima prefecture maintained the attitude of under-evaluating the possible impact of the fire in regard to the dispersion of radioactive substances. Major media transmitted the Fukushima government’s official comments, and an exceptional local newspaper, Kii Minpo (Wakayama prefecture), had to apologize after having received complaints and criticism for its column alerting the local population to the dispersion of radioactive substances by the fire, and saying that the government as well as the national newspapers are too dismissive of the radioactive dispersal problem.
However, when it comes to the news source, the only one on which mass media as well as social media can rely for the moment is the radiation measurement results published by Fukushima Prefecture.
Before the results of the measurements by civil groups come out, they are the only values we have. But then, these results are accompanied by comments of the Fukushima prefecture. So there are measurements, but there is also their evaluation.
We will go through both of them to shed light on the facts but also on the government’s attitude to minimize or even ignore or deny the health hazard risks related to this fire which, if recognized, would question the lifting of the evacuation order, which authorizes the return of the population in the neighboring areas. This questioning would be very inconvenient for both the central and the local governments.
The relevant data in this kind of situation is the measurement of radioactive nuclides contained in the dust in the air. This is precisely what Fukushima prefecture published right after the breakout of the fire.
Nonetheless, this information is preceded by the airborne radiation dose measurement with the comment: “there is no change in the radiation dose” (see Graph 1&2, Table 1 of the picture below). This has certainly a strong effect to ease the worry of the population, and most of the media transmit the message that “there is no change in the radiation dose.” This comment hides the fact of significant changes in the contamination levels in the dust in the air seen in the last table, which isn’t accompanied by a graph which would more clearly show the changes.
However, in the context of environmental radio-contamination, where the internal irradiation risk has to be taken into account, looking only at the airborne radiation dose can be fatally misleading, as it is only a measurement to decide if you need to protect yourself against external radiation. But even TEPCO itself established its workers’ radioprotection policy based on the view that both external and internal radiation protections are necessary. On this point, please see our article “Forest fire in the exclusion zone in Fukushima: Why monitoring the radiation dose is not enough for radioprotection”, and in particular the table showing 12 zones which necessitate corresponding radioprotection methods. The 12 zones are defined by the combination of the different levels of both airborne radiation dose, in Sieverts/time, and the environmental contamination density in Becquerels (surfaces: Bq/cm2 and air: Bq/cm3).
Keeping this in mind, and also the fact that only Cesium 134 and 137 have been measured, let’s look at the change of the values (see images below of Info May 12, page 3) as well as the map of the monitoring stations in relation to the fire site (idem, page 4, the site being the big red circle).
We clearly see the increase in measurement values at 3 stations (#5, 6, 7) on May 8 and May 11.
However, as we have mentioned above, this table appears in page 3, after the data in the pages 1 and 2 which show the stability of the values. Of the above 4 tables and graphs only the last table shows significant increases in radioactive dust in the air. And there is no graph for the last table. Is that because it would clearly show great changes? The way in which data are presented can influence how you respond to a crisis.
What are the comments of Fukushima prefecture accompanying the results? The following may be a tedious process, but please be patient so that you can judge for yourself the Fukushima government’s attitude toward secondary dispersal of radioactive elements, which is revealed through these comments.
We will start with the comments of May 5.
Bold letter format, for emphasis, was added by the translator.
“According to the measurement results of the survey meters near Mount Jyuman, the scene of the fire, no change has been noted compared to the result of the day before (table 1).
As for the airborne radiation dose measurements, no change has been noted compared to the measurements of before the fire (Graph 1).
The measurement results of the dust in the air near the Mount Jyuman were between ND and 1.97mBq/m3 (table 2). The measures of the Yasuragi so (Elderly people’s home Yasuragi) in Namie and those of Ishikuma Community Center increased, but as the data are still scarce, we will continue to monitor the change as well as that of the airborne radiation dose.
As for the measurement values of the dust in the air by the monitoring posts installed by the prefecture (Translator’s note: since before the fire), no change in values has been noted in relation to those of before the fire.”
Here is the comment of May 9.
“Since May 5 portable monitoring posts have been installed at three places near Mount Jyuman, the site of the fire, and we measure those daily. Their results as well as the measurement results of the pre-existing survey meters do not show any change compared to those of the day before (Graph 1, Table 1).
The results of the measurement of the airborne radiation dose by the monitoring posts installed near the fire scene since before the fire do not show any significant change compared to values of before the fire (Graph 2).
On the other hand, the results of the measurement of Cs 137 in the dust in the air near the Mount Jyuman are between 1.35 and 7.63mBq/m3. We are not able to judge the cause for the moment, but in addition to the penetration of the fire to the sedimentary layer of fallen leaves, which is the peculiarity of this wildfire, strong winds of the west which interfered with the operation of the helicopter, was observed throughout the day, so the influence of the upheaval of the dust and the incineration ash in the vicinity of the measurement point cannot be denied.”
Finally, the comment of May 12.
“Yesterday (May 11), the measurement results of the dust in the air were between 0.80 and 15.55mBq/m3. (The maximum value before was that of May 8: 7.63mBq/m3). We are not able to judge the cause for the moment. With these data and the coming results of the survey conducted by the Forestry Agency, we will evaluate the influence to the surrounding area, taking into account experts’ opinions. As for the dust monitor installed with the pre-existing monitoring post since before the fire, no difference in the measurements is noted.
The internal irradiation dose would be 0,0063 mSv/year if one inhales continuously the air containing 20mBq/m3 of Cs 137. This value corresponds to about 1/100 of 0,48 mSv/year* which is the internal irradiation dose due to the inhalation of radioactive substances existing in the natural environment. The value is sufficiently small.
*source: “The new edition of Daily Life Environmental Radiation (Radiation calculation of the national population) (Japan Nuclear Safety Research Association, December, 2011″
When we look at the wording, it is clear that the Fukushima prefecture consistently tries to deny the dispersion of radioactive materials and convey the information to minimize the risk of health damage without even mentionning the word “health”. With the quite spectacular increase to 15.55mBq/m3, no mention is made of a possible health hazard risk.
The last comment about the internal irradiation is added to reassure the population that there is minimal radiation risk due to the forest fires. Is this so ?
Let’s now look at two points to question these comments from the prefecture and the attitudes that they imply.
- Are the measurements significantly higher than those of before the fire ? Or is the increase insignificant?
- Are the radioactive substances in the ground likely to become airborne because of the fire and after the fire?
We will refer to two sources here. For the first point, we refer to the comments of M. Yoichi Ozawa of Fukuichi Area Environmental Radiation Monitoring Project, published in his FB page of May 10. For the second we will turn to the article by Shun Kirishima published in Syu Pre News on May 14.
According to the MEXT (Japanese Ministry of Education, Culture, Sports, Science and Technology), the average amount of Cs137 measured throughout Japan on 2010, that is to say before the accident of the FDNPP, was 0.00012 mBq/m3.
(Translator’s note: The report of the Ministry of Education, Culture, Sports, Science and Technology of 2010, Collection of articles of the 53rd research and study on the environmental radioactivity, p.20) (in Japanese).
The value of 7.63 mBq/m3 (Translator’s Note : the maximum value of May 8. The maximum value increased thereafter) measured this time during the forest fire in Namie is 63,583 times higher in relation to the above average value of the year 2010.
Another piece of data we can refer to comes from Kôhô Minamisoma (Newsletters from Minamisoma) which reports the measurement values of the dust in the air of the last two weeks of March 2017. Minamisoma city is located in the north of Namie. According to these data, the maximum value is 0.053 mBq/m3, and the average value is 0.021 mBq/m3. Even this average value is 100 times higher compared to the value of before the Fukushima Daiichi accident. This is already significantly high for health hazards.
The measurement values related to the forest fires in Namie are 10 – 100 times higher than the values of Minamisoma of March 2017, and several 10,000 times higher compared to those before the FDNPP accident.
The extinction of the fire does not mean that we are secure. When the air gets dry, the radioactive particles can become airborne and cause internal irradiation when ingested. Furthermore, the values cited above are only those of gamma rays of Cesium. We know that there are radioactive nuclides emitting alpha and beta rays. The internal irradiation of these radioactive nuclides is very dangerous.
Now let’s have a look of the article of Kirishima on the possibility of the scattering of the radioactive materials.
In fact, was there no risk of radioactive material scattering with this wildfire? Professor Susumu Ogawa of the Nagasaki University Graduate School of Engineering says, “Cesium is definitely flying.”
“The fire site is such a contaminated area that people cannot live there. It seems that the leaves and soils under the trees were absorbed in large quantities of cesium. If there is a fire, since the melting point of cesium is 28°C, it becomes a gas by heat, and it is dispersed in the sky. Then, it is cooled and is blown in the wind like pollen while becoming a particle shape. How far it scatters after that depends on the wind speed and direction. If a strong west wind blows, it will fly to the Pacific Ocean, but the nearby settlements will be contaminated if the wind is weaker. “
In addition, Professor Hiroshi Okochi of the Waseda University Science and Engineering Institute points out the example of the Chernobyl nuclear power plant.
“Two years ago, in 2015, a large-scale fire occurred in the vicinity of the Chernobyl nuclear plant, and it is known that Cesium 137 was detected 10 times more than the reference value from the nearby monitoring post. Similarly, though we cannot know exactly before an investigation, there is the possibility of the scattering of radioactive materials in the forest areas in Fukushima also.”
Professor Okochi’s research group will begin an investigation near the fire site in Fukushima prefecture soon. It can be verified that radioactive scattering has occurred if the analysis of the dust taken from the air shows that it contains a particle named levoglucosan, which is generated when the plant is thermally decomposed with Cesium.
If the cesium is flying, the concern is how far it is dispersed and its effect on the human body.
According to the Fukushima prefecture, “the amount of cesium dust obtained by the measurement near the site is up to 7.63mBq/m3. This is a level that has almost no effect on health (Radiation management section)”. A milli Bq is 1/1000 of a Bq. The Prefecture’s stance is that there is no need to worry because it is a negligible amount. This implies that the Fukushima prefectural government would not take any particular action nor caution the surrounding residents.
On the other hand, Professor Ogawa points out that it is dangerous to judge only by the measurements of three monitoring emplacements.
“We cannot say definitely that ‘there is no fear of irradiation’, when we consider that a great amount of cesium can pour into a small place in a short period of time, as in the case of a hotspot. The same can be said for the evaluation saying that there is no scattering because there is no change in the values of the monitoring post. People living downwind should be careful. “
A strong wind blows often from the west to the east in Fukushima prefecture blowing over the Ohu mountain range. At five kilometers to the northeast from Mount Jyuman, there are areas in Namie where the evacuation orders were lifted, and people are living there.
So the measurements that are known already at this point are much higher compared to the values of the average of 34 prefectures before the nuclear accident, or those of the vicinity before the fires, and it is very probable that cesium is scattered by the fire.
The way that Fukushima prefecture presents the measurement data deliberately emphasizes the airborne radiation dose and its stability, hiding the fact that the measurements of radioactive dust in the air show strong variation. It also conveys the implicit message that if the airborne radiation dose is stable, in terms of Sieverts, there is no need to worry. However, as we have seen above, we have to take into account the environmental contamination also measured in terms of Bequerels. Since the FDNPP accident, the myth of security (that there can’t be any accident) seems to be replaced by a myth of Sieverts, which hides the risk of internal irradiation, while erasing the problems of hotspots and hot particles in the air.
Opening the area for its population to return to be exposed to such risks and furthermore without informing them about the risks and the measures to protect themselves can hardly be justified. It can be endangering many people.
Fire crews finally extinguish Fukushima blaze in no-go zone as officials battle radiation rumors, Japan Times, May 11, 2017
Wildfires in Fukushima: reliable data or disinformation?, Fukushima 311 Voices, May 7, 2017