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.

福島県の帰還困難区域に発生した山林火災は、浪江町と双葉町にわたって75ヘクタールを焼失。12日間燃え続けた後、5月10日に鎮火されました。

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.

この山林火災は放射能による健康被害の問題と、政府およびマスコミによる情報提供のあり方について様々な問題を提起しています。

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.

福島県は火災による放射性物質の拡散について、過小評価の態度を取り続けています。大手メディアは福島県庁のコメントを伝えるに過ぎません。例外であった紀伊民報（和歌山県）は5月2日付のコラムで、放射性物質の飛散について注意を促し、政府と全国紙が鈍感すぎる、と書いたところ、抗議と批判にさらされた末、１週間後に陳謝しています。

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.

しかし、大手メディアであれ、ソーシャル・メディアであれ、ニュースソースは一つしかありません。それは福島県が発表する環境放射線のモニタリング測定結果です。

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.

市民測定団体による測定結果が発表されるまでは、この測定結果が入手可能な唯一の測定値になります。しかし、この測定結果は単に測定値だけではなく、福島県のコメントがついて発表されます。ですので、測定値と評価と両者がセットで存在することになります。

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.

事実（ファクト）だけでなく、火災による健康被害の問題を矮小化、あるいは無視、否定する政府の態度を明らかにするには、この両者をあわせみることが必要です。健康被害の可能性が認められれば、住民を近辺に帰還できるようにする避難指示解除そのものが問題となります。これは政府、地方自治体の両者にとって、非常に不都合な事態になります。

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.

まずはどういうデーターがどういう風に提供されているか見ていきましょう。こういう状況の場合、まず見るべきは大気中の浮じんに含まれる放射性核種の測定結果です。火災発生後、福島県はすぐにそれに取り掛かっています。

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.

ところが、この一番肝心なデーターの前に空間線量率の測定結果が示されています。そして、そこには以下のコメントがついています。「火災前と比較して大きな変動はありません。」（下の図１、２と表１を参照）最初に出てくる変化なし、の評価は住民の皆さんの心配を鎮める大きいな効果があると思われ、メディアもこの「空間線量率に変化なし」のメッセージを伝えています。このコメントは最後の表に示されている大気中の浮じんの汚染レベルを隠してしまう作用を持っています。またこの表はグラフにすると明白な変化が見やすくなるのに、空間線量率と違ってグラフにはなっていません。

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).

しかし、内部被曝のリスクを伴う環境汚染がある場合には、空間線量率だけを見ていると大変な片手落ちになり、間違いに陥ります。空間線量率は外部被曝からの防護のためは有効ですが、放射線防護の観点からは、それだけでは不十分です。事実、東京電力では作業者の安全のために、まさにこの観点に立って空間線量率と環境汚染の両者をカバーする政策を取っています。この点については、このサイトの和英併記記事“Forest fire in the exclusion zone in Fukushima: Why monitoring the radiation dose is not enough for radioprotection”をご参照ください。特に記事に記載してある、東電作業者の放射線防護のための管理区域の区域区分の表をご覧ください。この表にある12区分は、シーベルト/時間であらわされる空間線量率のレベルと、ベクレルで表される（表面の場合はBq/cm2、空気の場合はBq/cm3）環境汚染密度/濃度のレベルの組み合わせで定義されています。

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.

以下の記述を読まれる時、この点を念頭に置いておいてください。また、測定されているのはセシウム134と137のみであり、内部被曝の検討に重要なアルファ線やベータ線を発するプルトニウムやストロンチウムなどのセシウム以外の放射性核種は測定されていないということも同様に念頭に置いておいてください。では、大気中の浮じんの測定値の変動（5月12日付の発表の３ページ）と火災地と調査地点図を見てみましょう。（同、４ページ）

３ページの表を見ると、３箇所の調査地点（５、６、７）で５月８日と１１日に測定値が上昇しているのがわかります。

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.

しかしながら、上に示したように、この表が現れるのは３ページ目であり、その前の１ページ目と２ページ目には変動のない測定値が紹介されています。前述の４つの表とグラフのうち、目立った変化が見られるのは最後の表だけです。そして、最後の表はグラフ化が省略されています。グラフにすると変化が顕著に明示されるからでしょうか？データーはその見せ方によって、人々の危機対応の仕方に影響を与えます。

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.

この測定結果について、福島県はなんとコメントしているでしょうか？以下は重複しているようで退屈かもしれませんが、福島県の放射性物質の２次拡散についての姿勢を確認するためですので、我慢してお付き合いください。

５月５日付のコメントから見て見ましょう。

太文字は強調のため翻訳者が太文字にしたものです。

“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.

(For information)

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″

(end quote)

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 ?

こうして文言の使い方を見てくると、福島県の姿勢は一貫して放射性物質の拡散を否定し、健康被害に言及しないことにあります。15.55mBq/m3まで数値が上昇しても、健康被害の可能性については何らの言及もありません。

最後の（参考）の箇所は林野火災に原因する内部被曝リスクが十分に小さいと、住民を安心させるコメントとして追加されています。では、本当にリスクがないのでしょうか？

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 ?

それでは、福島県のコメントと、そこからうかがわれる県の姿勢を問いただすために、以下の２つの点について見ていきたいと思います。

発表された測定値は火災以前の測定値と比べて憂慮しないといけないほど高い数値なのか、それとも無視できるくらいの上昇なのか？ 放射性物質は火災により舞い上がり、火災中、また火災以後、拡散する可能性があるのか？

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.

この２点について、２つのソースを参照させていただきます。最初の点については「ふくいち周辺環境放射線モニタリングプロジェクト」の小澤洋一さんのFBに5月10日に投稿されたコメント。２番目の点については、桐島瞬さんの5月14日付の週プレニュースに出版された記事です。

Yoichi Ozawa’s comments:

小澤洋一さんのコメント

フクシマ原発事故前の2010年文部科学省のセシウム137全国平均値は、0.00012 mBq/m3 です。

（訳者注:文部科学省平成23年12月、第５３回環境放射能調査研究成果論文抄録集、P20)

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).

今回の浪江町森林火災の 7.63 mBq/m3 は、63,583倍の数値です。

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.

もう一つ、北隣の南相馬市の「広報みなみそうま」の3月後半のデータでは、0.053 mBq/m3 が最大値で、0.021 mBq/m3が平均値とされています。この平均値でも、フクシマ原発事故前より100倍以上も高く、健康影響が心配されるレベルです。

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.

今回の浪江町森林火災の数値は、南相馬市の 10 ～ 100 倍のレベル、フクシマ原発事故前の 1,000 ～ 数万倍の汚染レベルを示しているものです。

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.

鎮火したから安全ということはありません。空気が乾燥すると放射性微粒子が舞い内部被ばくをします。更にこれらの数値は、セシウムのガンマ線しか計測していません。ベータ線やアルファ線を出す放射性核種も存在しており、これらによる内部被ばくが危険なのです。

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.

(end quote)

Now let’s have a look of the article of Kirishima on the possibility of the scattering of the radioactive materials.

次に放射性物質の拡散の可能性に関する、桐島さんの記事の抜粋をご紹介します。

Extract :

実際のところ、今回の山火事で放射性物質が飛散するリスクはなかったのだろうか？長崎大学大学院工学研究科教授の小川進教授は「セシウムは間違いなく飛んでいる」と話す。

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.”

「火災現場は人が住めないほどの汚染地帯。樹木の下にある枯れ葉や土壌にはセシウムが大量に吸着していたと思われます。そこで火災が起きれば、融点が摂氏２８度のセシウムは熱で気体になり、上空に舞い上がる。すると今度は上空で冷やされて粒子状になりながら花粉のごとく風に飛ばされ、その後、どこまで飛散するかは風向きと風速次第。強い西風が吹いていればそのまま太平洋まで飛んでいくでしょうが、弱い風なら近くの集落が汚染されてしまいます」

“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. “

また、早稲田大学理工学術院の大河内博教授はチェルノブイリ原発の例を挙げてこう指摘する。

In addition, Professor Hiroshi Okochi of the Waseda University Science and Engineering Institute points out the example of the Chernobyl nuclear power plant.

「２年前の２０１５年にはチェルノブイリ原発の周辺でも大規模火災が起きて、近くに置かれたモニタリングポストから基準値より１０倍高いセシウム１３７が検出されたことが知られています。詳しく調べてみないことにはわかりませんが、福島でも森林域には放射性物質が溜まっているため、飛散する可能性はあります」

“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.”

そう話す大河内教授らのグループは近々、福島県の火災現場周辺で調査を始めるという。大気中から舞い降りたダストを分析し、セシウムと一緒に植物が熱分解する際に生成されるレボブルコサンという粒子が含まれていれば、火災で飛散したことがわかるという。

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.

セシウムが飛んでいるとすると、懸念されるのは飛散エリアと人体への影響だ。

If the cesium is flying, the concern is how far it is dispersed and its effect on the human body.

福島県は「現場近くの測定で得られたセシウムのダスト量は最大でも１立法メートルあたり７．６３ミリベクレル。健康にほぼ影響はないレベル」（放射線管理室）という。ミリベクレルはベクレルの千分の一。微量だから心配いらないとのスタンスだ。そのため、周辺住民への対応も特にしないという。

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.

一方、前出の小川教授は３ヵ所の測定値だけで判断するのは危険だと指摘する。

On the other hand, Professor Ogawa points out that it is dangerous to judge only by the measurements of three monitoring emplacements.

「モニタリングポストの数値に変化がないから飛散していないという評価にしてもそうですが、ホットスポット的にセシウムが大量に降り注ぐ時間や場所がある可能性を考えると『被曝の心配がない』とは言い切れません。風下の住民は気をつけるべきです」

“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. “

福島県では奥羽山脈を超えて西から東へ強い風が吹くことも多い。十万山から北東方面に５キロ進んだところには避難指示が解除された浪江町エリアがあり、人が住んでいる。

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.

(end quote)

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.

こうして見てくると、火災以降の測定値は福島事故以前の34県の平均値と火災前の浪江町の北隣の南相馬市の平均値と比較して、極めて高い数値です。また、火災によってセシウムが飛散しているのはまず間違いないと考えられます。

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.

福島県の測定データー公表の仕方は空間線量率を意図的に強調し、大気中の浮じんの放射能汚染度の大幅な変動の事実を隠そうとしていると見受けられます。そこに含まれているメッセージは、シーベルトで表される空間線量率に変化がなければ、何も心配する必要がない、と言うものです。しかし、上に見たように、放射線防護のためにはベクレルで表される環境汚染も考慮に入れなくてはなりません。東電福島第一原発事故以来、原発は絶対事故を起こさないと言う安全神話は、内部被曝のリスクを隠し、ホットスポットやホットパーティクルの問題を消去してしまう、シーベルト神話とも言うべきものに取って代わられているように思われます。

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.

避難指示を解除し、そのようなリスクを伴うところに住民が帰還できるようにし、しかもリスクについて住民に情報を提供したり放射線防護の指示を与えていないというのは、到底正当化できる姿勢ではありません。住民を危険に晒す姿勢と言えるのではないでしょうか。

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Read more

Fire crews finally extinguish Fukushima blaze in no-go zone as officials battle radiation rumors, Japan Times, May 11, 2017

Taminokoe Shimbun 民の声新聞 (in Japanese), articles of May 2, 4, 8, 10, 12 and 16. The article of May 2 is published in our blog in English. (Wildfires in Namie, Fukushima 311 Voices, May 2, 2017)

Wildfires in Fukushima: reliable data or disinformation?, Fukushima 311 Voices, May 7, 2017

12日間もの長い間燃え続けた、福島県浪江町の山火事を巡る、報道と市民の態度について考えたこと (in Japanese), May 12, 2017