Blowing in the Wind

As winter approaches in the Tokyo area, I think of cold, dry wind blowing from the north. The temperature is usually slightly above zero, which means no snow cover on the ground. This is the perfect recipe for the re-volatization of cesium and other radionuclides that settled on the ground over the spring and summer. In addition, we have to think about the big unknown of how much cesium is going to be carried by cedar pollen that begins to appear in December and peaks in March.
In the part of northern Chiba prefecture where I live, local authorities told us that the fallout on the ground had been light and that there was no need to restrict activities. Yet a look at the history of fallout incidents puts the local situation in a different perspective:

1945 – 70
Cesium 137 deposition on USA from global nuclear weapons testing (in most places, some places were higher or lower)
2,000 ~ 6,000
Cesium 137 fallout on Japan from Chernobyl
Cesium 137 fallout on Japan from Asian dust storms that appear each spring
Cesium 134 and Cesium 137 deposition on Narita area of Chiba prefecture
10,000 ~ 30,000
Cesium 134 and Cesium 137 deposition on Fukushima
10,000 ~   3,000,000

Chernobyl designations (Cesium 137 Bq/m2):
weak: <37,000 - mitigation and decontamination, vigilance required
low: 37,000~185,000 - migration not necessary, restrictions and monitoring of food and water, mitigation and decontamination
high: 185,000~555,000 - migration allowed (even in normal circumstances Soviet citizens needed permits for internal migration)
heavy: 555,000~1,480,000 - restricted access, mandatory evacuation

No one can say for sure how our children will be affected many years in the future, but scientists are quite sure that as the fallout level increases, the number of cancer cases goes up from x per 10,000 to y per 10,000. Some of the increase in cancer rates in the US is sure to be due to the relatively low levels of weapons testing fallout, which, in the days before Chernobyl, were considered totally unacceptable. There is no reason to not worry just because the levels in the Tokyo area, by the Chernobyl scale, are called "weak." The chances of negative health effects have increased. It's all a gamble and a question of acceptable risk. The question is, as Dirty Harry would say, "Do you feel lucky, punk?" But the problem is that it is a question of adults deciding this question for the children.
During the winter it is common to see clouds of dust on the school grounds, and sports activities continue as they do in summer. My task now is to shake the local parents and school authorities out of their complacency and ask them if they want to take this gamble with their own lives and those of children, or if they want to play it safe by restricting outdoor activities. What's it going to be? The answer is blowing in the wind.

Notes on the table above

1. Cesium 137 deposition on USA from nuclear weapons testing
This amount is much lower than what we have in northern Chiba right now. Most scientific experts admit that this fallout increased the rate of cancer, although the link between fallout and cancer can never be proven in individual cases.
Cesium 137 deposition density due to global fallout. Institute for Energy and Environmental Research  http://www.ieer.org/offdocs/csdepglo.pdf

2. Cesium 137 fallout on Japan from Chernobyl
There was great shock and concern when the Chernobyl accident affected Japan in 1986, but in the present situation this figure of 99 Bq/m2 is something we would feel relieved to have .

3. Cesium in dust from Asia
In recent years, Japanese researchers have been concerned about radioactive particles that come to Japan in dust storms from the Asian continent. However, they found that the highest level recorded in one year was only 0.82 Bq/m2. Before the accident at Fukushima Dai-ichi, scientists thought that even this low number was something to be concerned about.
Data for 2 and 3 from:
Fujiwara, Hideshi. “Atmospheric deposition of radioactive Cesium 137 associated with dust events in East Asia.” Bulletin of the National Institute of Agro-Environmental Science, 85-115. 2010. Tsukuba, Japan. http://www.niaes.affrc.go.jp/sinfo/publish/bulletin/niaes27-2.pdf

4. Cesium 134 and Cesium 137 deposition on the Narita area
We can now see that the data for Chiba can be considered low only in comparison to the very serious contamination in Fukushima. We might be able to find safe food and water, but we have to worry now about dust on the ground entering the air again when the dry, windy weather of winter comes to us. We should also be concerned that governments have plans to burn contaminated sewage and waste. Governments claim they have effective filtering technology, but there has been no public disclosure about the effectiveness of electrostatic precipitators in trapping radionuclides in incinerators.

5. Cesium 134 and Cesium 137 deposition on Fukushima
Winter winds might also carry dust from places that are much more contaminated than Chiba. No one knows how much cesium will be carried in cedar pollen, for example.

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