This page to help people get information on the current issues of Tokyo tap water. Most of the information is provided by Ministry of education, culture, sport, science and technology Japan (MEXT).
Recently it was reported that at a water purification plant in Tokyo, levels of radioactive Iodine-131 was detect in the water at levels over 2 times considered unsafe for infants. The water is since returned to a state considered safe. The water was not radioactive, it just contained high (but still minute) levels of Iodine-131 and Caesium-137 which themselves are radioactive.
*Note, There is a 24 hour delay in the information due to the testing process.
Latest information:
| Date | Iodine-131 (Bq/kg) | Caesium-137 (Bq/kg) |
| 2011/05/14 | Not Detected | Not Detected |
| 2011/05/13 | Not Detected | Not Detected |
| 2011/05/12 | Not Detected | Not Detected |
| 2011/05/11 | Not Detected | Not Detected |
| 2011/05/10 | Not Detected | Not Detected |
| 2011/05/09 | Not Detected | Not Detected |
| 2011/05/08 | Not Detected | Not Detected |
| 2011/05/07 | Not Detected | Not Detected |
| 2011/05/06 | Not Detected | Not Detected |
| 2011/05/05 | Not Detected | Not Detected |
| 2011/05/04 | Not Detected | Not Detected |
| 2011/05/03 | 0.1 | Not Detected |
| 2011/05/02 | Not Detected | Not Detected |
| 2011/05/01 | 0.1 | Not Detected |
| 2011/04/24 | 0.36 | Not Detected |
| 2011/04/23 | 0.3 | 0.2 |
| 2011/04/22 | 0.36 | 0.41 |
| 2011/04/21 | 0.26 | Not Detected |
| 2011/04/20 | 0.19 | Not Detected |
| 2011/04/19 | 0.29 | Not Detected |
| 2011/04/18 | 0.22 | Not Detected |
| 2011/04/17 | 0.2 | Not Detected |
| 2011/04/16 | 0.3 | Not Detected |
| 2011/04/15 | 0.3 | Not Detected |
| 2011/04/14 | 0.41 | Not Detected |
| 2011/04/13 | 0.41 | 0.26 |
| 2011/04/12 | 0.57 | Not Detected |
| 2011/04/11 | 0.6 | 0.26 |
| 2011/04/10 | 0.71 | Not Detected |
| 2011/04/09 | 1.0 | 0.26 |
| 2011/04/08 | 0.89 | 0.48 |
| 2011/04/07 | 1.4 | 0.6 |
| 2011/04/06 | 1.63 | 0.5 |
| 2011/04/05 | 2.6 | 0.64 |
| 2011/04/04 | 3.82 | 0.591 |
| 2011/04/03 | 2.93 | 0.501 |
| 2011/04/02 | 2.0 | 0.45 |
| 2011/04/01 | 2.1 | 0.45 |
| 2011/03/31 | 3.4 | 0.88 |
| 2011/03/30 | 5.1 | 0.9 |
| 2011/03/29 | 5.6 | 0.51 |
| 2011/03/28 | 9.8 | 0.82 |
| 2011/03/27 | 20 | 1.2 |
| 2011/03/26 | 37 | 1.8 |
| 2011/03/25 | 32 | 2.1 |
| 2011/03/24 | 25.6 | 2.4 |
| 2011/03/23 | 26 | 1.5 |
| 2011/03/22 | 19 | 0.13 |
Japan’s maximum allowable concentrations are:
- 300 Bq/kg of Iodine-131.
- 200 Bq/kg of Caesium-137.
- (100 Bq/kg I-131 & 30 Bq/kg Cs-137 for Infants).
For comparison the IAEA and WHO maximum allowance guidelines are 3000 Bq/kg I-131and and 2000 Bq/kg Cs-137.
The units Bq/kg = Becquerel’s a kilogram (1 liter of water ~= 1kg of water).
A Becquerel = 1 decay (ionizing radiation emission) per second. 10 Bq/kg means that 10 atoms are decaying and giving off radiation each second. There are about 3.3428×10^25 molecules of water in a liter (~33,428,000,000,000,000,000,000,000 molecules).
More information about:
Information comes from this source:
Tokyo (English): http://mextrad.blob.core.windows.net/page/13_Tokyo_en.html
東京 (日本語): http://mextrad.blob.core.windows.net/page/13_Tokyo.html
All Areas (English): Discontinued by MEXT.
All Areas (日本語): http://www.mext.go.jp/
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4 Comments
Hello – just wondering if this sample / test is done in a few different locations ? Is it really scientific? What was the value before the disaster, was it zero?
I believe this is sampled at Shinjuku. It’s scientific but released by the Ministry of Science. Would the government lie? Maybe. Would Scientist? Probably not. Ruin their credibility for life. I think it’s safe to say it’s scientific. The level before the disaster would be “Not Detected” (basically 0) because you really only get those 2 elements from nuclear fission.
I’m so worried that the tap water might not safe for driking, I can’t find any available water on vending machines and convenient stores, all were sold out..
Anyway, thanks for the information, now I can drink my tap water again.. woohooo.. Banzai!!
I wonder how this compares with the levels of Chernobyl. Didn’t Japan back then ban all Soviet imports? What were the regulations then?