Tokyo Radiation Levels
Mar 17, 2011 | 52 Comments | 142,154 views

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Due to concerns about radiation in Tokyo from a number of our readers, Metropolis will publish frequent radiation levels (sometimes multiple times daily if relevant). This is a log of background radiation levels in Tokyo from March 15 2011. Measurements will be taken daily at different times. Levels are measured in micro-Roentgens and micro-Sieverts using using a Polimaster PM1703M Scintillator and S.E International Radalert 100 Geiger counter respectively.

We’ve added a Twitter feed for those twitters out there: http://twitter.com/#!/TokyoRadLevels

2011-05-31 9:14: 0.166 micro-Sieverts/h on Geiger counter (α, β & γ). 11 micro-Roentgens/h (0.11 μSv/h) (γ). Location: Roppongi Hills. Minato-ku, Tokyo. Weather: overcast, winds from the east. Safe.

‎2011-05-23 14:31: 0.186 micro-Sieverts/h on Geiger counter (α, β & γ). 11 micro-Roentgens/h (γ), (~11 cpm). Location: Roppongi Hills. Minato-ku, Tokyo. Weather: overcast, winds from the east. Safe.

2011-05-24 18:00: 0.135 micro-Sieverts/h on Geiger counter (α, β & γ). 8 micro-Roentgens/h (γ), (~8 cpm). Location: Roof of Metropolis office, Minato-ku, Tokyo. Weather: overcast, wind from the east. Safe.

2011-05-23 12:39: 0.166 micro-Sieverts/h on Geiger counter (α, β & γ). 11 micro-Roentgens/h (γ), (~11 cpm). Location: Roppongi Hills. Minato-ku, Tokyo. Weather: rainy, winds from the north. Safe.

‎2011-05-22 13:29: 0.166 micro-Sieverts/h on Geiger counter (α, β & γ). 9 micro-Roentgens/h (γ), (~11 cpm). Location: Inokashira koen (park), Kichijoji. Weather: Partly cloudy, winds from the north. Safe.

‎2011-05-22 12:17: 0.176 micro-Sieverts/h on Geiger counter (α, β & γ). 11 micro-Roentgens/h (γ), (~11 cpm). Location: Shimokitazawa. Weather: Partly cloudy, winds from the north. Safe.

2011-05-22 9:41: 16 micro-Roentgens/h (γ), (~16 cpm). 0.249 micro-Sieverts/h on Geiger counter (α, β & γ). Location: Kita-ku, Tokyo. Weather: clear, winds from the south. Safe.

2011-05-16 12:43: 8 micro-Roentgens/h (γ), (~8 cpm). 0.114 micro-Sieverts/h on Geiger counter (α, β & γ). Location: Roof of Metropolis office, Minato-ku. Weather: cloudy, winds from the south west. Safe.

‎2011-05-15 12:00: 14μR/h scintillator (γ). 0.166 micro-Sieverts/h on Geiger counter (α, β & γ). Location: Kawama, Noda city in Chiba. Safe.

2011-05-14 17:04: 18 micro-Roentgens/h (γ), (~18 cpm). 0.290 micro-Sieverts/h on Geiger counter (α, β & γ). Location: Ueno Koen (park), Tokyo. Weather: small storm, winds from the south. Safe.

‎2011-05-14 9:38: 16 micro-Roentgens/h (γ), (~16 cpm). 0.259 micro-Sieverts/h on Geiger counter (α, β & γ). Location: Kita-ku, Tokyo. Weather: clear, winds from the north. Safe.

2011-05-11 13:12: 12 micro-Roentgens/h (γ), (~12 cpm). 0.135 micro-Sieverts/h on Geiger counter (α, β & γ). Location: Roppongi Hills. Minato-ku, Tokyo. Weather: rain, winds from the south. Safe.

2011-05-09 9:03: 12 micro-Roentgens/h (γ), (~12 cpm). 0.155 micro-Sieverts/h on Geiger counter (α, β & γ). Location: Roppongi Hills. Minato-ku, Tokyo. Weather: clear, winds from the north. Safe.

‎2011-05-01 11:25: 13 micro-Roentgens/h (γ), (~13 cpm). 0.207 micro-Sieverts/h on Geiger counter (α, β & γ). Location: Cement park in Nishi-Ikebukuro, Toshima-ku, Tokyo. Weather: Overcast with rain, winds from the south. Safe.

‎2011-04-30 12:32: 17 micro-Roentgens/h (γ), (~18 cpm). 0.228 micro-Sieverts/h on Geiger counter (α, β & γ). Location: Kita-ku, Tokyo. Weather: clear, winds from the south. Safe.

2011-04-27 8:59: 14 micro-Roentgens/h (γ), (~8 cpm). 0.207 micro-Sieverts/h on Geiger counter (α, β & γ). Location: Aoyama Cemetery, Minato-ku. Weather: partly cloudy, winds from the south. Safe.

2011-04-25 9:06: 13 micro-Roentgens/h (γ), (~13 cpm). 0.197 micro-Sieverts/h on Geiger counter (α, β & γ). Location: Roppongi Hills, Minato-ku. Weather: clear, winds from the north. Safe.

Full history of readings

2011-03-15 08:30: 9 micro roentgens/h (9-10 micro R = normal baseline). Normal

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*sorry for the mixing units. From now on, daily readings in both micro roentgen and micro sieverts.

What does this compare too?

1 Sievert for 1 hour will kill 50% of people exposed. This is a deadly

0.4 Sieverts (400 milli sieverts) per hour = conditions in the Fukushima Daiichi plant. 2 hours at this level will burn skin like a sunburn and produce nausea and radiation sickness.

0.05 Sieverts (50 milli Sieverts) per hour = maximum allowed exposure by personnel working in nuclear facilities.

0.014 Sieverts (14 milli Sieverts) per hour = about a chest CT scan. 6–18 mSv is the range for a medical chest CT scan.

0.0002 Sieverts (0.2 milli Sieverts) per hour = 1 arm X-ray equivalent per hour. 50 hours at this would roughly equal your years dose of radiation.

0.0000002 Sieverts (0.2 micro Sieverts) per hour = Average normal background radiation for most cities in the world. 0.2 micro sieverts = 2 / 10,000,000 sievert or 2,000,000 times below deadly dose. 40,000 time below maximum allowed dose.

0.00000014 Sieverts (0.14 micro Sieverts) per hour = Tokyo background radiation on March 17th 2011, 6 days after the earthquake and nuclear plant crisis.

0.0000001 Sieverts (0.1 micro Sieverts) per hour = eating 1 banana per hour.

What do the units mean?

Roentgens are measure of the amount of radiation required to liberate charge of one electrostatic unit of charge (esu) in 1 cm³ of dry air at standard temperature and pressure. It’s a useful unit for legacy reasons because many people understand the Roentgen unit and the dose equivalent; Roentgen Equivalent Man (rem).

Sieverts are the biological dose. 1 Sievert = 1 Joule per Kilogram. Or the (damaging) energy imparted on the body by ionizing (nuclear) radiation.

*Disclaimer: We are not qualified experts in the field of nuclear science and nuclear medicine. Metropolis owns a Geiger counter and we are just giving a daily reading of exactly what we see on the screen of the Geiger counter. Geiger counter readings are taken outside, in an open area after the device has had 2 minutes to get an average reading of the background radiation level.

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52 Comments

  1. Kim | May 24, 2011 at 6:10 pm

    Thanks Metro for doing this!
    tgilbert, now that you have your own equipment, I hope you will be kind enough to share your findings with the rest of us.

  2. Eivan | May 25, 2011 at 3:12 pm

    @Metro, don’t worry about “tgilbert” – the service you have provided here, has been completely reasonable. You otherwise have provided additional, more frequently updated links and that is perfectly acceptable. It’s safe to say that the average levels in and around Tokyo, are at a point where it’s not higher or more dangerous than the average background radiation levels in other cities around the globe. Anyone with ‘real’ credentials would not spout off such as ‘tgilbert’ has. If his education and experience was true in nature, he would have known to seek a more complete, academic or scientific resource other than a social English-based magazine’s website. Not to discredit your sharing of knowledge, I’m only kindly pointing out that persons educated in the sciences should be resourceful enough to engage more complete and universal data.

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