Radiation visualizations paint a different picture of Japan

Radiation data collected in Japan contradicts some media reports.

This piece was originally posted on The Daily ACK. Updated visualisations are now available with data spanning from 17:00 16th March – 17:00 20th March.

Over the weekend I came across some data on levels of radiation in Japan collected by the Japanese government, and helpfully translated into English by volunteers.

The data was somewhat stuck in PDF format. However, Gemma Hobson, Pete Warden, and I transcribed, mostly by hand, some of the more helpfully formatted files into CSV format (16KB) making it acceptable for Pete’s OpenHeatMap service. The map embedded below shows our first results.


Environmental Radioactivity Measurement, 17:00 16th March – 17:00 18th March —
For data from the Fukushima site itself see the “Readings at Monitoring Post out of 20 Km Zone of Fukushima” data sets online. Data collection from Mlyagi (Sendai) ceases at 17:00 on the 17th of March and does not resume. Several other smaller duration data drop outs also occur during the monitored period.

As you can see from the visualisation, environmental radiational levels change fairly minimally over the time course of the day. Most measurements are steady, and within the historic ranges, except around the troubled Fukushima plant where readings are about double normal levels.

Things become more interesting however when we look at the historic baseline data. The two maps below show the typical range of background environmental radiation in Japan. The first shows typical minimum values, while the second shows typical maximum values. Put together they illustrate the observed range for environmental radiation across Japan.

Finally, the map embedded below shows the environmental radioactivity measurements with respect to the typical maximum values for that locale. From this visualisation it is evident that the measured values throughout Japan are normal except in the immediate area surrounding the Fukushima reactors, where levels are about double normal maximum levels.

Environmental Radioactivity Measurement, Ratio with respect to typical Maximum Values

When analysing this data you should bear in mind that the normal environmental range in that area is actually fairly low compared to other areas in Japan. Currently the levels of radiation at the plant boundary are actually still lower than the typical background levels in some other parts of the country. Levels also seem fairly static over time, and do not seem to be increasing as the situation progresses.

Unless the situation significantly worsens, which admittedly is always possible, human habitation in close proximity to the plant will not be affected in the medium term. From talking to people on the ground in Japan, and by looking at the actual measurements across the country, a very different picture seems to be emerging than that reported by the Western media. Some of those media reports seems highly skewed, and heavily politicised, by comparison.

I think everyone should take a deep breath and look at the evidence, which is suggesting this is not another Chernobyl in the making. It may not even be another Three Mile Island. If the remaining functioning reactor units are decommissioned following this incident it may well have more to do with politics than the science.

With thanks to Pete Warden and Gemma Hobson.

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