Radioactive Bricks Used in Tokyo

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    Back in May of 2010, Japan’s TBS network aired an investigative report about the sale and use of bricks that contain small amounts of radioactive uranium. Shortly after it was aired, somebody uploaded it to YouTube. Because the recent nuclear accident in Fukushima prefecture has heightened public interest in radiation safety, the video has been getting a lot of views in recent weeks. As the report is quite interesting, I’ve decided to post a partial summary of its contents.

    The video is divided into two parts (Part I and Part II). Embedding has been disabled, so this post will just contain screen captures:

    In front of the Ministry of Agriculture building in Tokyo, a reporter uses a gieger counter to measure radiation levels. Some bricks are giving off about 0.15 microsieverts per hour. They’re radioactive!!

    The bricks come from Ningyo-toge at the border of Okayama and Tottori prefectures, which was the center of Japan’s uranium mining operations in the 1950’s.

    Inside one of the Ningyo-toge mines, they measure the radiation of some uranium. It is 16 microsieverts per hour, meaning that one hour in that area would expose a person to the equivalent natural radiation exposure that most humans get in three days. Since visitors to the mine are only in the area for about 5 to 10 minutes, there is no reason to be worried about the low level radiation.

    The leftover dirt and rocks from mining contained small amounts of uranium. Until the Chernobyl accident, nobody really worried about the radiation from that soil, so it was just piled up outside. Since the late 1980’s, warning signs and barriers have been put up.

    Citizens groups wanted the soil stored in a safer place. After years of campaigning, they finally succeeded in winning a lawsuit in 2004. Authorities finally started to dispose of the soil. Of the 3,000 cubic meters of soil, 290 cubic meters of the most radioactive soil were sent to America for disposal. The remaining soil, which contained much lower levels of radiation, is being turned into bricks.

    The soil is mixed with cement to make bricks, which are then sold for about 90 yen each. Nobody has calculated the exact cost that goes into the production of each brick, but it seems very likely that they are being sold at a loss. Authorities carefully measure radiation levels, trying to make bricks that do not exceed readings of 0.22 microsieverts per hour.

    Authorities insist that the level of radiation in the bricks is not dangerous. The bricks are being sold to anyone who is interested. Some people are afraid to buy them. Others, such as the man in the above screen capture, don’t really think that the radiation is worth worrying about. He bought some of the bricks for his garden.

    Hundreds of thousands of bricks have been sold. About 430,000 have been used by the government and the nuclear industry. About 210,000 have been purchased by private businesses and individuals. Nobody is tracking the bricks, so they could be used almost anywhere.

    Professor Kiyonori Yamaoka of Okayama University is interviewed about the possible health risks of exposure to the bricks. He says that it hasn’t been proven that such low levels of radiation are dangerous, but one cannot be 100% sure about it. On the other hand, Professor Hiroaki Koide of Kyoto University (an anti-nuclear activist) thinks there is absolutely no “safe” level of radiation.

    While the journalists were working on this investigative report, they noticed a change on the homepage of the organization that was selling the bricks. In a section describing example uses of the bricks, it used to mention indoor gardens. They asked an official why that example had been removed, and if it meant that the bricks were unsafe for indoor use. The official didn’t give an exact reason why it was removed from the homepage, but said he believed that the bricks are still safe for indoor use.

    At the time this report aired, there were about 16,000 containers of soil that was apparently too radioactive to be made into bricks. Authorities were in the process of figuring out how to dispose of it.

    [hat tip to Ken Y-N]

    Side Note: It seems that most of these Japanese bricks are being used in outdoor gardens, where their direct contact with humans is somewhat limited. In the United States, some radioactive construction materials have been used in the interiors of major public buildings. The U.S. Capitol Building and Library of Congress are made of granite that contains uranium, emitting radiation 65 times higher than EPA safety limits. The dosage for the Capitol Building is about 0.85 millisieverts per year (0.097 microsieverts per hour).

    A few other radiation readings for your consideration:

    • Natural Background Radiation in Hong Kong: between 0.06 and 0.30 microsievert per hour.
    • Natural Background Radiation in Cornwall, U.K.: 0.251 microsievert per hour
    • Natural Background Radiation in Chennai, India: 3.42 microsievert per hour
    • “High” Level of Radiation in reported in Tokyo, Japan on March 16, 2011: 0.809 microsievert per hour
    • Radiation Level in Tokyo, Japan on April 29, 2011: 0.0677 microsievert per hour

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