Kinda bad news for the hassaku

Posted on June 28, 2011


Ideas about Edoble had been floating around all winter. The hassaku are most prominent in the drabbest season of the year. Back before March 11, my concerns about foraging in Tokyo had mainly to do with laws, cultural taboos, and the possibility that the urban soil isn’t the most pristine and so fruits harvested by the side of a busy road might be contaminated with exhaust fumes or something. Oh how quickly things can change. While still dealing with the shock of the earthquake and starting to learn of the horror of the tsunami, it became clear that there was also a nuclear situation going on which would affect many things, including the edibility of things grown outside. Early in spring, I got lots of people’s opinions on the safety of growing things on the balcony and nearly everyone didn’t show concern. Also, garden centers were selling all sorts of fruit and vegetable plants for the gardening season. Surely they wouldn’t be doing good business if it weren’t OK for people in Tokyo to eat things grown in their gardens. So, I put my concerns aside. They’ve now been piqued again, but only very slightly, and now I’ll explain why.

Last Friday, I went to a talk given at Tokyo Hacker Space about the use of Geiger counters. The event was conducted by several members of the group Safecast which is a collection of volunteers who are mapping radiation levels in Fukushima and other areas in eastern Japan, and are also distributing Geiger counters and teaching people how to use them and contribute to the task of mapping. The audience was briefed on the complicated task of detecting radiation. It really depends on the tool being used, whether it is calibrated to measure alpha, beta, or gamma radiation, and on what is being measured, for example, the surface of a play ground or food to be ingested. I wont recite all the jargon here, but do recommend checking out Safecast’s next talk as it did clarify my general knowledge on radiation and the volunteers are also able to answer questions.

After the presentation, we got a chance to use some of the radiation detection equipment on samples that the audience had brought.It was revealed that some household things such as the inside of a common smoke detector sends the Geiger counters into a frenzy, but only at a 1cm distance. The purpose of these demonstrations was to show that while something may read high, it is not a threat to our health because beyond 1cm the radiation is undetectable and cannot penetrate human skin, just don’t lick it. The proper use of the machines is critical for any sort of accurate analysis. I had brought a bit of soil from my balcony that has been absorbing lots of rain water and also one of the leftover hassakus that I had collected in my neighbourhood. The results of the test we did cannot be considered extremely accurate, as we didn’t do proper control testing and we didn’t take counts for longer 5 minutes, but the basic conclusion was that the soil was fine, but the peel of the hassaku had an insignificant, though measurable, about of beta radiation (an amount that would occur naturally) and an amount of alpha radiation that may be of slight concern. So, I became slightly concerned, but the Safecast volunteers, who have been finding very alarming levels of radiation in produce in Fukushima, were totally unconcerned and proceeded to eat the fruit. I really don’t have the authority to get very technical here, but it seems that things growing in Tokyo are generally fine.

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