NOTE: I am updating this post to reflect some of the comments, further research, and input by experts.
Japan’s science ministry says 8 per cent of the country’s surface area has been contaminated by radiation from the crippled Fukushima nuclear plant.
It says more than 30,000 square kilometres of the country has been blanketed by radioactive cesium.
The science ministry defines places with a concentration of more than 10,000 becquerels per square meter as “areas affected by the nuclear accident”…. The science ministry fine-tuned its methods by subtracting levels of naturally existing background radiation.
Fukushima, like most international stories, has a very short half life in the U.S. media — a lot shorter than that of radioactive cesium. As the NY Times noted back in March, “Over the long term, the big threat to human health is cesium-137, which has a half-life of 30 years.”
So the two stories that make today’s mash up headline come from ABC — the Australian Broadcasting Company, that is. The lead story is “Radiation covers 8pc of Japan”:
The ministry says most of the contamination was caused by four large plumes of radiation spewed out by the Fukushima nuclear plant in the first two weeks after meltdowns.
The government says some of the radioactive material fell with rain and snow, leaving the affected areas with accumulations of more than 10,000 becquerels of caesium per square metre.
As you can see from the map above (posted here), a large fraction of the affected area received 60,000 to 600,000 becquerels per square meter, which is a range that, I think, should cause concern. If you are in that zone, it is probably prudent to take steps to determine if you live, work or send your kids to school in places at the high end of that range — and, if so, take steps to avoid prolonged outdoor exposure.
As you can see on page 24 of “Fukushima Accident: Radioactive Releases and Potential Dose Consequences,” 300,000 becquerels per square metre is 5 milliSieverts in the first year and the 10 year dose is 19 mSv — considerably higher than 1 mSv per year. The International Atomic Energy Agency clearly states, in its “Radiation Safety” booklet:
The dose limits for practices are intended to ensure that no individual is committed to unacceptable risk due to radiation exposure. For the public the limit is 1 mSv in a year, or in special circumstances up to 5 mSv in a single year provided that the average does over five consecutive years does not exceed 1 mSv per year.
It is true that people do not spend all of their time outdoors and the additional cancer rates at these levels are quite small.
But based on my conversations with experts, including NRDC’s Tom Cochran, anybody who lives in that area of 60,000 to 600,000 becquerels per square metre has a legitimate cause for concern — since they don’t really have any way of knowing whether they are in the low range zone or the high range zone. They should certainly take steps to acquire more information about the radiation exposure for themselves and their family, and then make decisions on their own about the risk they are willing to take. I will do a post on this later in the week.
The NYT noted the danger of cesium:
Cesium-137 mixes easily with water and is chemically similar to potassium. It thus mimics how potassium gets metabolized in the body and can enter through many foods, including milk. After entering, cesium gets widely distributed, its concentrations said to be higher in muscle tissues and lower in bones.
Climate Progress previously reported on one of the impacts of all that radiation (see Fukushima Surprise: Radioactive Rice “Far Exceeding” Safe Levels Found in Japan).
It must be pointed out that according to the best scientific evidence, it is prudent to avoid even low levels of radiation:
A preponderance of scientific evidence shows that even low doses of ionizing radiation, such as gamma rays and X-rays, are likely to pose some risk of adverse health effects, says a new report from the National Academies’ National Research Council.
Now, ABC reports, “Fukushima crisis ‘stunting children’s growth’ ” — but the cause may surprise you:
“Thousands of children living in the fallout zone are confined indoors because of radiation fears” (Photo: Reuters)