by Robert Jacobs, March 9, 2016
originally published here
When we look at maps of Fukushima what we see is disinformation. The maps of the radioactive contamination of Fukushima contain contradictions that embody our inability to understand the true nature of the dangers to people living there. This is rooted in the difficulty in understanding radiation. If we can separate the maps, we may be able to grasp the dangers more readily, and thus understand the situation in a more functional way.
Similarly, one can hold a Geiger counter up in the air in a village in Fukushima prefecture and declare that there is no radiation present. The assumption, therefore, is that there is no danger. The ways in which this can be both true, but only partial truth, are part of what we need to fully grasp to understand the situation in Fukushima.
I will begin with the Geiger counter.
Radiation is a very difficult thing to understand. For starters, we tend to assume that radiation is a “thing.” Something is radioactive or it is not. We are affected by the radiation or we are not. This is not quite accurate. Radiation is a quality: it is a process—something radiates. How it radiates can differ, and it is in this difference that half-truths can be told as whole truths. While there are many aspects to this, for the present article I will concentrate on the differences between gamma, beta and alpha radiation. Most of the discourse that you hear about radiation related to Fukushima is describing gamma radiation. The danger to most of the people continuing to live in contaminated areas is in the form of alpha or beta radiation, so when we hear people talk about radiation in Fukushima, most of the time they are not talking about what is of most concern and danger.
Here is a quick primer. Gamma radiation comes off of radioactive materials in waves. These waves can penetrate anything, and they are partially filtered by heavy materials, such as lead. You can think of gamma radiation as similar to x-rays. This is why you have a lead apron placed on you when you have dental x-rays, and why the technician goes behind a lead-lined wall. When gamma radiation passes through your body it does not stay in your body. Like x-rays, when the source is turned off, they stop and there is no more danger. To limit the damage to the body from gamma radiation we limit the total cumulative dose received, hence the person working with it protects themselves behind the lead wall; the patient receives a small dose, but if the technicians received that same small dose repeatedly every day, they would be at much higher risk.
Alpha and beta radiation comes from specific irradiated particles, such as individual atoms of plutonium, or cesium-137. These particles cannot penetrate through materials: they cannot penetrate through skin, or even paper. They are primarily dangerous when we internalize them inside of our bodies and they permanently lodge there. They generally give off a small amount of radiation because they are single atoms. If there are a lot of them present, they give off more radiation. If one is internalized into the body, it will give this small amount of radiation to the same surrounding cells for 24 hours a day. While the amount is small, 24/7 exposure to this radiation may cause mutations to these cells, and then cancer.
Gamma radiation fills an area equally, lessening quickly as you get further from the source. This is what most Geiger counters are set to measure—the levels of gamma radiation present. When you have alpha and beta-emitting particles scattered in an area, the amount of detectable radiation will likely vary. In Fukushima City last year (about 50 miles away from the nuclear plants), I held a Geiger counter at chest level on a street and found a low level of radiation. However, moments later when I placed that same Geiger counter on the ground, I found much higher levels of radiation. That is because particles fall and collect on the ground. When I then moved my Geiger counter to the gutter at the side of the street, I found dramatically more radiation. This is because rain washes the particles to the gutter. So the distribution of the particles is irregular, depending on how long ago they fell-out of the sky (fallout) and how much wind and rain there has been.
This is how you can hold a Geiger counter in the air (or place a public Geiger counter five or twenty feet in the air) and show very low levels of radiation, and yet there can still be significant dangers present. If the danger is from alpha and beta-emitting particles, the readings taken in mid-air can be low. The way that such particles are dangerous to us is if we internalize them into our bodies, typically by inhaling them, swallowing them, of having them enter through cuts in our skin. Once inside the body, they may pass through, but they may also permanently lodge there. The body is tricked into thinking that these particles are useful chemicals. Strontium-90 “mimics” calcium, and the body can put it into the bones. Since the body puts iodine into the thyroid gland, if someone has internalized iodine-131 (a radioactive form of iodine) the body may put that in the thyroid gland. Thyroid cancer is one of the first cancers to develop from internalized particles, and that is why our conversation about the health impacts in Fukushima are currently focused on thyroid cancer. Other cancers will follow as we move through their latency periods.
Some isotopes of concern after a nuclear accident:
Plutonium 239, half-life: 24,000 years, decay mode: alpha, decay energy: 5.24 MeV
Strontium 90, half-life: 29 years, decay mode: beta, decay energy: 0.546 MeV
Cesium 134, half-life: 2 years, decay mode: beta, gamma, decay energy: 0.698 MeV
Cesium 137, half-life: 34 years, decay mode: beta, gamma, decay energy: 1.76 MeV
Iodine 131, half-life: 8 days, decay mode: beta, gamma, decay energy: 971 keV
Tritium, half-life: 12 years, decay mode: beta, decay energy: 18.6 keV
Decay energy is measured in electron volts (eV), a measure of the particle’s momentum. 1 MeV is 1,000,000 eV, and 1 keV is 1,000 eV. According to the table, Plutonium 239 is the most dangerous internal emitter, but the hazards to public health depend on the relative quantities released and the relative quantities that people actually absorb. Some segments of the population are more vulnerable than others. Is it a matter of a single exposure or a continual exposure and accumulation? What parts of the body do different particles tend to go to, and how long on average do they tend to stay in the body (the biological half-life)? None of this complexity can be conveyed with a map and a simple declaration of a “safe” limit of external gamma radiation exposure. （Table added by Dianuke editor)
These alpha and beta-emitters are particularly dangerous for children. Children are lower to the ground to start with, tend to put things into their mouths, and tend to play outdoors and suffer cuts and bruises, and since their bodies are growing rapidly, damage to cells can replicate faster. This is why parents agonize over whether to stay or evacuate an area that has had radiological fallout.
This is also why it is hard to be certain about the contamination to the food supply. It is virtually impossible to test all food, and so samples are tested: samples of rice from rice fields, samples of fish from catches, samples of fruit from orchards. Because the danger to these crops is not from gamma radiation, which would be equally distributed, but from their internalizing alpha and beta-emitting particles, portions of a crop, or haul of fish, can test negative while other portions contain significant amounts of radiation deposited on them or taken up through soil and water into the plant or fish itself.
Our ability to technologically determine the distribution of alpha and beta-emitting particles is limited because of the irregular deposit of the material from fallout clouds, and the subsequent scattering of the particles from wind and water. This is also why it is possible to “decontaminate” an area only to have it re-contaminated as the wind and rain redistribute the particles that fell on nearby forests. Technically it is not possible to “decontaminate” a natural area. The radioactive particles will remain dangerous for their natural life. For plutonium that is over 100,000 years. During that time, it cannot be decontaminated, it can only be moved. We can attempt to contain these particles, however most of them will long outlive the plastic bags into which we placed them, at which time they will re-enter the soil and the ecosystem and begin to cycle through it again.
Understanding the difference between the dangers from gamma, beta and alpha radiation is the key to understanding how the maps of Fukushima are broken. Below is a typical map that we see of Fukushima, produced by the Japanese government:
There are two things that I want to point out. First, the concentric circles. These have the Fukushima Daiichi nuclear plant at their center. The second thing is the color coded splotches and streak. These show where the plumes of the three nuclear plant explosions deposited their fallout, in this case specifically measurements of cesium-134 and cesium-137. Notice how the representation of the areas of fallout are constrained by the outermost concentric circle.
These two things should be read separately.
Concentric circles describe relative distances from a point. In this case, distances from the nuclear plant. People were evacuated based on their distance from the plant. The mandatory evacuation zone was at 20 km and the suggested, or prepared evacuation zone was from 20-30 km (the key difference between “mandatory” and “suggested” evacuation is liability). The reason that people had to evacuate from these areas was because of the high levels of gamma radiation coming from the melted cores of the nuclear plants, and the high levels of gamma radiation where the plumes deposited the largest amounts of fallout close-by. The levels of gamma radiation near the reactors is lethally high. At this point, no human being can enter into the buildings where the nuclear cores melted. The gamma radiation levels are so high that they would be killed in minutes. We have yet to build robots capable of operating in these highly radioactive locations for longer than an hour or so. Moving away from the point at the center of these circles will decrease one’s exposure to radiation. The amount of gamma radiation coming from the plant is measurable and relatively constant across the areas at similar distances. Hence the use of circles, concentric circles marking decreasing levels of gamma radiation.
Here is a map of the evacuations:
When we look, instead, at a map of the radiological contamination of the downwind area, we are reading entirely different information. The splotches of color marking the levels of radiation from the plumes is irregular, unlike the neat and cleanly measured concentric circles. The colors mark the different grades of radiation from the fallout. They are created based on the gamma radiation from the fallout, however, the primary danger to people living in these areas is not based on the levels of the gamma radiation, but from internalizing individual alpha and beta-emitting particles. Since there is no single source, like the melted cores, but rather billions of individual particles, once the plume has fallen out and the particles have reached the ground, they begin to move through the ecosystem via the dynamic motion of wind and water, and then they are internalized in the bodies of animals. Rain will collect them along gutters and gullies and transport them. Wind will blow them along hillsides and valleys. Once these particles begin to move through the ecosystem, there is no center, no specific source that people must move away from. The dangers are unevenly distributed, and they are constantly changing. Once you are over 30 km away from the nuclear plants, surrounded by their concentric circles, moving further away from the direction of the plants may or may not provide more safety. The contamination that comes from alpha and beta-emitting particles is unpredictable, irregular, and changes over time. Each specific particle has a specific period of radioactivity and during that period, it will move through the ecosystem, being taken up by plants, moved by wind, entering soil, eaten by animals and returning to the soil when the animals die. They may move in the same direction that you are moving to get away from the center of the concentric circles, if the wind is blowing that way.
Here is a map showing the radiological contamination of the region, which differs from the specific places where the plumes first deposited:
The maps of Fukushima are broken. These broken maps are reflections of the broken chain of information that has been provided to those living there and grappling with the dangers on a daily basis. Because these maps, and this information, are broken, disinformation can thrive and blossom. A March 7th editorial in the Yomiuri Shimbun in Japan makes use of these broken maps and the data that they convey to misinform people in Japan about the safety of former residents moving back into contaminated areas. With no sense of irony, it’s headline proclaims, “Correct Understanding of Radiation Needed to Speed Reconstruction.” Explaining that exposure to radiation is natural, the editorial claims that, “The government needs to continue carefully explaining to residents that there will be no health problems as long as the radiation exposure is at 20 millisieverts or lower.” For this reason, people need “correct understanding” to cooperate and return to areas that can only be decontaminated to 20 millisieverts. While there is significant debate about what level of gamma radiation is safe, and increasingly convincing data that no level is safe (see here), this argument ignores the fact that much of that 20 millisievert exposure is coming from alpha and beta-emitting particles, which pose an additional danger from that of the external exposure. For the people being advised to return, the areas they would return to are plagued by the more urgent risk of internalizing these particles, a danger that increases dramatically in areas where the external exposure is still measurably high. Their lives would be filled with the presence of large amounts of invisible atoms that will very likely cause cancers if inhaled or swallowed. These dangers are not factored into the 20 millisieverts the editorial writers so casually dismiss.
These broken maps, co-mingling the dangers of external and internal radiation in one graphic, present the idea that the dangers from radiation near Fukushima are fixed and knowable. This is not true. Massive amounts of radionuclides have deposited along large areas of Fukushima, and they will now pulse and fluctuate within the dynamics of that ecosystem for as long as each particle remains radioactive. Most of them will be hard to trace and difficult to control. People can be moved away from the plants, where the danger is in a fixed location and is measurable. Where the plumes deposited the particles the opposite is true. The dangers are unknowable and can move around, just like the people. This puts the health of those living there in a very different relationship to the risks.
To fix the maps, we need to fix the knowledge chain. Radiation is difficult to understand, and that difficulty allows disinformation to take root–disinformation like that contained in the editorial of the Yomiuri cited above, and in so many pronouncements from experts who omit information about alpha and beta-emitting particles and the dangers of internalized radiation when they speak down to people who must live with these dangers. For most people having to live with the radiation scattered by TEPCO’s meltdowns, clear information about internalized radiation and how these dangers persist in their communities is essential for them to map their own paths to a future of their choosing. No one should insist that they live with higher levels of radiation by changing their understanding to the “correct understanding.”
Robert Jacobs is a historian of nuclear technologies and radiation technopolitics at the Hiroshima Peace Institute of Hiroshima City University.