The Ocean of Light above the Ocean of Darkness
“…there was an ocean of darkness and death; but an infinite ocean of light and love, which flowed over the ocean of darkness.” (George Fox, An Autobiography)
Grief was our first reaction when a civilized nation so prepared for earthquakes was devastated. Those of us who live in earthquake country found it hard to tamp down the fear that we can’t protect ourselves from nature. Japan, so much better prepared than the West Coast, actually did quite well with the once-in-a-millennium earthquake (the previous largest in that area was M8.3, in 869 CE), but the tsunami killed thousands, left hundreds of thousands homeless, and may have a cost of hundreds of billions of dollars.
The city of Sendai after the earthquake. Cleanup from the tsunami is expected to take years, and this will delay rebuilding. Less than one fifth of tsunami rubble had been removed by the beginning of June.
Added to our grief, fear was triggered. Something was happening with the nuclear reactors, especially at the Fukushima Daiichi plant. The reactors appeared to have survived the earthquake, but they were not prepared for a 15-meter tsunami. It was hard for anyone, expert or not, to follow the news, with six reactors to track and unfamiliar terms (what did “partial fuel meltdown” mean?), while relying on insufficient and contradictory information from the Japanese (some of it was mistranslation and preoccupation with other matters, some was lack of information, but initially some was an inadequate understanding of the importance of keeping everyone informed).
In general, Western media coverage of Fukushima ignored the arguably greater stories of the effects of the earthquake and tsunami, and how well prepared other countries are for natural disasters; context was uneven at best. According to BBC criticism, journalists were provided with experts on a variety of topics, but far too many rejected the explanations of experts in nuclear power, whom they saw as biased. As a result, their coverage tended to be both alarmist and error-ridden. Media reports continue to change and are sometimes contradictory, and for many of us, the lack of consistent information, along with a very reasonable perception that the event was out of control, fed into worst-case scenarios.
Worst-case scenarios reflect a natural desire to figure out what might happen next, and they can be useful guides to what we need to prepare for, but only if they bear some relation to reality and probability. Poor policy decisions can follow if we fail to differentiate between internal fears and external reality.
|Damage at Fukushima Daiichi|
Currently (as of late May), the situation is not yet stable; three Japanese nuclear reactors in use at this time will likely leak radioactivity for weeks. (The total leakage of cesium and iodine is so far equivalent to 10 percent of Chernobyl, and this may rise a bit.) Three others are in cold shutdown and remain unlikely to constitute a danger. There are still concerns about four of the six spent fuel pools. In particular, risks remain in the form of the threat of aftershocks to stressed containment structures filled with water. The radiation outside the plant boundaries is fairly low, except in a couple of sites, and radioactivity levels continue to fall everywhere outside the plant. Tokyo Electric Power Company hopes to reinforce buildings, clean away the rubble, install proper cooling systems to bring temperatures down below boiling, and deal with the contaminated water. This will take months; full decommissioning will take years.
What often gets lost in the coverage of these developments is that, from what we know now, all the reactors appear to have survived the once-in-a-millennium earthquake (future analysis will show whether this is true), but three, shutting down as planned in response to intense acceleration, did not survive the accompanying tsunamis. This is in part because of design decisions (placement of diesel generators, and inadequate redundancy —extra generators in case some failed, and extra solutions if the generators failed) and design flaws in the current Generation II reactors that have been fixed in the new Gen III+. (U.S. construction of Gen III+ will begin in a few months at the Vogtle plant.) Older reactors rely too much on pumps and valves, while new reactors depend more on gravity and hot material expanding.
Although the threat to human health is smaller than what is widely believed, there may be a public health effect from the damage to the Japanese reactors. As of late May, the 21 most exposed workers have each seen an increase of 0.4–1 percent in their chance of contracting a fatal cancer (Update: Tepco has now examined all 3,700 workers; 107 workers have from 0.4 – 0.8% chance of a fatal cancer, and another 17 have higher exposures, with chances of fatal cancer as high as 5%.) Exposure levels for other workers and the public are much lower, but one can assume that the sheer volume of exposure will produce statistical cancers, cancers predicted by the model, but occurring at a much lower rate than year-to-year variations, with vanishingly small chances of any one cancer being caused by this event. On the other hand, if the nuclear reactors were replaced with coal, in much less than a year, deaths from coal power would clearly exceed total health threats from the Daiichi disaster.
The clean-up cost will surely be in the billions, and the cost to the energy infrastructure will be enormous: Japan will have insufficient electricity for industry for years, because of the damage to the grid and to sources of electricity (both nuclear and not), and will pay higher costs for rapidly acquired sources, like coal and natural gas. The cleanup will take months, and its cost will add to the wider effects of the earthquakes and tsunamis: high death tolls (today 23,000 are dead or still missing), years of cleaning up tsunami debris, tens of thousands homeless, and damages in the hundreds of billions of dollars. The cost of the meltdown will also include compensating residents in the evacuation zone for the disruption of their lives.
Although the public health effect from the damaged reactors appears small, and although, as the Washington Post says, “Barring a major release of toxic elements from the stabilizing Daiichi plant, radiation experts predict no long-term health impact on residents in the region,” the fear of health consequences remains large. People tell me they expect deaths within a year and then a large number of deaths over decades, simply because of the extent of media coverage. Likewise, alarmist actions, such as the Swiss government moving its embassy out of Tokyo, caused some evacuees to assume there was a risk to their health, which made returning home stressful. The greatest health consequence of Daiichi, by far, will be on all whose lives are affected by future energy policy decisions influenced by public overreaction, such as Germany’s decision to replace nuclear power with fossil fuels.
Such misplaced fear continues to be fed by the powerful reaction to Chernobyl. Some popular estimates, such as those by Greenpeace, magnify the tragedy many fold. Chernobyl has actually killed 50–60 to date, and may kill 4,000 more over seven decades following that initial exposure. Four thousand is the number who die worldwide from air pollution every year by noon on January 1, according to World Health Organization. WHO says that at least this number died from climate change worldwide over a typical ten-day period in 2000. There would have to be several Chernobyls every month to yield the damage routinely done by fossil fuels.
Of course, fears about all things nuclear are not without foundation. Nuclear weapons produce a much larger explosion per weight than conventional bombs, allowing the United States to carry a single, enormously destructive bomb in an airplane, and drop it —twice —with horrifying consequences. The world learned nothing new from Chernobyl; the Soviets learned in 1986 what everyone else knew from day one: that you don’t build power plants using an extraordinarily bad design and then hire a director who is not trained in nuclear power, didn`t follow procedure, and didn’t notify anyone or order evacuations. Radioactivity can kill, but it can also save people’s lives, such as in cancer treatments, though even medically it is dangerous and can be misused: radiation treatment for acne is a bad idea, and we’ve learned to protect X-ray patients and technicians with lead aprons.
For many, however, sensible fear of radioactivity has become over-generalized, spilling over, for instance, to the essentially negligible radiation (not radioactivity) from cell phones. If we generalized our fear of radioactivity any further, we couldn’t fly, or visit cities with naturally high background rates of radioactivity, and we’d definitely have to do something about that radon in our basement. We would avoid a number of foods, stay out of brick buildings, and avoid extended contact with other people. There is radioactivity all around us, the largest non-medical source being radon, which EPA estimates kills 21,000 people in the United States each year, yet only suggests mildly that we check our houses and get something done.
Since we couldn’t live with such a generalized fear of radioactivity, we focus on the sources of greatest threat, as we see them. Without checking for or understanding relative levels of exposure, we may fall for alarmist claims and for remedies for dangers that do not exist. For example, there were a number of reports of people outside Japan entering poison control centers for treatment for unhealthy doses of potassium iodide, use of which was not called for in the circumstances. Like everything else in the air, including coal pollution, radioactive isotopes from Fukushima did indeed spread to other countries, but outside Japan, exposure from Daiichi nowhere exceeded radioactivity levels from the ordinary activities listed above.
Such a state of fear can trap us, shaping our responses and blinding us to actual problems we might otherwise address. It is especially hard to put things in perspective when we limit ourselves to like-minded acquaintances who invite us to see the world in terms of us versus them. A surprising number of people seem never to tire of confirmation that we are good, they are bad. Others act and believe differently because they are rapacious and callous, while we act out of intelligence and loving kindness.
Fear of other can obscure and distort our perceptions of actual risks. For better or worse, one doesn’t have to seek sources of risk in one’s own behavior when there is a convenient other to blame for untoward outcomes, such as callous scientists and industry, inadequately regulated by government. When we see a government such as that of Japan, a technologically advanced country, dealing with a crisis in which everything seems out of control, we lose faith in our own government’s ability to prepare for and deal with unpredictable events like nuclear meltdowns. Oddly, we find we prefer far greater dangers that we have come to expect (like the numbers of deaths from coal and hydro power) to the sense that something may happen that we can’t see coming. So, after 33 years of safe use of nuclear power in the West after Three Mile Island, the riveting image that dominates our nightmares remains Chernobyl, multiplied many times over in our press though it bears no relation to what happened in Japan —in cause, handling, severity, risk, and outcome. (TMI is another pivotal image for many, and events in Japan are, in fact, scarier than TMI, a reactor with core meltdown but far fewer complications.)
Nuclear power plays a pivotal role in the we-good, they-bad fights among many Friends.
While we steep ourselves in fears of what might happen at a nuclear plant this month or next, the climate continues to change at a frightening rate. International Energy Agency says that infrastructure now in place and under construction has almost locked us into atmospheric greenhouse gas levels exceeding 450 parts per million. The newest climate model includes feedback, and concludes that temperature increase at 450 ppm, if it were achievable, will be a higher-than-expected 2.3íC. Unfortunately, it is more realistic to expect temperature increases of 3–4íC, with even our best efforts unable to avert serious consequences. For example, a 4íC (7íF) increase in temperature could make the hottest day of the year 18–22íF warmer in eastern North America, and have equally dramatic effects on water supplies; the UK’s Met Office warns that this could occur as early as 2060. In northern California, it’s expected that the San Francisco Bay level will rise 16 inches by mid-century and 55 inches by the end of the century; this assumption is not worst-case.
An unquestioned allegiance to any particular solution to climate change, without critically checking our understanding, throws us back into we-good, they-bad gamesmanship. No one can assure us that the next set of mistakes at a nuclear reactor, with or without a precipitating act of nature, will not end in death. Insisting that the nuclear industry be perfect allows us to ignore all the ways we are failing to address climate change, indeed colluding —out of ignorance, illusion, or indifference —with the many forces that threaten life as we know it.
Having a world that simplifies to black and white —feeling sure we are right, thinking we know who’s wrong —appeals to all of us. When our minds are rooted in fear, and when so many share our fears, it is easy to believe those fears are well-founded. The consequences of this assumption for ourselves and the Earth can be serious.
All forms of energy have risk. To compare relative risks of various energy sources, we use the unit: deaths/Terawatt hours (TWh =1 billion kWh). For perspective, world electricity production was 20,200 TWh in 2008 (8,300 TWh coal, 4,300 TWh natural gas, 1,100 TWh oil, 2,700 TWh nuclear, and 3,300 TWh hydro). The U.S. produced 4,300 TWh in 2007 (2,100 TWh coal, 910 TWh natural gas, 60 TWh oil, 840 TWh nuclear, and 280 TWh hydro).
Over the past 50 years, nuclear power has suffered three significant accidents. In this case it is instructive to compare the number of deaths so far attributable to nuclear power (in the past, present and future), from events occurring in the past 50 years. To calculate deaths/TWh for nuclear power worldwide, divide 4,000 deaths from Chernobyl by 63,000 TWh since 1970. Fukushima will not substantially change that number —the estimate of deaths from Fukushima over seven decades, not yet released, will surely be small, most likely less than the number of deaths caused by a day or two of U.S. coal use. No one has died from U.S. nuclear power in the same time frame. This computes as 0.06 deaths/TWh in the world, including 0 deaths/TWh in the United States.
Air pollution and miner deaths from coal are estimated at 14,000/year in the U.S., and more than 110,000 worldwide. (An additional 200,000 die from direct coal use such as cooking and heating.) In contrast to nuclear’s 0/TWh, coal power produces more than 6 deaths/TWh in the United States (this will decline with new EPA regulations), and a perhaps conservative estimate of 13 deaths/TWh worldwide, not counting climate change. (As of 2000, deaths from climate change had reached 150,000/year.)
Many have told me that the numbers in the prior paragraphs are irrelevant, that their eyes glaze over. This concerns me. When someone tells me it’s not just the number of deaths, real or potential, that concerns them, I ask them what feels more important. People give various responses, most quite heated: the arrogance of pro-nuclear people, or that radioactivity can travel around the world, or that nuclear power is an industry and so cannot be trusted. Somehow, finding a radioactive isotope from Japan as far away as Boston is worse than air pollution from Asia killing Americans or U.S. air pollution killing people east of us. Somehow, the fact that the radioactivity in groundwater near nuclear waste repositories, which at its peak (e.g., Yucca Mt 300,000 years from now) will offer levels of exposure equivalent to moving from New Mexico to Washington State, is more feared than the pollution of all groundwater, everywhere on Earth, by 20th-century toxic chemical waste, spreading from its source to even the remotest places. Somehow, the long-term aspect of nuclear waste, even though it has a minimal impact, is more important than the permanent changes (until long after our species has gone extinct) we are imposing on the atmosphere and biosphere through fossil fuel use. Somehow it doesn’t matter that expert analysis (Intergovernmental Panel on Climate Change) shows that opposition to nuclear energy means more fossil fuels. (Germany will have to add coal and natural gas if it permanently shutters its nuclear power plants.) Somehow nuclear power is still scarier and the numbers don’t matter.
Some who hate to compare numbers prefer to distance themselves from any pollution source, asserting they support only clean energy sources, like solar, and tending to paint alternatives in elevated terms, as natural, pure, sustainable, and risk-free. Solar, wind, and living with less are all seen as answers to nuclear power’s perceived risks. Some may even convince themselves that solar and wind are cheaper than nuclear. Numerous concerns exist about renewables, including wind causing climate change, according to analysis in recent years (also see David McKay’s Sustainable Energy —without the hot air). A major problem with intermittents, including solar, is that they achieve less than 80% of those expected greenhouse gas reductions, because the backup fossil fuel they require runs inefficiently, just as cars in city driving get fewer miles to a gallon. NOx reductions are even lower. And while solar manufacture is no worse than other industries, and solar energy is considerably cleaner than coal and other fossil fuels, it is not pure. (Brookhaven provides a more complete list of toxins associated with solar power manufacture.) In short, the numbers are essential to compare the actual impact of different sources on human health and the environment.
Real people are dying from air and water pollution. They tend to be the very young, the very old, and those with other health problems. They are frequently people who have other disadvantages in life. The 150,000 who died from climate change in 2000 (from disease, floods, landslides, and starvation) are also real people. I’ve never heard anyone get as angry about those 150,000 (presumably more this year, and the numbers are expected to increase rapidly beginning this decade) as some Friends get about the thought of even one death from nuclear energy. Perhaps the problem is not that the explanation includes numbers that are numbing to some readers. The problem might be that today, the effects of climate change are small among people we know and care about (which will not be true in 20 years). Perhaps air pollution is just part of the air we breathe.
Everyone knows how difficult it is to process the overwhelming amount of information bombarding us when we try to understand a complex and long-term challenge like climate change. It is even harder to figure out how to respond. We can look with some compassion on our sense of helplessness, our tendency to take refuge in distractions, or look for the little things in life we can control. However, some of us really do need to stay focused on the large issues surrounding climate change and pay attention to the numbers, if society is to stop resisting meaningful solutions and move towards meaningful change.
A fear that says, “Well, nuclear power may end up killing someone” is, in this way of thinking, allowed to take precedence over far greater dangers to human beings. Any fear that says, “My fear is more important than the facts,” a fear based on “what ifs,” blinds us to steps that would address real and present dangers. No one can promise us that we will never be afraid. I carry great fear of both the likely and possible consequences of climate change. Part of me wants to cry, and part of me wants to act out of that fear; only the former sometimes helps. As long as I live in this world, I will move at times into the ocean of darkness created by my fear. I can only hope to find a way back to the ocean of light. We can all work more consciously to rise above our private and shared fears to seek the light of understanding and good works. q
An explanation of units (includes likely health effects)
Stewart Brand says in Is obfuscation deliberate?, “With its babble of measurements, the nuclear power industry has guaranteed that all of its communications with the public are maddeningly confusing and frightening.
“It is such conspicuously incompetent social engineering that observers understandably suspect that the nuclear engineering behind it is equally incompetent, and that nuclear engineers must hate people.” This is an attempt to provide help translating the babble.
A number of units have been used by the media, and per usual, there is more than one set of units. The material in this section draws heavily on David Bodansky’s Nuclear Energy, 2nd Edition, chapters 3, 4, and 15.
The media commonly use two types of units. The first is decay rate: 1 becquerel (Bq) = 1 decay/second, but Geiger counters often use counts per minute (1 cpm = 1/60 Bq). Another unit for decay rate is the curie: 1 Ci = 3.7 x 1010 Bq. Common prefixes are milli (m), micro ( µ), and pico (p), and indicate one thousandth, one millionth, and one trillionth.
The unit for absorbed dose, gray, is often used for cancer treatments, and tells us the amount of energy released per kg of tissue. The damage done by alpha particles is significantly more than the damage from beta particles, so the media use instead dose equivalent, sievert (Sv), damage done by a dose. Dose equivalent in sieverts is obtained by multiplying dose, gray, by a weighting factor between 1 and 20; 1 Gy = 1 to 20 Sv (1 for beta particles and gamma rays, 20 for alpha particles). 1 Sv = 100 rem (older unit)
Dose equivalent is the bottom line unit for understanding health risk.
For high doses, dose equivalent is ignored. High doses kill within days to months, although the dose at which half die depends on health and treatment. Half of Hiroshima victims receiving a 3 Gy dose died, while 7 of 23 Chernobyl firemen died at doses between 4 and 6 Gy, and 21 of 22 died at doses above 6 Gy. Radiation sickness —clinical symptoms include nausea and depressed white blood cell count —occurs at doses from 1 – 4 Gy.
The bible for biological effects of ionizing radiation for lower doses, below 1 Sv or 1 Gy, is produced every few years by the US National Academy of Sciences, Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII – Phase 2. NAS uses the linear no-threshold (LNT) model (you may have heard some of the controversy about this model). The basic assumption is that a 9 Sv collective dose produces one cancer, and a 17 Sv collective dose (say 100 mSv = 0.1 Sv for 170 individuals) produces one fatal cancer in the group beyond what would normally occur, and the same collective dose always kills one person no matter how small the individual dose and no matter whether the dose occurred over a short period or years. So 1,700 people each exposed to 10 mSv, 17,000 each exposed to 1 mSv, etc —in each case, one person will die from a cancer from this exposure. This number was obtained by studying cancer fatalities among atomic bomb survivors: detailed analyses of the 7,827 cancer fatalities from 1950 to 1990 deemed 421 “excess”, attributed to extra exposure from the bombs. Because workers tend to be healthier than the general population and are neither young nor old, their risk coefficient is less. In practice BEIR divides estimates of purported effects by 1.5 at the low exposures of the workers and public from Fukushima Daiichi, other groups divide estimates for low exposures by 2, still others ignore exposures below some level. I will use the BEIR tables: here for single dose vs age including children and here for exposures over time.
For those suffering from acute radiation syndrome, the isotope is irrelevant, and only total dose matters. In considering chronic health effects, iodine is more effective at causing cancer, particularly in children —iodine targets the tiny thyroid gland (less than 1 ounce, about 10 – 15 grams), so the dose equivalent (effective dose per kilogram of tissue) from a small amount of radioactivity can be enormous. Radiation damage to thyroids was exacerbated in areas where soil was iodine deficient. So iodine, 90% of the radioactivity released from Chernobyl (not counting xenon, which doesn’t interact with our bodies), caused thousands of thyroid cancers from an exposure that occurred in the few weeks before it decayed away. Since thyroid cancer is very easy to treat, it rarely results in death, however unhappy and scared its victims might be. Juvenile thyroid cancer is a fast acting cancer, along with leukemia.
Tepco examined 3,700 workers for radiation exposure and found 124 received dose equivalents in excess of 100 mSv. Of these, 107 exposures were between 100 and 200 mSv, so BEIR estimates each has less than 0.4 – 0.8% chance of dying from cancer from their exposure. Another 8 had exposures up to 250 mSv (up to 1% chance of a fatal cancer from the exposure), and another 9 had exposures above 250 mSv. BEIR estimates that for higher single doses, men aged 30 have a 5% chance of dying from each 1 Sv, 1000 mSv, dose equivalent, and this declines with age. Cumulative exposures leads to a prediction that up to one of the most exposed workers will die of cancer from that exposure.
The larger Japanese population received a higher collective dose —each person received much smaller doses, but enough were exposed so that statistical cancers are predicted —if you get cancer, the chances are overwhelming that you did not get cancer from this incident, yet the model predicts that several people will get cancer. This contrasts with Chernobyl, where several thousand cancers were clearly caused by that accident (cancers requiring a short time to develop, primarily juvenile thyroid cancer), along with 15 cancer deaths as of 2002. The 2,000 deaths expected among Chernobyl workers, and almost 2,000 deaths expected in the general population over the next few decades are statistical —if you die, chances are extremely good that it wasn’t the radioactivity that killed you, but the model predicts some will die earlier.
Figure 1 This map was created by the U.S. Department of Energy; divide by 100 to get to mSv. The sections in red show areas where people exposed to 20 mSv have 0.08% chance of contracting a fatal cancer sometime in their life from that one year of exposure. The yellow area, with the same assumptions, puts people at half the risk, 0.04%, and the blue area, with the same assumptions, puts people at one tenth the risk, 0.008%. Presumably evacuation plans were made after an assessment of actual exposure, since most people appear to have stayed indoors as directed, at least initially. UNSCEAR ignores cumulative exposures of <10 mSv.
Figure 2 From Japan Atomic Industrial Forum (pdf) Clearly radioactivity is decreasing in the areas around the nuclear plant. Half of iodine-131, the great majority of radioactivity deposited, decays every 8 days. After 40 days (iodine levels down 97%), most of the remaining radioactivity comes from approximately equal amounts of cesium-134, which decays at the rate of 30%/year (half life 2 years), and cesium-137, which decays at 2%/year (half life 30 years).
Table 1 shows some sources of radioactivity in our daily life from a number of activities, as well as background exposure from cosmic rays, the soil, even internal radioactivity. Daily background dose equivalent is typically around 7 µSv.
|Radiation sources||US (NCRP)
|Radionuclides in body (e.g. K-40)||0.39||0.29|
|Cosmogenic (eg, C-14)||0.01||0.01|
|Total for natural sources||3.0||2.4|
|Nuclear weapons testing||<0.01||0.005|
|Nuclear fuel cycle||0.000 5||0.000 2|
|Total||6.2||2.4 + medical|
|TMI, greatest exposure offsite (pdf)||<0.01|
Table 1 Average radiation exposures for the U.S. and world: effective dose in mSv/year (from table 3.5 in David Bodansky’s Nuclear Energy, 2nd Edition, except as otherwise noted). U.S. information from National Council of Radiation Protection and Measurements (NCRP). World information from United Nations Scientific Committee on the Effects of Ionizing Radiation (UNSCEAR).
Background radiation varies widely by country, primarily because of different rock and soil composition:
Figure 3 Average yearly background levels vary widely by country in places where people live, from < 2 mSv to almost 8 mSv. In many places where people live, annual dose equivalents can exceed 10 mSv, as in Denver. The highest exposure, up to 260 mSv, is in a resort town, Ramsar, Iran.
Figure 4 U.S. Sources of Exposure, from National Council of Radiation Protection and Measurements Thoron is an isotope of radon. Divide mrem by 100 to get units in mSv.
For people who live at low altitudes, our largest exposure from natural sources comes from radon. Exposures vary across the U.S. Radon is more of a problem indoors, in unvented uranium mines or basements, because it can accumulate. For people at high altitudes, cosmic rays can be a more important source of radioactivity than radon.
Medical diagnosis exposures range from as little as 0.001 mSv dose equivalents (dental X-ray) to 19 mSv (CT scan for lumbar spine). Americans average about 3.1 mSv in medical procedures per year, but for half of Americans, the dose equivalent is ≤0.1 mSv. About 4 million non-elderly Americans receive dose equivalents >20 mSv each year.
There are other sources of small doses:
- Living within 50 miles of a nuclear power plant: 0.09 µSv
- Eating one banana: 0.1 µSv
- Living within 50 miles of a coal power plant: 0.3 µSv
- Using a CRT monitor for 1 year: 1 µSv
- Dental or hand X-ray: 5 µSv
- Flying: 3-5 µSv/hour
- Sleeping next to someone, 8 hours/night for a year: 20 µSv
- Living in stone, brick, or concrete house, one year: 70 µSv
- Working in Grand Central Station for 1 year: 1.2 mSv = 1,200 µSv
- Astronaut/month: 15 mSv
The linear no threshold model and public health
The LNT model says there is no safe level of radioactivity. However, there is no major public health push to protect the public from even very large collective doses outside of nuclear power and nuclear medicine.
Even confirming the LNT model by comparing exposures is problematic. Only 70,000 live in Ramsar, so any increase in cancer due their exposures, higher for some than the most exposed worker at the Daiichi plant, is unlikely to be seen. Denver has a high level of cosmic radiation, and higher natural background than most of the United States, and lower cancer rates. However, radioactivity is a small contributor to the cancer rate and other factors may influence more where cancer rates are high or low. The linear no threshold relationship was obtained for high doses in a short time, and corroboration for lower doses or longer time periods is more challenging. A number of cancer specialists, physicists, and others disagree that the relationship holds at low doses or over longer periods of time. The evidence is considered “clear cut” for dose equivalents above 200 mSv with weaker evidence down to 50 mSv.
Most use the IAEA calculation of about 4,000 deaths from Chernobyl over seven decades*, but if even tiny doses well below 1 mSv are included, far below variations between different parts of the U.S., then the model predicts 30,000 deaths over 70 years. If the model is correct, it presents major public policy challenges, because the LNT model predicts 30 million deaths worldwide from radon over the same period, as the collective exposure to indoor radon is about 1,000 times the collective dose from Chernobyl (Bodansky pp 112-3). EPA assumes 21,000 Americans die of lung cancer each year from indoor radon, 1.5 million deaths over 7 decades.
There are other inconsistencies: EPA regulations limit radioactivity release from nuclear power plants, and ignore coal power releases that are 100 times larger/kWh. The logic is that it is not cost effective to regulate coal power plants, but why then are nuclear plants required to meet a far more rigorous standard? Safety levels for water and produce vary by country, so tap water in Tokyo at two times Japanese regulatory standards was one-fifth of the European standard. Two pounds of banned Japanese spinach/day for a year would expose the consumer to about the same radioactivity as one fifth of a CT scan, and spinach was banned when it already appeared as if all large releases were over. Health Physics Society, for one, is on record (pdf) disagreeing with the LNT model, pointing to, “(1) 100 to 1000 fold discrepancies in permissible exposure levels among various regulations, all allegedly based on the same scientific risk assessment data, and (2) proposed expenditures of billions of federal and private dollars to clean up radioactively contaminated federal and commercial sites without careful consideration of the actual public health benefits to be achieved.”
It appears governments focus public health concerns about radioactivity on a limited number of activities. EPA does not set a uniform standard for radioactivity release from all power plants, and no attempt is made regulate comparable health danger from all types of power sources —it would be interesting to see health effects compared for regulatory standards for radioactivity and air pollution.
Disputes about estimates from Chernobyl: importance of sources
The most frequent response to my earlier articles in Friends Journal was to attack the legitimacy of IAEA as a source on the health effects of Chernobyl, numbers seen as scientific consensus (complaints about IAEA data and analysis would be well covered in Science and other journals), and this attack has been repeatedly frequently by anti-nuclear people in recent weeks. The argument is that independent researchers, such as Greenpeace, have provided purportedly more accurate estimates of one million already dead from Chernobyl. The basic argument includes an assumption of conspiracy including two United Nations agencies, both IAEA and World Health Organization, and thousands of scientists worldwide. Scientists have a different take on why estimates between the scientific and anti-nuclear communities differ so much, in addition to the assumption that there is no result, no matter how improbably high, that Greenpeace (pdf) would reject:
• Scientists find a cause more likely if increased mortality and morbidity correlate with increased exposure.
• Scientists look at and sort among a number of explanations for increased mortality (including anxiety about Chernobyl and generally since the fall of the Soviet Union, and high consumption rates for alcohol and cigarettes).
• Scientists assume that cancers take at least 10 – 15 years to develop, excepting leukemia (can appear within 2 – 5 years) and juvenile thyroid cancer (can appear within 5 years —childhood thyroid cancer in the areas around Chernobyl peaked in 1995, and adolescent thyroid cancer peaked in 2001), while others include cancers from day one. (IAEA, pdf)
• Scientists assume that health data in the Ukraine and surrounding areas, pre-Chernobyl, are unreliable.
• Scientists do a literature search, and compare the results for other known exposures. For example, no increase in birth defects was observed at Hiroshima/Nagasaki even with much higher exposures (except for women pregnant at the time of the bombings, and this does not appear to have been passed on to succeeding generations), according to Radiation Effects Research Foundation. Since higher exposure from Chernobyl also does not correlate with increased birth defects, the data and the studies agree.
Health statistics for the Ukraine and Russia may correlate better with high alcohol and cigarette consumption, and less well with high rates of radioactivity-induced cancer. IAEA’s The Chernobyl Report (pdf) sees anxiety as the single largest public health factor.
*The estimate of 4,000 eventual deaths from the Chernobyl accident comes from the IAEA/WHO report: One Decade After Chernobyl: Summing Up the Consequences of the Accident
I find it easier to read in David Bodansky’s Nuclear Energy 2nd Edition table 15.3
Among 200,000 liquidators, 2,000 excess cancer deaths are expected from solid cancers, and 200 from leukemia (this represents a 25% increase in leukemia rate). Average dose equivalent is 100 mSv. Among the more than 100 liquidators who survived acute radiation syndrome, exposure from 1 to more than 6 Sv, the chances of a fatal cancer from the accident are considered to be 5% or more, with higher exposure associated with greater risk. (An increase (pdf) in leukemia has been seen in liquidators with more than 150 mSv exposure).
Among 135,000 evacuees from 30 km zone, 150 solid cancers and 10 leukemia deaths are expected (a 5% increase for leukemia). Average dose over a lifetime: 10 mSv.
Among 270,000 residents in the strict control zone, 1,500 solid cancer and 100 leukemia deaths are expected (a 10% increase for leukemia). Average dose over a lifetime: 50 mSv.
Of the 4,000 fatal cancers expected from Chernobyl, more than half are expected among the 200,000 liquidators (1% chance of dying from cancer as a result of Chernobyl). Among the 400,000 most exposed members of the public, the chances of getting a fatal cancer from Chernobyl are less than 0.5%. Assumptions include a somewhat longer life expectancy than is now seen in Ukraine.
Some reports also consider that among 6.8 M in other areas, 4,600 deaths solid cancer and 370 leukemia deaths are expected. Average dose 7 mSv. UN Scientific Committee on the Effects of Atomic Radiation (pdf) ignores this group.
Outside of thyroid cancer, the LNT model predicts about one death for every two cancers. Except for thyroid cancer and leukemia (liquidators with more than 150 mSv exposure have seen an increase (pdf) in leukemia), cancers typically occur decades after exposure.
Timeline and General Coverage
• World Nuclear Association provides very readable coverage of most major aspects of the events, including a Fukushima Accident Information Paper and a list of reports on their blog. WNA is easier to read than IAEA.
• The US nuclear lobby, Nuclear Energy Institute, provides a Fukushima page, also focuses on events in Japan, and needed responses to the information out of Japan, and describes how the U.S. does it differently.
• U.S. Department of Energy has several slide shows
• Atomic Power Review provides readable day-by-day explanations with details that appeal to the nerd in us all.
• Bloomberg provides a readable description of the first day.
• A number of discussions have begun on mistakes and remedies.
• International Atomic Energy Agency and World Association of Nuclear Operators (created in Moscow after the Chernobyl accident) are two organizations that communicate rapidly and thoroughly what is learned. U.S. NRC will also be influential.
• Updates go on all the time even without accidents. For example, a list of major improvements NRC has ordered since 1979 for the kind of reactors at Fukushima can be seen here.
• the wiki Journalist Wall of Shame
• There are numerous examples of over-the-top coverage. Michio Kaku, a PhD physicist (which does not mean that he is necessarily knowledgeable about nuclear engineering), seemed to be describing a different event.
• Add coverage of problems we know about because of anti-nuclear power folks protest, such as this NY Times article on the Nuclear Regulatory Commission phasing out safety methods (“They weren’t needed for design basis accidents and they didn’t help with severe accidents”.)
©2011 Friends Publishing Corporation. Reprinted with permission. To subscribe: www.friendsjournal.org