Strange Glow
Page 39
It is important to remember that just because an accident has never occurred before, doesn’t mean that it is unlikely to occur in the future. To think that it does amounts to submitting to the black swan fallacy,28 as Professor Lewis explained:
The general argument that the fact that one has operated safely for a finite period of time proves that the safety level is adequate is just not statistically right. … [It is] a psychological trap to believe that because something has not [yet] happened, you are doing just fine.29
PULLING NO PUNCHES
Given that complex systems have high levels of uncertainty that can thwart attempts to precisely quantify the risk of failure, how then should we judge their safety? In such cases, we can sometimes gain insight by just assuming the catastrophe has happened and predicting its health consequences. In other words, if the dreaded event eventually occurs, no matter how great the odds against it, what exactly are the health consequences that we can anticipate? Fortunately, this question is easier to answer than predicting the rate of nuclear core accidents. We can do it by studying similar, worst-case accidents. The value of characterizing the consequences of such a worst-case scenario is that it provides us with two things: (1) we can judge the direness of the worst-case event; and (2) we can determine what type of emergency responses we need to have in place.
In terms of a worst-case scenario for a nuclear power plant accident, Chernobyl offers us an excellent model. The Chernobyl nuclear power plant accident of 1986 was, by far, the worst nuclear reactor accident of all time.30 It resulted from a series of operator misadventures set within an environment of incompetence that was also cloaked in secrecy. The causes of the accident have been studied in detail, and make a good playbook for what not to do at a nuclear power plant, but that’s not our concern here.31 We’re more interested in the public health consequences of the Chernobyl accident.
Although Chernobyl and Fukushima Daiichi both received the highest accident rating (level 7) on the IAEA scale of nuclear accidents, Chernobyl was far worse, affecting far more people. Over 572,000,000 people among 40 different countries received at least some exposure from Chernobyl radioactivity. (Neither the United States nor Japan were among the exposed countries.) It took over 20 years to fully assess the cancer consequences. Finally, in 2006, an international team of scientists completed an analysis of the dose and health data and reported on the cancer deaths that could be attributed to Chernobyl radioactivity.32 Their detailed analysis included countrywide estimates of individual radiation doses in all 40 exposed countries, and region-wide estimates for the most highly contaminated regions (Gomel, Mogilev, Bryansk, Tula, Kiev, Rivno, and Zhytomir) within the most highly contaminated countries (Belarus, Russian Federation, and Ukraine).
Here’s what they found. Even in the most highly contaminated regions, the effective doses the public received from the radioactivity averaged only 6.1 mSv (equal to two years of natural background), and the average dose for all exposed people was just 0.5 mSv (equal to two months of natural background). Using statistical models that accounted for age, gender, and other demographics, the scientists predicted a total of 22,800 radiation-induced cancers (excluding thyroid cancer) among this group of 570,000,000 people. That is, 22,800 cancers in addition to the approximately 194,000,000 cancer cases that would normally be expected in the population even if there had been no Chernobyl accident (i.e., 194,000,000 versus 194,022,800), or a 0.01% increase in the cancer rate.
For people receiving an average dose, we can translate the 0.01% cancer risk (i.e., odds of radiation-induced cancer = 1:10,000) into an NNH of 10,000. Of course, for those in the highest doses group (6.1 mSv), the risk is proportionately larger, but only 2% of the exposed people fell into this higher dose group. That said, on average it would require 10,000 people exposed to Chernobyl radioactivity to expect even one of them to have cancer as a result of their exposure. This number is too small to have any measurable impact on the cancer incidence rates for any cancer registries, so the predicted values will likely remain theoretical. Simply put, the study concluded that there was an immeasurably small number of excess cancer cases that could be attributed to Chernobyl radioactivity in the environment … with the exception of thyroid cancer.
Unfortunately, the one type of cancer that could have easily been prevented was not. Having apparently learned nothing from the Marshall Islanders’ unfortunate experience with iodine-131 (half-life = 8 days), the population surrounding Chernobyl was not warned about the possibility of iodine-131 in milk and other locally produced agricultural products. Had they avoided eating these foods for just three months, nearly all (>99%) of the radiation-induced thyroid cancers could have been prevented. But that did not happen. The people were not warned, iodine-131 contaminated food was eaten, and thyroid cancers resulted. For Chernobyl, even the cancer rates from iodine-131 were a worst-case scenario because much of the local population had an iodine-deficient diet, meaning that their starved thyroids sucked up any iodine that became available, an extreme situation that would not have happened in countries such as the United States or Japan, where diets are richer in iodine. Studies suggest that there will be a total of about 16,000 thyroid cancers produced as a result of Chernobyl iodine-131 exposure.33 Since thyroid cancer is one of the rarer cancers (i.e., it has a low background incidence), excess thyroid cancers due to iodine-131 can more readily be seen as elevated thyroid cancer rates in cancer registries. In fact, a spike in cases was seen within a few years following the accident. Fortunately, thyroid cancers are among the more successfully treated cancers. Of the 16,000 thyroid cancers produced, it is anticipated that at least two-thirds will be cured with standard therapy.34
At Fukushima, there was much less iodine-131 released. Compared to Chernobyl, the thyroid doses from fallout were extremely low, the population exposed was smaller, and people were advised to avoid local dairy products and drinking water due to possible iodine-131 contamination. Iodine-131 uptake into the thyroids of exposed people was later measured and the doses estimated to average just 4.2 and 3.5 mSv, for childern and adults, respectively.35 Compare this to Chernobyl where millions of people received thyroid doses in excess of 200 mSv (i.e., more than 50 times as much)—high enough to see appreciable amounts of excess thyroid cancer. The Fukushima thyroid doses, in contrast, were very close to annual background levels, too low to expect to see a significant increase in clinical thyroid cancer.
At Chernobyl, 127 reactor workers, firemen, and emergency personnel sustained doses sufficient to cause radiation sickness (>1,000 mSv), and some received lethal doses (>5,000 mSv). Over the following 6 months, 54 died from their radiation exposure.36 And it’s been estimated that 22 of the 110,645 cleanup workers may have contracted fatal leukemias over the 20 years following the cleanup.37
As for radiation sickness at Fukushima, there was none, not even among the reactor workers. Two workers who had leaky respirators received effective doses of 590 mSv and 640 mSv.38 These doses are above the Japanese occupational limit for a lifesaving event (250 mSv), but still below the threshold for radiation sickness (>1,000 mSv). Their lifetime cancer risk will increase about 3% (i.e., from the 25% background rate to 28%) due to this exposure, but they are unlikely to have any other health consequences; nor are their future children.
These two radiation workers and others like them are the heroes of Fukushima. They stood their ground and did their jobs despite the risks, and likely saved the lives of others. Radiation workers acknowledge that their profession exposes them to more radiation risk than the general public and voluntarily agree to sustain exposures up to the regulatory limits set for employees, which are routinely 10 times higher than those set for the general public.39 They understand that their profession, like many others, entails some added risk of death, and they accept that risk as a condition of their employment.
Their heroism, however, may come at a very high personal cost, even if their health risks are actually limited to a slightly elevated cancer risk. The
biggest fear for young Kai Watanabe, a radiation worker who fought to save the Fukushima plant, is not the cancer risk but rather that his radiation exposure will cost him a normal life: “Let’s say I tell a woman about my past, that I’ve absorbed all this radiation and may get sick or father children that are deformed, so we shouldn’t have children. Is there a woman out there that will accept me? … Neither of us would be happy with a situation like that. So I think it’s best for me to stay single.”40 It’s a shame that Watanabe would deprive himself of the joys of marriage and fatherhood because of health risks that are actually quite low. This is a tragic example of how exaggerated fears of radiation can damage lives.
With regard to radiation sickness, it is safe to say that the risk from a nuclear core accident is borne almost exclusively by people on the reactor grounds, most notably by the radiation workers servicing the core. It is hard to imagine how anyone off the grounds could get a dose high enough to cause radiation sickness. We have seen, in the case of the Lucky Dragon No. 5 fishermen, that fallout can cause radiation sickness even at great distances from a nuclear detonation, but the fallout levels from a hydrogen bomb are orders of magnitude higher than what can occur from a nuclear reactor accident. And there is no possibility of a nuclear reactor exploding like a hydrogen (fusion) or even an atomic (fission) bomb,41 so the fallout potential is much lower, as we now know from both the Chernobyl and Fukushima experiences.
ASHES TO ASHES
At the time of the Fukushima accident, the radiation threat was out of the minds of earthquake and tsunami survivors. That was a worry for tomorrow. Today had enough problems of its own, and among them was how to account for the missing.
Setsuko Uwabe was hunting for her husband Takuya, but he couldn’t be found at any of the evacuation centers. Setsuko, a cook, worked in the cafeteria of a local nursery school situated on a hillside overlooking Rikuzenataka, a small town up the coast from Fukushima Daiichi. She had spotted the tsunami coming toward shore from the elevated kitchen window of the school, and was able to evacuate herself along with many of the school children to still higher ground just before the tsunami hit. They were all saved. But her husband Takuya, a municipal worker, was working in the town below. She did not see how he could have easily escaped and no one at the evacuation centers had seen him. If not among the living, perhaps he was among the dead. She decided to volunteer at the death registry desk. As long as he didn’t appear on the death registry, she could maintain hope that he was still alive. But beyond gathering information for death certificates, volunteers at the death registry were also expected to help with arranging cremations, a job for which she was not emotionally prepared.
Among the buildings that were destroyed in the Fukushima Prefecture were the crematoria. And even those crematoria that survived didn’t have the capacity to satisfy the heavy demand for cremations. Typically, crematoria are designed to handle less than a dozen bodies per day, while the need was for hundreds of bodies per day. Setsuko scheduled as many cremations as she could, but the fortunate families that were able to secure a cremation time were expected to prepare the body themselves. They were instructed that the corpse needed to be tied to a burnable wooden plank, and wrapped securely with a blanket. Then they would have to find their own transportation to get the body to the crematorium. Also, urns for the ashes were in short supply. They would need to find some type of container among the rubble if they wanted to keep the ashes. For the deceased who had no one to claim them, or had families that couldn’t comply with the cremation requirements, the body was dumped into a mass burial pit.
After a couple of days, Takuya’s body was found near the river, along with the body of his best friend since boyhood. Setsuko went down to the makeshift morgue at the local gym to view Takuya’s remains. He appeared to be sleeping. There was no visible damage to any of his body parts. It was as though life had simply been sucked out of him. With the help of their son and daughter, Setsuko prepared his body as instructed, and transported it to the crematorium. Luckily, they were able to secure a flower vase as a substitute for an urn, and took as much of Takuya’s ashes home with them as would fit in the vase.42
Takuya was just one of many who died. In the end, the death toll from the earthquake and tsunami reached 15,900. In addition, there are 2,600 still missing and presumed dead. No deaths were attributed to radiation exposure, and no significant increases for any type of radiation-induced cancer or inheritable mutations are expected to occur.
THE NEW NORMAL
There were 340,000 people displaced by the 2011 Fukushima disaster. Will it ever be safe for them to go back home? Will things ever return to normal in the Fukushima Prefecture? Good questions.
The radioactivity levels in the Fukushima Prefecture will never drop down to their prior levels within any of the survivors’ lifetimes. The area is too contaminated with radioactive fission products for that to occur. The reality is that, although radioactivity will decay away and dissipate with time, it will always be elevated compared with other areas of Japan. This is an unfortunate fact.
When it will be safe to return is entirely dependent upon how you define safe. As we’ve learned, the term safe really means low risk, and not everyone agrees on what low risk means. The Japanese government has set an annual effective dose limit to the public of 20 mSv as its remediation goal for the Fukushima Prefecture.43 Prior to 2011, one mSv above background was Japan’s regulatory limit for the public. To the Japanese people, this raising of the safety limit appears like the government is backpedaling on its safety tolerance because it knows it can’t deliver on any commitment to reduce the annual effective dose below 20 mSv. This, of course, is true. If they could deliver 5 mSv, then 5 mSv would have been their new safety standard. This is the problem with moving regulatory dose limits after the fact to accommodate inconvenient circumstances. It breeds distrust.
Perhaps the Japanese government would be better off to just explain what the risks are at the various dose levels and let the people decide for themselves if they want to go back. For example, 20 mSv annually is not unlike our earlier situation with an annual whole body spiral CT scan, which also delivers an effective dose of 20 mSv. As you recall, we calculated a lifetime risk of cancer from a whole body spiral CT scan as 0.1% (or odds of 1:1,000). If you lived for five years at that level, it would thus be 0.5% (or 1:200).44 Alternatively, if the effective dose were 10 mSv per year, then the risk would be half of that from 20 mSv. Yes, it’s true that children may be at somewhat higher risk and older people at lower risk, so you may want to take that into account in your personal situation, but overall, these are the typical risk levels. Now ask yourself: Would it be worth it to me to go back to my home knowing I was facing this level of cancer risk?
This is why transparent risk characterization is better than setting opaque safety limits, particularly if you’re going to start moving those limits around to suit the circumstances and, thereby, destroy people’s confidence. The above risk estimates were the same before the accident as they were after the accident. The risk per unit dose doesn’t change with the circumstances, but the “safe dose limit” apparently can. People who think that regulatory limits represent thresholds for safety are quite mistaken. The limits are merely arbitrary lines that are drawn in the sand by some regulatory body, marking the fuzzy border between the dose levels that entail “acceptable” versus “unacceptable” amounts of risk. If you don’t like where that line has been drawn, pick up a stick and draw a different line for yourself. When it comes to risk tolerance, there will always be different lines for different people.
These are the issues people from the Fukushima Prefecture are now facing. It’s not necessary that all of them arrive at the same conclusion about their personal safety. Whether or not to return should be an individual choice, and people can make different decisions, all equally valid, as long as they have the facts they need to make a credible assessment of the situation.
BETWEEN A ROCK AND A WET PLACE
FIGURE 16.1. THE OLDEST TSUNAMI WARNING STONE IN JAPAN. Although the inscription is worn away, the stone in the foreground is believed to be a tsunami warning tablet erected after the great Jogan tsunami of 869 AD. On the day of the March 11, 2011, earthquake, the Miyato-jima Islanders who heeded the warning of this ancient tablet evacuated to higher ground and were saved from the subsequent flood. In gratitude, they installed a new tablet next to the old stone acknowledging their ancestors’ sage advice. The new tablet reads: “Following the tradition of the tablet, thousands of residents could evacuate. We are grateful for the Jogan tablet.” (Source: Photograph source: www.megalithic.co.uk. Generously provided by the courtesy of Mr. Hatsuki Nishio.)
It turns out the stones mark the high water lines of previous tsunamis, some dating back as far as 869 AD. Although none of the stones is believed to be quite that old, it is thought that many of the current stones are replacements for much older predecessors; literally a monumental effort by subsequent generations to keep the lifesaving message alive in perpetuity.
Modern Japanese ignore these stones at their own peril. The people of Aneyoshi listened to their stone and their village survived the March 2011 tsunami. But people in some other villages thought the construction of modern seawalls provided sufficient protection and that warnings on the stones had become obsolete. The 2011 tsunami, however, crested most seawalls, and the villages with buildings below their stone paid a heavy price for ignoring their ancestors.