Chernobyl's Legacy

T. SUESS/TIMMSUESS.COM T.

Ghost from the past: encased in crumbling concrete, the deadly contents of Chernobyl’s reactor number 4 still exert a far-reaching effect on the area.

Despite those differences, the quarter-cen- tury of work following the Chernobyl disaster will offer some important lessons for Japan Chernobyl’s legacy as the nation begins to assess the health and environmental consequences of Fukushima. Twenty-five years after the nuclear disaster, the clean-up grinds The problems that followed Chernobyl also on and health studies are faltering. Are there lessons for Japan? provide a grim reminder about the value of accurate information. Officials need to tell people immediately how to avoid the initial, BY MARK PEPLOW most dangerous, exposure; yet in the longer term, scientists and the government must bat- tle against unnecessary concern over low-level he morning train from Slavutych the ensuing blaze spewed 6.7 tonnes of material doses of radiation, which often causes more is packed with commuters playing from the core high into the atmosphere, harm than the radiation itself. cards, browsing e-readers, or watch- spreading radioactive isotopes over more than In some ways, the connection between the ing the monotonous flood plains pass 200,000 square kilometres of Europe (see ‘The two accidents may yield the biggest benefits Tby. It looks like any other routine journey to hottest zone’). Dozens of emergency workers for Chernobyl. For a brief window of time, the work. But rather than facing a crush through died within months from radiation exposure world has again focused attention on the largely subway turnstiles at the end of the 40-minute and thousands of children in the region later overlooked work there. The renewed interest trip, the workers are met by a row of full-body developed thyroid cancer. The region around may spur nations to chip in the cash needed to radiation monitors. It is the start of another day the plant became so contaminated that officials complete the clean-up of the site, and to carry at the Chernobyl power plant, the site of the cordoned off a 30-kilometre exclusion zone that out health studies that have languished for want world’s worst civilian nuclear disaster. straddled Ukraine’s border with Belarus. Today, of proper coordination and funding. “In recent As the train trundles through the bleak a staff of about 3,500 enters the zone each day to years, Chernobyl has been neglected by fund- Ukrainian countryside, another nuclear crisis monitor, clean and guard the site, where reme- ing agencies and, to an extent, the scientific is unfolding halfway around the world. Barely diation work will continue for at least another community,” says Jim Smith, a radioecologist a week after the partial meltdown at the Fuku- 50 years (see ‘Half-life of a disaster’). at the University of Portsmouth, UK, who has shima Daiichi nuclear power station, it is no So far, the Fukushima accident is less severe. studied the consequences of the accident for surprise that some of the chatter on the train Radiation levels measured near the Japanese 20 years. “But there is still more to learn from turns to the incident there. “It looks bad,” says power plant have been less than those at Cher- Chernobyl about decommissioning and the one commuter. “But not as bad as Chernobyl,” nobyl after the blast there (see ‘Exposure in con- effects of the radiation,” says Smith, who is he adds, with a hint of grim pride. text’). And although radiation has spread from touring the site with a group of other scientists. When Chernobyl’s reactor number 4 Fukushima, it does not match the amounts that After clearing a security checkpoint, the exploded in the early hours of 26 April 1986, rained down in the region around Chernobyl. visiting researchers board a bus that heads

562 | NATURE | VOL 471 | 31 MARCH 2011 © 2011 Macmillan Publishers Limited. All rights reserved HALF-LIFE OF A DISASTER towards the heart of the ageing power plant. waste — partly because of persistent flooding Owing to a awed safety test, They pass abandoned buildings and bump in some of the waste-storage buildings and 986 Chernobyl's reactor 4 explodes, along potholed roads running beneath arch- reactor 4’s turbine hall. Every month, at least scattering debris from the core ways made of piping; since the accident, pipes 300,000 litres of radioactive water must be 26 APRIL over a wide area. have been laid above ground to avoid disturb- pumped out of the structures and stored on site. ing contaminated soil. The main cause of this flooding is Cherno- 27 APRIL The visitors stop to look at the most visible byl’s brimming cooling pond, which artificially A day after the reminder of the accident, the concrete sar- elevates groundwater levels in the area. Alex- blast, some 44,000 residents are cophagus that entombs the shattered reactor ander Antropov, a Chernobyl veteran with evacuated from building. Completed hastily in November ice-blue eyes and a cool manner to match, is Pripyat, just 3 km from the reactor.

AKG-IMAGES/RIA NOWOSTI AKG-IMAGES/RIA 1986, the sarcophagus was built to contain the in charge of a project to decommission the escaping radiation, but it is now crumbling and pond. The term ‘cooling pond’ usually refers streaked with rust. Smith whips a dosimeter to the containers where spent fuel rods are 5 MAY The re in the reactor is nally out of his rucksack and poses for a photograph stored until their radiation dissipates enough extinguished, having released 6.7 tonnes of radioactive material in front of the sarcophagus. The reading is that they can be put into long-term storage. over 200,000 square kilometres. 5 µSv h−1: about 10 minutes of exposure at that But Chernobyl’s pond is actually a vast reser- level equals the same dose as an arm X-ray. voir covering 22 square kilometres into which People and cattle are evacuated from a The plant’s bright main office is a stark con- water from the reactor cooling systems was 6 MAY 30-kilometre exclusion zone around the trast to the sarcophagus. Stained-glass win- discharged. The pond also contains long-last- plant. dows depict — in glorious socialist–realist ing radioactive material such as caesium-137 style — the harnessing of atomic energy. But and strontium-90, which rained down after 4 months after the blast, 28 emergency AUGUST workers have died from acute radiation the plant has not produced power since 2000, the explosion. Besides causing flooding at the sickness, caused by massive doses of when the last reactor was shut down. Valeriy plant, the high water levels in the cooling pond radiation. Seyda, a deputy director of the Chernobyl raise the risk that a weak dyke along its east Nuclear Power Plant, explains that the plant’s side will burst, which would send water cours- top priority now is to construct a new confine- ing into the Pripyat River. Radioactivity in the NOVEMBER Workers complete ment shelter for reactor 4 before the sarcopha- escaping water would be quickly diluted by the a concrete gus becomes too unstable. If it collapses before river, so although it would not significantly sarcophagus the new shell is in place, it could throw up a raise exposure levels for people downstream, it around the cloud of radioactive particles and expose the could cause panic among the local population. shattered reactor I. KOSTIN/SYGMA/CORBIS to limit further deadly remnants of the reactor. Antropov says that his team cannot simply release of radiation. lower the water levels in the pond because they REPLACING THE RUSTING TOMB don’t know what effect microscopic radioactive Cases of thyroid cancer in local children The plan is to build an enormous steel arch sediment particles would have if exposed. In 99 have risen ten-fold from previous levels. adjacent to the reactor and slide it along a run- the meantime, the team maintains the status way to cover the building. The arch will reach quo by pumping water from the Pripyat River 105 metres high, with a span of 257 metres — into the pond at a cost of a few hundred thou- the world’s largest mobile structure, according sand euros per year. But the long-term plan is 2000 to its designers. It is expected to be in place to lower the water level by 7 metres to form a The last of Chernobyl's reactors is switched o. by 2015 and should last for 100 years. It will patchwork of 10–20 smaller ponds that would enable robotic cranes inside to dismantle the keep the most dangerous sediments in place. sarcophagus and parts of the reactor. Long- The project would cost €3 million to €4 million, term plans call for finishing the clean-up work says Antropov. He is already in discussions with The United Nations Chernobyl Forum K. DIORDIEV/REUTERS/CORBIS at Chernobyl by 2065. the relevant regulators and is optimistic that the 2005 reports that no more than 4,000 people Some of the concrete trenches for the necessary feasibility studies and environmental will die from the reactor's fallout. project are in place. But the international impact assessments can be completed. Chernobyl Shelter Fund that supports the But the effort has been a long time coming. 25th anniversary conference expects to US$1.4-billion effort still lacks about half of The decommissioning plan is more than a dec- 20 see lobbying for more funds for that cash, and the completion date has slipped ade old, and was supported by a 2005 survey clean-up and health studies. by almost ten years since the shelter plan was for the European Commission, led by Smith. IDÉ/VINCI agreed in principle in 2001. One of the key Once again, money has been a key factor in the goals of a forthcoming conference — Cher- delay. The major parts of Chernobyl’s decom- 20 5 nobyl, 25 Years On: Safety for the Future — to missioning plan are paid for by international New safe connement be held in Kiev on 20–22 April is to secure funds, but the cooling pond project is not. Nor shelter projected to be completed. more cash commitments from international is the research needed to satisfy the regula- donors. Meanwhile, Chernobyl is developing tors. “Most of our own activities come from long-term storage facilities for the debris that the Ukrainian budget, and we are not a rich

M. PEPLOW will be hacked out of reactor 4; and for more country,” says Seyda. 2020 than 20,000 spent fuel canisters from the site’s After leaving the cooling pond, the visi- Remediation eorts at other reactors, a facility that will cost about tors stop at Pripyat, an abandoned town just plant’s cooling pond scheduled to be €300 million (US$420 million). 3 kilometres from the reactor complex. Some completed. Although all those 44,000 residents were evacuated the day after NATURE.COM reactors have been shut- the accident, and many of their belongings still For a slideshow and tered, the plant contin- litter the decaying buildings. Antropov once Planned completion of clean-up other extras see: ues to generate large lived here — his daughter was a few months 2065 at Chernobyl. go.nature.com/bmliu6 amounts of radioactive old at the time of the accident — and as deputy

31 MARCH 2011 | VOL 471 | NATURE | 563 © 2011 Macmillan Publishers Limited. All rights reserved NEWS FEATURE THE HOTTEST ZONE Shifting wind patterns carried radiation from the Chernobyl Today, hundreds of farms Radioactivity from Chernobyl blast across much of Europe (right). Plant operators are now in Wales still have their was rst detected in western trying to lower water levels in a massive cooling pond (below) sheep tested for Chernobyl Europe by monitoring lled with radioactive water and sediments. radiation before herds can equipment at Forsmark nuclear be moved or sold. power station in Sweden.

CHERNOBYL NUCLEAR POWER PLANT RUSSIA

PRIPYAT TOWN COOLING POND BELARUS CHERNOBYL UKRAINE IMAGE CREATED BY J. ALLEN USING EO-1; SOURCE: NASA EO-1 TEAM SOURCE: NASA EO-1 J. ALLEN USING EO-1; BY CREATED IMAGE

RED FOREST PRIPYAT RIVER Caesium-137 levels (kBq m–2) in 1986 Alpine regions were among Kilometres the most contaminated areas 0 2 5 10 CHERNOBYL TOWN outside the former USSR. 1,480 185 40 10 2 No data chief of the town’s Communist party office, National Cancer Institute (NCI) in Bethesda, epidemiologist at the Centre for Research in he was responsible for evacuating part of the Maryland. The latest results from the Ukrain- Environmental Epidemiology in Barcelona, town. Because he worked as a senior engineer ian section of this cohort1 confirm previous Spain. “Some think they are doomed because at the nuclear plant, he knew that the disaster findings that the incidence of thyroid cancer is of their radiation exposure.” Further research would have repercussions for decades to come. proportional to the size of the dose, with a par- could provide convincing evidence that Cher- “I understood that I would never return to live ticularly high risk seen in younger people and nobyl’s radiation did not significantly harm the in Pripyat,” he says, in an uncharacteristically in those who were iodine-deficient due to poor wider population, but “we won’t know unless soft voice. “I still feel some sense of loss.” diet. The research is having a direct impact in we look”, says Dillwyn Williams, a cancer The evacuees from Pripyat also live with Japan, where those at risk of exposure are being researcher at the Strangeways Research Labo- lingering fear about the radiation they were given potassium iodide tablets to prevent the ratory in Cambridge, UK. exposed to before fleeing their homes. Along uptake of radioiodine in their thyroid. A handful of Chernobyl studies have found with millions of others from the surround- The NCI oversees a second cohort made small increases in rates of breast cancer and ing regions, they often attribute any sign of up of liquidators, a group of more than half a cardiovascular disease, but they did not prop- ill health to the accident. But pinning down million people sent into the exclusion zone to erly account for confounding factors, such as Chernobyl’s true public-health impact has help clean up and monitor the area after the nutrition, alcohol consumption and smoking proved remarkably difficult. initial emergency phase of the accident. Liqui- habits. And although some researchers have There is little disagreement about the terrible dators have a slightly raised risk of developing claimed to see an increase in genetic mutations fate of the workers who brought Chernobyl’s cataracts, and possibly a small increased risk in the children of parents irradiated after Cher- stricken reactor under control. Of 134 emer- of leukaemia2. nobyl4, there has been no similar evidence of gency workers diagnosed with acute radiation hereditary effects even in the children of Japa- sickness, 28 died from their exposure within LONG-TERM EFFECTS nese atomic bomb survivors, who on average four months. Another 19 have died since from But what was the impact on the wider popu- received much larger radiation doses. various causes, and many of the surviving lation? Various studies have tried to estimate This means that there is still a substantial workers now have cataracts and skin injuries. how many deaths Chernobyl will eventually gap in the overall understanding of Cherno- More than 5,000 cases of thyroid cancer have cause across the whole of Europe, but their byl’s health effects, says Williams. The prob- so far been seen in people who were children answers range from a few thousand to hun- lem is exacerbated by the piecemeal nature of at the time of the accident and lived in con- dreds of thousands3. Cancer causes about a previous studies. “There has been a failure of taminated areas of the former Soviet Union quarter of all deaths in Europe, so teasing out European-level coordination on this,” he says. — a more than ten-fold increase from normal Chernobyl’s far-reaching influence would Williams hopes that there is now a chance to levels (adults were mostly unaffected by the probably be impossible, say epidemiolo- establish a Chernobyl Health Effects Research disease). Most of these cases were caused by gists. Moreover, focusing on such intangible Foundation, which would mirror the highly drinking milk contaminated with radioiodine. numbers can distract from the much broader effective Radiation Effects Research Founda- Fewer than 20 of these people have died, but social impact of the accident. In Ukraine and tion that monitors the long-term health impacts the sheer number of cancers, and their rapid Belarus, hit hard by the break-up of the Soviet of the atomic bombs in Japan. Together, the onset within 5 years of the accident, surprised Union in 1991, lingering fears about radia- efforts could reveal the differences between many epidemiologists. tion are thought to have contributed to a sense the single short-term dose of external radiation This triggered a plethora of thyroid stud- of hopelessness that is linked to high rates of delivered by the atomic bombs, and the low- ies, most notably a long-term cohort study alcoholism and smoking — factors that have a level long-term exposure seen after Chernobyl. of 25,000 people in Ukraine and Belarus who much bigger health impact. Long-term doses were once thought to carry were children in 1986 that is being coordi- “There’s tremendous uncertainty for these much less risk than the immediate exposure, nated by the US National Institutes of Health’s people,” says Elisabeth Cardis, a radiation but evidence is accumulating that the risks

may be much the same5. If confirmed, it would access to medical records in Ukraine and more real health legacy. “I have a house in a village mean that people routinely exposed to low- information about participants’ lifestyle factors near Slavutych, on contaminated territory,” level radiation have a greater chance of health — both potentially tall orders. says Antropov during the site visit. “Two of problems than previously thought. The ARCH plan will be presented at the 25th my neighbours died of cancer, and this was The European Commission has funded anniversary conference in April, and Cardis probably the result of their radiation doses.” Williams, Cardis and a core group of other hopes that a positive reception will prompt the scientists to develop a research plan, dubbed European Commission to boost its support. LESSONS FOR JAPAN the Agenda for Research on Chernobyl Health It is likely to be difficult to secure a long-term It’s too early to say how the Chernobyl health (ARCH), that maps out how the existing commitment for the studies, which will cost studies will help those affected by the Fukush- cohorts could be used to study a wider range about €3 million to set up, but that cost is minor ima accident. But Chernobyl has already given of diseases, such as breast cancer and cardio- compared with the billions that will be spent on the world a lasting lesson on the importance of vascular disease, and to address the questions remediation at Chernobyl, says Williams. clear communication during a nuclear disaster, about the long-term effects of low doses. The Beyond obtaining the necessary funds, and in the years afterwards. liquidator cohort, for example, is six times researchers will also require cooperation There was no systematic distribution of pro- larger than that of atomic bomb survivors, with from participants to expand the cohort stud- phylactic potassium iodide to the people around a much wider range of exposure doses. It could ies. That could be difficult. Gennady Laptev, Chernobyl, and Pripyat’s children were allowed show how risk varies over that large range of now a hydrologist based at the Ukrainian to play outside during the day after the accident, doses and uncover rarer effects at lower doses. Hydrometeorological Institute in Kiev, was while the reactor continued to burn. “The fail- It could also help to reassess the threshold dose a liquidator for three years, and says that he ure to rapidly communicate radiation risks at to prevent nuclear workers from developing stopped attending his medical check-ups about Chernobyl led to people receiving higher radia- problems such as cataracts. ten years ago because they were too time-con- tion exposures than was necessary,” says Smith. ARCH also suggests testing the feasibility suming. “They never found any major health The Japanese government has been lam- of setting up new cohorts including liquida- problems,” he says. basted for not keeping citizens well informed tors’ offspring and highly exposed evacuees, Laptev’s work involved flying by helicopter about the accident there. But it was swifter to along with a tissue bank. The bank may reveal from Kiev to Chernobyl twice a week to take act than Soviet officials were, ordering the whether people’s genetic make-up influences radiation readings and collect soil and water evacuation of people who live near the plant their susceptibility to radiation — key infor- samples for analysis. “Nobody forced me to within hours of recognizing the growing mation for determining how individuals are do the work — I did it because it was interest- nuclear emergency, and expanding that evacu- likely to respond to the radiation received during, and I really enjoyed it,” he says. But after ation zone to a radius of 20 kilometres the fol- ing medical procedures such as X-ray scans three years, he became worried about the risk lowing day. As well as distributing potassium and radiation treatment. of working near the plant, so he took a job iodide, the Japanese government banned the There are several hurdles, however, to get- researching how radioisotopes dispersed in sale of food and milk produced in the prov- ting ARCH off the ground. The project needs the local water system. inces around the stricken plant. “The Japanese support from the NCI, which stopped funding Concerns about radiation exposure con- have done exactly the right thing,” says Andrew active clinical monitoring of the thyroid cohort tinue to plague residents in the region, and the Sherry, director of the Dalton Nuclear Institute in 2008 because of budgetary constraints. And planned studies could provide the answers at the University of Manchester, UK. ARCH’s proposals would also require better they so desperately need about Chernobyl’s Ultimately, says Smith, Chernobyl’s most important lesson for Fukushima is that a nuclear accident haunts a region long after the reactors have cooled. If areas of Japan are “Some think they are doomed because significantly contaminated with radioactive caesium-137, which loses half its radioactivity of their radiation exposure.” in 30 years, the government may have to main- tain an exclusion zone for decades. Decommis- sioning the Fukushima reactors may also take EXPOSURE IN CONTEXT decades, depending on the extent of damage to Many emergency workers at Chernobyl received lethal doses of radiation, but the broader public, even their cores. And the uncertainty surrounding those living in the contaminated zone, were exposed to levels on a par with some medical procedures. the health risks may exact a psychological toll Dose (mSv) Source/implication that could surpass the physical harm from the Up to 5,000 One minute’s exposure to Chernobyl core shortly after explosion radiation, adds Smith. 1,000 Causes temporary radiation sickness, including nausea and decreased white-blood- Many of the workers at Chernobyl under- cell count stand those lessons all too well as they shuffle 250 Upper annual limit allowed for Fukushima emergency workers onto the train to Slavutych at the end of their 120 Average total dose received by liquidators at Chernobyl (1986–90) day. The workers will return to tend to the plant tomorrow and the next day — and for SOURCE: UNSCEAR/ WORLD NUCLEAR ASSOC. SOURCE: UNSCEAR/ WORLD 30 Average total dose of external radiation received by evacuees from Chernobyl plant ■ SEE EDITORIAL P.547 and surrounding area many years to come. 20 Average annual limit for nuclear-industry workers Mark Peplow is Nature’s news editor. 9 Total dose received by the 6 million residents in contaminated areas (>37 kBq m−2) in former USSR 1. Brenner, A. V. et al. Environ. Health Perspect. 9 One computed-tomography (CT) scan doi:10.1289/ehp.1002674 (2011). 2. Cardis, E. & Hatch, M. Clin. Oncol. doi:10.1016/ 9 Annual exposure of airline crew flying regularly between New York and Tokyo j.clon.2011.01.510 (2011). 3 One mammogram 3. Peplow, M. Nature 440, 982–983 (2006). 4. Dubrova, Y. E. et al. Nature 380, 683–686 (1996). 2.4 Average annual background radiation globally 5. Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2 (NRC, 2006); available 0.3 Total dose received by each resident of Europe for 20 years after Chernobyl at http://go.nature.com/r7jeca.