Decades after weapons testing stopped, researchers are still struggling to decipher the health impacts of radiation exposure around Semipalatinsk.
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Other traces of the past are harder to see. Folded into the city’s history — into the very DNA of its people — is the legacy of the cold war. The Semipalatinsk Test Site, about 150 kilometres west of Semey, was the anvil on which the Soviet Union forged its nuclear arsenal. Between 1949 and 1963, the Soviets pounded an 18,500-square-kilometre patch of land known as the Polygon with more than 110 above-ground nuclear tests. Kazakh health authorities estimate that up to 1.5 million people were exposed to fallout in the process. Underground tests continued until 1989.
Much of what’s known about the health impacts of radiation comes from studies of acute exposure — for example, the atomic blasts that levelled Hiroshima and Nagasaki in Japan or the nuclear disaster at Chernobyl in Ukraine. Studies of those events provided grim lessons on the effects of high-level exposure, as well as the lingering impacts on the environment and people who were exposed. Such work, however, has found little evidence that the health effects are passed on across generations.
People living near the Polygon were exposed not only to acute bursts, but also to low doses of radiation over the course of decades (see ‘Danger on the wind’). Kazakh researchers have been collecting data on those who lived through the detonations, as well as their children and their children’s children. The effects aren’t always obvious or easy to trace. But researchers are now starting to see some subtle impacts that linger 30 years after the Polygon closed. Studies show elevated risks of cancer, and one published in the past year suggests that the effects of radiation on cardiovascular health might be passed down from one generation to the next.
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People living near the Polygon were exposed not only to acute bursts, but also to low doses of radiation over the course of decades (see ‘Danger on the wind’). Kazakh researchers have been collecting data on those who lived through the detonations, as well as their children and their children’s children. The effects aren’t always obvious or easy to trace. But researchers are now starting to see some subtle impacts that linger 30 years after the Polygon closed. Studies show elevated risks of cancer, and one published in the past year suggests that the effects of radiation on cardiovascular health might be passed down from one generation to the next.
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In 1991, following Kazakhstan’s independence from the Soviet Union, officials from Moscow sent a special committee to Semey to open up the dispensary. Some records were destroyed. Other classified files were returned to Moscow. Even today’s researchers are unaware of what those records contained. The dispensary was renamed the Scientific Research Institute of Radiation Medicine and Ecology (IRME), which inherited the remaining classified health-data files. In addition to continuing epidemiological studies on the effects of nuclear radiation on human health, the IRME has a small clinic for treating people whose family members were affected by tests, and a mobile medical unit.
Over the years, those who sought care from Dispensary No. 4 or the IRME were logged in the state’s medical registry, which tracks the health of people exposed to the Polygon tests. People are grouped by generation and by how much radiation they received, on the basis of where they lived. Although the registry does not include every person who was affected, at one point it listed more than 351,000 individuals across 3 generations. More than one-third of these have died, and many others have migrated or lost contact. But according to Muldagaliev, about 10,000 people have been continually observed since 1962. Researchers consider the registry an important and relatively unexplored resource for understanding the effects of long-term and low-dose radiation2.
Geneticists have been able to use these remaining records to investigate the generational effects of radiation. In the late 1990s, Kazakh researchers went to Beskaragai, a town in the periphery of the Polygon that had been heavily irradiated. They collected blood samples from 40 families, each spanning three generations, and sent them to Yuri Dubrova at the University of Leicester, UK, for analysis. Dubrova, a geneticist, specializes in studying the impact of environmental factors on the germ line, the DNA found in sperm and eggs that can be passed on to offspring. He was intrigued to study the Polygon families, to start unpicking the appearance of mutations across generations.
In 2002, Dubrova and his colleagues reported that the mutation rate in the germ lines of those who had been directly exposed was nearly twice that found in controls3. The effects continued in subsequent generations that had not been directly exposed to the blasts. Their children had a 50% higher rate of germline mutation than controls had. Dubrova thinks that if researchers can establish the pattern of mutation in the offspring of irradiated parents, then there could be a way to predict the long-term, intergenerational health risks. “That’s the next challenge,” he says. “We think techniques like next-generation sequencing could potentially provide us with real information about the impact of human mutations.”
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The difference could come down to the pattern of exposure. With long-term, low-dose radiation, cells will accumulate mutations as they constantly try to repair the damage done to their DNA. Bernd Grosche, a retired radiation epidemiologist formerly with Germany’s Federal Office for Radiation Protection in Oberschleissheim, says that’s why it is important to look at populations that have received different kinds of exposure, to understand the full extent of the effects on human health. With the availability of the registry in Kazakhstan, Grosche says, it would be negligent not to analyse it.
But studying environmentally exposed populations is challenging, says Cari Kitahara, a cancer epidemiologist at the National Cancer Institute in Bethesda, Maryland, mostly because of the need to collect detailed exposure data on a large number of individuals. Kitahara is studying the effects of radiation on the health of medical radiation technicians, in whom exposure is easier to track. Others are studying uranium miners and nuclear workers, who are exposed to low doses of radiation over time. Whereas many radiation technicians are women, and most miners and nuclear workers are men, the Polygon population is remarkable in that it represents the general population.
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