Chernobyl: History of a Nuclear Disaster and Health Impact

Decades Later, Chernobyl Is Still Linked to Thyroid and Other Health Effects

25 years after the Chernobyl disaster, the health effects are still felt in the former Soviet Union. Ezra Shaw / Getty Images News

On April 26th, 1986 at 1:23 am, things in Chernobyl, a tiny town in the Soviet countryside, went very wrong. Today the name "Chernobyl" is a touchstone, a single word that means "nuclear disaster" to people around the world. Chernobyl was, in fact, the worst nuclear accident in history. Even though the March 2011 Fukushima reactor accident was judged to be as "serious" as Chernobyl by nuclear authorities, it's thought that the radiation release in Japan was far less than in Chernobyl, and the fallout had less impact on other regions.

Still, it may be years before we know if Chernobyl will continue to hold the dubious distinction of being the world's worst nuclear disaster.

In any case, Chernobyl has been of particular interest to thyroid practitioners and patients, because one of the radioisotopes released during nuclear reactor accidents -- including the Chernobyl disaster -- is iodine 131, also known as radioactive iodine, or radioiodine.

Iodine 131 has a half-life of eight days, meaning that half of it disperses every eight days. This fairly long half-life (when you compare it to some radioisotopes, which have half-lives of seconds or minutes) means that radioactive iodine can quickly get into the human food supply by contaminating plants, animals, and water, and well before a significant amount of the radiation decays and disperses. Once ingested, radioactive iodine concentrates almost exclusively in the thyroid gland, where the radiation can cause either destruction of the gland, or act as a long-term trigger for the development of thyroid cancer and other thyroid problems.

Young children and fetuses, who have developed and fast-growing thyroid glands, are the most susceptible to exposure to radioactive iodine, and the effects of exposure also tend to show up more quickly in children compared to adults. Children also are the main consumers of milk, and when cows eat radioactive iodine-contaminated grass, the iodine concentrates heavily in milk, making milk consumption another key pathway for exposure to radioactive iodine.

It's important to review some history behind the Chernobyl crisis, and the health impact of the crisis, not only in on thyroid health, but other health effects as well.

Some Chernobyl Geography and Political History

The small town of Chernobyl is located in the province -- known as an "Oblast" -- of the Kiev district in Ukraine. In 1986, Ukraine was a state of what was still the Soviet Union. Chernobyl is located 110 miles from Kiev, 22 miles from Ukraine's border with the Gomel Oblast of Belarus, and near the Bryansk Oblast of Russia. The Chernobyl region was primarily an area populated by small-town farmers.

The nuclear plant, originally built as part of the Soviet Union's nuclear weapons program, was located two miles outside of the main part of the town of Chernobyl itself. The reactor was located at the junction of two rivers, the Pripyat and Uzh, near the Kiev reservoir, which provided a plentiful supply of water for cooling. Over time, the plant was converted for use as a civilian power station.

The official Soviet policy was to minimize information dissemination or discussion of problems related to the construction, maintenance, and operating procedures at nuclear plants. We now know that as a result of this narrow-minded thinking, throughout the former Soviet Union, there was minimal training, disaster drills, and preparedness for nuclear emergencies, and Chernobyl was no exception. The Soviet Union also operated under a political system that left Moscow with tremendous power over its various republics and regions, so the Chernobyl region, as part of Ukraine, was under the political rule of decision makers thousands of miles away in Moscow.

As a result, when the nuclear disaster struck at Chernobyl, not only were the plant's staff and the region's residents unprepared to respond appropriately to a nuclear accident, but the response was stalled, as local officials waited for direction from Moscow. It has been reported that even as radiation leaked from the crippled reactor, children were being sent to school, an outdoor wedding was held, a soccer match took place, and local residents went fishing in the nuclear plant's cooling ponds.

According to United Nations reports (1), it was actually two full days -- after one reactor had already blown up, and a second was on fire -- before Moscow even acknowledged that "something" had happened in Chernobyl, much less revealed the magnitude of the disaster.

What Did Happen at Chernobyl?

The International Atomic Energy Agency has described what happened to cause the Chernobyl nuclear disaster. Reportedly, while workers were conducting a test of Reactor Four, a huge power surge hit the Chernobyl plant , resulting in an explosion and fire, which released a huge plume of radiation into the atmosphere. The design of the Chernobyl reactors was considered outdated, and had no containment structure to protect the surrounding area from leaked radiation. Reactor Four's explosion released more than 100 different radioactive elements into the environment.

Two workers at the plant were killed immediately. Many of the first responders were reported to have died very soon after they responded to the accident, and most within three months of the initial explosion. Helicopter pilots who worked at the site in the early days ended up being airlifted to Moscow for treatment within days and weeks of helping to contain the accident.

In the earliest days, approximately 49,000 immediate residents were evacuated from the area, but were told they would be displaced for only two or three days.

In the following weeks, more explosions occurred, but the risks to the region were denied or minimized. Soviet officials did not even acknowledge some of the subsequent blasts at the plant, and were assuring the public that the situation had totally stabilized and that radioactive levels in the area were normal.

By May of 1986, a month after the disaster, more than 116,000 people in the surrounding 18-mile area had been relocated. In coming years, the number of people who were ultimately displaced was estimated to be approximately 230,000, according to the U.S. Nuclear Regulatory Commission.

We now know that a much wider geographic area was actually exposed to the radiation from Chernobyl. In a 2006 report from GreenPeace called The Chernobyl Catastrophe: Consequences on Human Health, an international panel of scientists, many outstanding experts in their fields and others who were long-time researchers who had been monitoring Chernobyl since 1986, commented:

This truly global event had its greatest impacts on three neighboring former Soviet republics, namely the now independent countries of Ukraine, Belarus, and Russia. The impacts, however, extended far more widely. More than half of the caesium-137 emitted as a result of the explosion was carried in the atmosphere to other European countries. At least fourteen other countries in Europe (Austria, Sweden, Finland, Norway, Slovenia, Poland, Romania, Hungary, Switzerland, Czech Republic, Italy, Bulgaria, Republic of Moldova and Greece) were contaminated by radiation levels above the limit used to define areas as "contaminated." Lower, but nonetheless substantial quantities of radioactivity linked to the Chernobyl accident were detected all over the European continent, from Scandinavia to the Mediterranean, and in Asia. (2)

Back at Chernobyl itself, teams of what were referred to as "liquidators" were brought in to help contain the radiation, remove debris, and ultimately, to help build a giant concrete structure -- called the "sarcophagus" -- to seal off the reactor.

A team of 250,000 construction workers, who are all said to have been exposed, in several months, to a lifetime limit of radiation, took part in what is considered the largest engineering project in history, and by the end of 1986, they had entombed the Chernobyl reactor in the sarcophagus.

The Health Effects of Chernobyl

How many people suffered health effects from Chernobyl?

It is actually quite difficult to quantify the extent of damage to human health and the environment. The information varies, depending on whether it comes from the Soviet government at the time of the accident, current governments, international agencies, or independent groups.

According to a United Nations report:

Of the casualties from Chernobyl, 35 people were declared to be in a "serious condition," and six had died. The toll rose to 31 by the summer of 1986, and there it remained. None of the many officially corroborated direct victims of Chernobyl were ever added to this list: their deaths were attributed to other causes. (3)

The US Nuclear Regulatory Commission has reported that studies show residents of the region did not receive doses of radiation strikingly higher than normal, and that no increased rate of cancer has been detected . They have reported that only children have shown an increase in thyroid cancer -- 4,000 additional cases to be specific -- and that 99% of those cases have been "cured." (4)

Both official accounts seem underplayed. A case in point is the report from the UN's Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), which noted that as of 2005, more than 6,000 Russian, Ukrainian and Belarussian citizens were diagnosed with thyroid cancer.(5)

In any case, the need to remove a child's thyroid gland due to cancer can hardly be seen as a "cure" in the sense of the word. The children of Chernobyl have been, and will continue to be saddled with health issues as a result of their thyroid "cure" throughout their lifetimes, and some experts believe that the genetic effects may carry on into the next generation. From Harvard University, a study published in Environmental Health Perspectives looked at the incidence of thyroid cancer from radioactive iodine 131 in over 12,000 Ukrainians over 18 who were exposed to radiation during Chernobyl. The population was screened up to four times between 1998 and 2008, and the researchers found the following:

  • There was an increased risk of thyroid cancer 20 years after the initial exposure. This risk was not uniform for the whole group and seemed to be most dependent on the geographical distance from the plant at the time of exposure.
  • The increased risk of thyroid cancer was, on average, 1.91 times higher for every additional gray of radiation exposure. (A gray equals the absorption of one joule of ionizing radiation per one kilogram of tissue).
  • There is no evidence indicating that this increased cancer risk for those who lived in the area at the time of the accident is decreasing over time.

The report also said, "Previous studies of atomic bomb survivors have shown that even 30 years after the initial radiation occurs, increased cancer risks exist and do not significantly decline until after this point." (6)

In 1989, Time Magazine carried a story about the continuing cover-up around Chernobyl, particularly with regard to children who remained in the area, and were exposed to radiation over a prolonged period of time. The story quotes a variety of former politicians and scientists, who accused the Soviet government of downplaying the exposure levels -- they believe it was actually 20 times higher than reported -- as well as the evacuation schedule for those in the radioactive plume's direct path.

Said one official, "the evacuation of children was finished only on June 7. Little wonder that there are so many sick children in our district, especially those with hyperplasia of the thyroid gland." The story went on to note that this and other radiation-related disorders, like leukemia, have allegedly been misreported as more innocent sounding conditions. (7)

The advocates at GreenPeace have a much less optimistic view. In their 2006 Chernobyl Catastrope report, they detailed a much wider extent of destruction, finding that while official reports state that about 4,000 people more than average have died in Belarus, Ukraine and Russia since the accident, the experts involved in compiling the GreenPeace report identified at least 200,000 deaths out of the norm for the same population.

The GreenPeace report also pointed out that:

  • Among Belarussian liquidators -- the people who helped clean up the accident -- incidences of kidney, urinary/bladder and thyroid cancer were all significantly higher for the period from 1993 to 2003 versus a comparable reference group. Leukemia was significantly higher in liquidators from Ukraine, in adults in Belarus and in children in the most contaminated areas of Russia and Ukraine.
  • Among liquidators in general, some 88% showed evidence of chromosomal changes in their white blood cells.
  • From 1995 onward, excesses of cancers of the stomach, lungs, breast, rectum, colon, thyroid gland, bone marrow and lymph system have also been detected in the southwestern areas of the region. In the Tula region, unusually high rates of bone cancer and cancers of the central nervous system were detectable in children during the period from 1990-1994.
  • There was extensive exposure of the respiratory systems to radioactive materials released in gas form during the Chernobyl accident. Ukrainian Ministry of Health statistics documented a rise in chronic bronchitis and emphysema from around 300 per 10,000 population in 1990 to over 500 per 10,000 in the adult and adolescent population in 2004. Over the same period bronchial asthma morbidity almost doubled, reaching 55.4 cases per 10,000 population.
  • Between 1988 and 1999, early atherosclerosis and coronary heart disease became 10 to 15 times more common in evacuees from the 18-mile zone around Chernobyl, and those living in radiation-polluted areas, as compared to the general population.
  • Endocrine system disease, nutritional disorders, metabolic disease, and immune disorders were more than twice as common among evacuees from the 18-mile zone and those who were in the contaminated territories, as compared to the entire Belarussian population.
  • In the Chernobyl-affected territories of Russia, there was a five-fold increase in lowered immunity. In particular, reduced numbers of white blood cells were seen, along with reduced activity of T-lymphocytes and killer cells, and a higher incidence of diseases like thrombocytopenia and anemia.
  • A study of a number of Ukrainian residents before and after the Chernobyl accident revealed a six-fold increase in the frequency of radiation-induced chromosomal changes, a phenomenon which also seems to be carried over to their children. Chromosomal aberrations thought to be attributable to Chernobyl have been recorded as far away as Austria, Germany and Norway.
  • Even comparatively low levels of radiation can lead to some level of damage to the central and peripheral nervous systems. It's difficult to assess the full extent of neurological damage from Chernobyl's radiation, but liquidators from Russia, reported neurological diseases as the second most common post-Chernobyl illness. Neurological and psychiatric disorders among adults in radiation-contaminated territories of Belarus were also considerably more common than those from non-affected areas (31.2% compared to 18.0%).

    Greenpeace is not the only group concerned about the health implications of Chernobyl. In an article published in the Journal on Environmental Health Perspectives, scientists from Moscow presented evidence showing that the nuclear releases were potentially as much as 26 times more than reported. According to the Moscow scientists, only 10 to 15% of the radioactive materials were actually still left to be sealed in the sarcophagus-like structure that entombed the damaged reactor, versus the 90% that had been reported by authorities. They concluded that the radiation exposure levels were, therefore, much greater than other scientists have assumed.

    While the World Health Organization (WHO) estimated the radiation exposure levels of people in neighboring regions, direct biological data contradicts WHO figures, showing that the rate of unstable and stable chromosome aberrations was about 10 to 100 times higher than would be expected, and consistent a much larger release of radioactivity than reported. Also, higher rates of death and malformations among newborns were seen in Germany, Poland, Central Europe, Turkey, and the former Soviet Union shortly after the Chernobyl explosion.

    Outside of the immediately affected areas of Belarus, Ukraine, and Russia, the fallout from Chernobyl had effects. According to researchers, more than 40% of Europe was polluted with Chernobyl fallout, and health effects ranging from chromosomal changes to congenital malformations and thyroid cancer were recorded in countries from Norway to Turkey.

    • To the west and south, from Germany through Croatia to Bulgaria and Turkey, increased malformations at birth were recorded in children who were exposed before birth. This included Down syndrome, which typically occurs in around 1 in 1,000 births, but was elevated in Western Europe and Scandinavia. A statistically significant increase in frequency was apparent in January 1987, corresponding to children conceived during the period of highest Chernobyl fallout (Sperling et al. 1994b). Children born in eastern Romania between July 1, 1986 and December 31, 1987 were also significantly more likely to suffer from childhood leukemia than those born either before or after this period.
    • In the eastern part of Austria in the weeks after the accident, vegetables such as spinach and salad vegetables were not allowed to be sold to the public. Milk, especially milk from the alpine regions, was contaminated for more than a year. In regions without precipitation, especially the eastern part of Austria, the radioactive iodine concentrations in the air were high during the one or two days during which the radioactive cloud passed over. Doctors in this regions reported that the number of people with thyroid diseases increased from 1990 onwards.
    • About 3,000 liquidators came from Armenia; eighty children of these men were studied and found to be in generally poor health, suffering conditions including secondary pyelonephritis, gastrointestinal problems, tonsillitis, hyperthermic convulsions and epilepsy. Only 15 children (27.3%) were described as "healthy in practice."
    • The Czech Republic received fallout resulting in high contamination levels, too. a study of thyroid cancer covering 247 million person-years found that between 1976 and 1990, thyroid cancer was rising at a rate of 2% per year. However, from 1990 onwards, the rate rose above a 2% increase per year.
    • Thyroid cancer was significantly elevated in northern England, with a particularly high rate in Cumbria, the area which received the most fallout from the accident.

      Poland took proactive steps to protect its people. Many people don’t know that Chernobyl was a territory of Poland for hundreds of years. Today, Poland’s response to Chernobyl is viewed as a the model for a successful, proactive public health response to a nuclear accident. After the Chernobyl accident, Poland distributed potassium iodide pills to millions of its citizens. These tablets saturated the thyroid gland with iodine, preventing absorption of the radioactive iodine by the Polish population after the Chernobyl accident. Researchers and epidemiologists believe this helped to prevent a spike in thyroid cancer like those seen in neighboring areas around Chernobyl.

      Chernobyl: Have Lessons Been Learned?

      Much of what we know today about how to protect a population in the event of a nuclear accident came at the expense of those who lived in Chernobyl. We know how to design and build reactors that are more likely to contain radiation in a total meltdown.

      From the thyroid health perspective, we also have a better idea of what to expect -– thyroid cancer rates rose in those who were unprotected by potassium iodide and also in those who drank milk contaminated by fallout.

      At the same time, as the doctors and researchers involved with the GreenPeace “Chernobyl Catastrophe” report noted: “In terms of a holistic understanding of the implications of a large-scale nuclear accident for human health, it seems that we are little further ahead than we were before the Chernobyl explosion 20 years ago.”

      That became evident after the March 2011 earthquake and tsunami in Japan, which triggered a meltdown at the Fukushima nuclear reactor. The Japanese disaster came a little less than 25 years to the day after Chernobyl. Yet even with a quarter-century more experience with nuclear power, in a country that relies extensively on nuclear power, Japan has showed erratic communication and management of the issue, inconsistent and often conflicting evacuation plans, and has suffered shortages of potassium iodide in some key regions. Meanwhile, around the world, there has been a lack of understanding about what potassium iodide can –- and can not -– do in a radiation emergency; there's been the stockpiling and hoarding of potassium iodide outside of Japan, potential contamination of seafood, and many other concerns that remain to be resolved. it’s not clear that many of the Chernobyl’s most valuable lessons have actually been learned.


      (1) United Nations University “The Long Road To Recovery: Community Responses to Industrial Disasters” edited by James Mitchell ©1996


      Researcher/writer Lisa Moretti contributed to this article.

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