Chernobyl Nuclear Accident Minimal Radiation Effects

Update 2010 Based on Recent Assessments



Although the 1986 Chernobyl nuclear-reactor accident resulted in destruction of the power plant, its reported medical consequences were vastly and irresponsibly exaggerated. Its long-term effects have not been radiological, but largely financial and unnecessary.

Among the 134 persons with acute radiation disease who received extremely high radiation doses, 31 died soon after the reactor breach — from overwhelming radiation exposure, excessive heat burns, and direct mechanical trauma.

Of 103 highly exposed survivors, 19 died before 2004 from a multitude of causes not exclusively caused by ionizing radiation. Eventually the remaining 84 will die — but not necessarily prematurely nor as an attributable consequence of the incident.

As for latent medical effects in the exposed population of Ukraine, Belarus and Russia, there do not appear to be any casualties that can be clinically confirmed: Contrary to hasty estimates and fears based on a premature theories of radiation effects at low radiation doses, the mortality rate among those exposed to radioactive fallout cannot be distinguished statistically from normal morbidity.
Compared with other energy sources, the Chernobyl reactor eruption resulted in far fewer human casualties than other types of industrial disasters.

Radiophobia, exacerbated by and after the accident, vastly and unnecessarily increased subsequent economic losses in the former Soviet Union and elsewhere in Europe.

Moreover, in the aftermath of the Chernobyl tragedy, radiophobia was stoked by arms-control advocates who used public fear of low-level radiation in order to encourage opposition to Cold War nuclear-weapons testing.

Introduction, Perspective, and Fundamentals

The Chernobyl excursion on 26 April 1986 was probably the worst possible catastrophe of a nuclear power station. It was the only such catastrophe since the advent of nuclear power in the 1950s. It resulted in a total meltdown of the reactor core, a vast emission of radioactive materials, and early deaths of 31 persons.

However, its broader physiological (medical) aftermath is disputable because of the lack of definitive, relevant symptoms and casualties — much, much less than originally expected.

Chernobyl’s impact was not medical, but an enormous political, economic, social, and psychological price  mainly due to deeply rooted fear of radiation. Radiophobia has been compounded by the so-called linear non-threshold (LNT) assumption: the still-unproven theory that known effects from high, quantifiable doses could be linearly extrapolated to corresponding effects at low, estimated doses.

The tragedy was a crucial event with major negative impact on interim nuclear-power growth, but it had a constructive effect on nuclear regulation, design, and operations. It has also provided invaluable lessons for improved nuclear safety and for realistic radiation-risk assessment.

A recent Chernobyl-aftermath re-examination by radiation-expert Zbigniew Jaworowski[1] reinforces the evaluation of fewer proven and expected fatalities. In order to present this Knol in a publicly convenient format, his published work on this topic has been somewhat paraphrased, supplemented, and rearranged.

One should keep in mind the following about an exposure-response or dose-response relationship: The effect on an organism caused by differing levels of exposure (or doses) to a stressor (such as radiation) changes with exposure time. This may apply to individuals (e.g.: a small amount has no observable effect, a large amount is fatal), or to large populations (e.g.: how many people or organisms are affected at different levels of exposure), and the response might not be linearly proportional to the dose.

Short-Term and Latent Effects of Chernobyl Accident Were Highly Exaggerated

Almost none of predicted and publicized detrimental medical effects have materialized in nearly a quarter of a century since the Chernobyl tragedy. While there were 31 proximate fatalities to operators and emergency workers, few – if any – latent medical effects can be definitively attributed to the reactor explosion.

As a matter of fact, because the incident lead to unnecessary suffering and pauperization of millions of inhabitants in contaminated areas, it demonstrated that the LNT hypothesis was counterproductive in application of protection measures and radiation-dose limitations. (In the absence of definitive epidemiological data on the effects of radiation at low levels, the assumption is made that small doses over time have similar medical effects as large doses in shorter periods of time.) 

Keep in mind that after more than a half-century, the LNT hypothesis about the effects of low doses and levels of radiation is still an unsupported and doubtful theory.

This more realistic perspective that has materialized about Chernobyl radiation health effects were apparent soon after the catastrophe, but the information was not then shared with the public. Even now, those responsible for the exaggeration have not issued retractions.

Nuclear Power Has Lower Comparative Risk Than Other Power Sources

In terms of fatalities per electricity-unit produced, based on Chernobyl’s operating history (9 years operation,  36 GWe-years total electricity, 31 early deaths),  the result is 0.86 deaths/GWe-year. This rate is lower than fatalities from most other energy sources.

Chernobyl fatalities were nearly 50 times lower than from hydroelectric stations (~40 deaths/GWe-year).

In terms of human losses, the accident in the Chernobyl nuclear power plant had comparatively few casualties compared with other major industrial catastrophes. In the 20th century more than ten such catastrophes have occurred, with several hundreds to many thousands of fatalities in each. For example, coal smog killed approximately 12,000 people in London, UK, between December 1952 and February 1953. The annual death toll from accidents in Chinese coal mines reached 70,000 deaths in the 1950s.

Up to 20,000 people perished in 1984 due to an eruption in a pesticide factory in Bhopal, India.  As many as 230,000 fatalities resulted in 1975 from the collapse of a hydroelectric dam on the Banqiao river in China.

But the political, economic, social, and psychological impact of Chernobyl was enormous and mostly negative.

Cold War Policies Influenced the Perception of Radiation

Fifty years ago, the United Nations Scientific Committee on the Effects of Atomic Radiation  (UNSCEAR) formulated a position on the overly conservative LNT radiation-effects extrapolation after an in-depth debate that was not without influence from the political atmosphere and issues of the time.

The Soviet, Czechoslovakian, and Egyptian delegations to UNSCEAR strongly supported the LNT assumption and used it as a basis for recommendation of an immediate cessation of nuclear test explosions. LNT was also supported by the Soviet Union during the later years of the Cold War, and this was consistent with similar thinking of American authorities, academics, and anti-nuclear activists.

During the height of the Cold War I too personally opposed nuclear-explosive testing, but because it was inconsistent with strategic arms-control.[2]  In the absence of proof to the contrary (which did not emerge until more recently), the LNT formulation could be considered prudent in estimating potential hazards. Now, however, LNT is clearly injudicious because of mounting conflictual evidence.

In 1958, UNSCEAR noticed that environmental contamination by nuclear explosions increased radiation levels all over the world and thus alleged that it posed new and unknown hazards for present and future generations: These potential hazards were then uncontrollable, and UNSCEAR declared that “Man may prove to be unusually vulnerable to ionizing radiations….” The international assessment went further, concluding that “even the smallest amounts of radiation are liable to cause deleterious genetic, and perhaps also somatic [deleterious bodily], effects.”[3]

This was not merely a passing observation in the report: It was — as stated – the major “general [conclusion that emerged] clearly from the foregoing part of [the UNSCEAR 1958] report.”[4]

Those sentences were seized upon by anti-nuclear interests and had an enormous impact in subsequent decades and have been repeated in a plethora of publications. Even today, more than a half century later, without ever being justified, the pronouncements are taken as an article of faith by the public.

In addition to the long-term legacy of overstated radiation effects, Chernobyl had a peculiar political fallout. Quoting Mikhail Gorbachev, USSR General Secretary in 1986, “The nuclear meltdown at Chernobyl … even more than my launch of perestroika, was perhaps the real cause of the collapse of the Soviet Union five years later.…”[5]

Irrespective of technical and historical underpinnings, radiophobia – especially that aggravated by the Chernobyl meltdown – had deleterious Cold War economic, political, and humanistic impact, some of which persists in the new millennium. Unfounded radiophobic attitudes are still found to this day in addressing, for example, benign medical uses of radiation, overhyped threats from so-called “dirty bombs,” and peaceful applications of nuclear power.

While former Cold War academics and environmental activists have by now reduced their clamor of anti-nuclear protest, they have not come forth with public admissions of flawed analysis based on revised information and experience.

Technical Weaknesses of LNT Radiation Hypothesis

LNT-based projections of thousands of late cancer deaths are in serious conflict with present-day observations regarding the general-population health in Russia: There is now a 15% to 30% deficit of solid cancer mortality among Russian emergency workers, and a 5% deficit in solid-cancer incidence among the population in most contaminated areas, despite LNT-based predictions to the contrary.

Radiation doses from Chernobyl dust were estimated and compared with natural doses by UNSCEAR panels. During the first year after the accident, the individual dose received by Northern Hemisphere inhabitants was less than 2% of the average natural dose. (See Table at the end of this Knol, “Significant Individual Radiation Dose Rates and Doses” based on Jaworowski’s compilation.)

During the forthcoming 70 years, the global population will receive total Chernobyl radiation approximately 0.1% of natural lifetime dose. The added radiation from Chernobyl is especially small compared to natural radiation in some parts of the world.

Rather than risk factors based on the LNT hypothesis, epidemiological observations should be a basis of realistic estimates of latent medical consequences from the Chernobyl radiation excursion. All too often, the LNT theory has led to overhyped and unsustained numbers.

The absurdity of the LNT formulation was brought to light when it was calculated in 1987 that 53,000 people Chernobyl tragedy would die of Chernobyl-induced cancer over the next 50 years.[6] Such a frightening death toll was derived simply by multiplying trifling Chernobyl doses in the United States by the vast number of people living in the Northern Hemisphere, compounded a cancer-risk factor based on epidemiological studies of 75,000 atomic bomb survivors in Japan. But A-bomb survivor data are irrelevant to such estimates because of differences in individual doses and dose rates: A-bomb survivors were flashed within less than a second by radiation doses at least 50,000 times higher than any U.S. inhabitants will ever receive over a period of 50 years from the Chernobyl fallout.

We have reliable epidemiological data for Japanese A- bomb survivors. But there are no such data for human exposure at the small Chernobyl dose rate spread over a half-century or so. The dose rate in Japan was considerably more than the Chernobyl dose rate in the United States. Extrapolating over such a vast span is neither scientifically justified nor epistemologically acceptable.

The most nonsensical, expensive and harmful action, however, was the evacuation of over 300,000 people from contaminated regions of the former Soviet Union, where the radiation dose from Chernobyl fallout was about twice the natural dose. The mass evacuation caused great harm to the populations of Belarus, Russia, and Ukraine. It led to psychosomatic disturbances, great economic loss, and traumatic social consequences.

According to the leading Russian authority on radiation protection, the mass relocation was implemented by the Soviet government under the pressure of populists, ecologists and self-appointed “specialists,” and it was done against the advice of the best Soviet scientists.

The really dangerous air-borne radiation dose rate on the day of the Chernobyl excursion covered an uninhabited area of only about 0.5 square km in two patches reaching up to a distance of 1.8 km southwest of the reactor. It didn’t last long, declining by a factor of 100 just 2 days later.

Actual Health Effects and Emotionally Induced Misconceptions

There were 28 fatalities among rescue workers and employees at the power station due to very high doses of radiation, and 3 deaths due to other reasons. Otherwise, the only real adverse health consequences of the Chernobyl catastrophe among approximately five million people living in the contaminated regions were the following: acquired psychosomatic afflictions that appear as diseases of the digestive and circulatory systems, and other post-traumatic stress disorders such as sleep disturbance, headache, depression, anxiety, escapism, “learned helplessness,” unwillingness to cooperate, overdependence, alcohol and drug abuse, and suicides. 

The “liquidators.” who were involved in fire-suppression and radioactive-cleanup operations — and thus accumulated larger radiation doses than the general population — have not had increased incidence of leukemia or other cancers.

These diseases and disturbances in the general population could not have been due to the tiny irradiation doses from the Chernobyl fallout; instead, their afflictions were caused by radiophobia (an induced fear of radiation), aggravated by wrongheaded administrative decisions and, paradoxically, by increased medical attention which leads to diagnosis of subclinical changes that persistently hold patients’ attention.

The population exposed to some irradiation in the three main affected regions was estimated to be 98 million (out of a proximate population of nearly 250 million), and the number of post-accident recovery workers employed from 1986 through 1990 was 550,000. The latter received an added radiation dose of about 100 mSv. About 100,000 persons were evacuated from the most contaminated areas with a few weeks of the excursion, and they too received a total average dose of about 100 mSv. Small Chernobyl-originated doses (about 1 mSv/yr — less than global average natural background) were received by as many as 6 million residents of contaminated areas. The mortality for all causes of death among the emergency workers was actually lower than the whole Russian population,[7] and no increase in overall solid cancer or leukemia mortality has yet been detected.[8]

Bad administrative decisions made several million people believe that they were “victims of Chernobyl” although the average annual dose they received was only about one third of the average natural dose. This was the main factor responsible for the unnecessary economic losses, estimated to have reached $148 billion by 2000 for the Ukraine and to reach $235 billion by 2016 for Belarus.

Inconsequential Medical Effects of Chernobyl Fallout on the Population

In their year-2000 UNSCEAR[9] and a UN-organized Chernobyl Forum stated documents that, except for thyroid cancers in the population of highly contaminated areas, there was no increase in the incidence of solid tumors and leukemia, and no increase in genetic diseases. The latter conclusion should be contrasted with UNSCEAR’s unreserved 1958 conclusion quoted above that “even the smallest amounts of radiation are liable to cause deleterious genetic, and perhaps also somatic, effects.”

A small increase in registration of thyroid cancers in children under 15 years old had been noted in 1987, one year after the accident, in the Bryansk region of Russia, and the largest incidence, of 0.027% was found in 1994. Both of these studies were made too early to be in agreement with what we know about the slow growth of radiation-induced cancers: The mean latency period for both clinically manifested and “occult” malignant thyroid tumors in adults and children exposed to external and internal medical irradiation at these levels is about 30 years.

The registered number of 4800 new thyroid cancers between 1986 and 2002 among the children from Belarus, Russia and the Ukraine should be viewed with respect to the extremely high occurrence of dormant subclinical malignant tumors that contain transformed tumor cells and are quite common in the population. It appears that the increased registration of thyroid cancers in contaminated parts of these countries may be the result of a classical screening effect:

It is evident that medical screening on such a vast scale, probably the largest in the history of medicine, resulted in finding thousands of the “occult” cancers, expanded to forms detectable by modern diagnostic methods that were not in routine use in the Soviet Union before 1986.[5]

Data for the past 20 years show, in comparison to the Russian general population, a 15% to 30% lower mortality from solid tumors among the Russian Chernobyl emergency workers and a 5% lower average solid-tumor incidence among the population of the Bryansk district, the most contaminated in Russia. In the most exposed group of these people, a 17% decrease in the incidence of solid tumors of all kinds was found. In the Bryansk district, leukemia incidence is not higher than in the Russian general population.

Also, according to the most recent UNSCEAR report, no increase in birth defects, congenital malformations, stillbirth or premature births could be linked to radiation exposures caused by the Chernobyl fallout.

Because of this shortage of provable effects, the final conclusion of the latest UNSCEAR report was that the population of three main contaminated areas with high cesium-137 deposition density “need not live in fear of serious health consequences,” and forecast that “generally positive prospects for the future health of most individuals should prevail.”

Exaggerated View of Radiation-Induced Health Problems

Although publications of the Chernobyl Forum present a rather cautious overview of radiation-related health effects, there are three prominent inconsistencies:[4]

Inconsistency 1. Ignoring or downplaying the effect of screening for thyroid cancers of about 90% population, and interpreting the results with a LNT dose-response model.

Both the Chernobyl Forum and another international study ignore the aforementioned fundamental problem of occult thyroid cancers.

Standard mortality ratios for solid cancers among the Russian emergency workers indicate how cancer mortality of emergency workers differs from that in general population of Russia used as a control group. Between 1990 and 1999, the deficit of cancers among these workers ranged between 15% and 30%.

The incidence of thyroid occult cancers increased rapidly after the advent of new ultrasound imaging diagnostics. Reaching up to 35.6%, this incidence is more than 1300 times higher than the maximum 1994 thyroid cancer incidence found in Bryansk Region, Russia. This implies a vast potential for bias.

It seems that an epidemiological study on temporal changes of intensity of thyroid screening in the former Soviet Union was not performed. Instead, the overcautious LNT model was used to estimate thyroid cancers.

Inconsistency 2. Epidemiological studies that do not take into account amplified screening.

From among 134 persons who had been exposed to extremely high radiation doses, 31 died soon after the accident. Among the 103 survivors, 19 died before 2004. Most of these deaths were due to such disorders as lung gangrene, coronary heart disease, tuberculosis, liver cirrhosis, fat embolism and other conditions that can hardly be defined as caused by ionizing radiation. But the Chernobyl Forum presents them as a resulting from high irradiation and sums them up to a total of approximately 50 victims of acute irradiation.

After many summers, all the 103 survivors will eventually die. The Chernobyl Forum philosophy would then count them all, yielding a total of 134 victims of high irradiation. In fact, the mortality rate among these 103 survivors was 1.1% per year, i.e., less than average year-2000 mortality rate of 1.5% in the three affected countries.

Inconsistency 3. Projections of future fatalities caused by low-level Chernobyl radiation have been recently raised from an upper limit of 4000 up to exactly 9335.[10]

These numbers are not based on epidemiological data of cancer mortality observed during the past 20 years; epidemiology has demonstrated no such increase, but rather a decrease of solid tumor and leukemia deaths among exposed people.

Moreover, no requisite indication of statistical validity is given. In the absence of the reactor accident, 100-150 thousand eventual cancer-caused deaths would take place, out of 600,000 people under consideration. That normal incidence of cancer makes it difficult to sort out small incremental or decremental effects that might be due to Chernobyl’s radiation dispersion.

A realistic projection of future health for the millions of people that were officially labeled “victims of Chernobyl” should be based on actual epidemiological data, that is, data collected from clinical studies of exposed individuals.

However, the Chernobyl Forum chose instead to use the LNT radiation-risk model and performed a simplistic arithmetical exercise by multiplying small doses by a great number of people and inserted a radiation risk factor deduced from the Hiroshima/Nagasaki studies. However, people living in areas highly contaminated by the Chernobyl fallout were irradiated over a protracted time. The dose rates for the Hiroshima and Nagasaki explosions were a factor of about 100 billion greater than the average exposure rate of the “Chernobyl victims.”

Even WikiAnswers in 2010 carries the following question with the partly unjustified answer: How many people died in the Chernobyl disaster? Answer: “Only 30 people died due to the initial explosion. However, around 40,000 more have been expected to die.”  In point of fact, The evidence to date indicates that the eventual premature-death toll is so low as to be statistically indistinguishable from mortalities that would have occurred in the absence of the radiation fallout from the Chernobyl meltdown.

A Comprehensive Nuclear-Shipyard Worker Study-Report Sidelined by U.S. Government

In the course of dismantling irradiated components from decommissioned U.S. Navy nuclear reactors, a large number of workers at nine U.S. shipyards were exposed for many years to monitored low-dose occupational radiation — accumulated in excess of local environmental background.

Worldwide exposures to natural radiation sources are generally found to be in a wide range (see Table below). For the United States, it is 1.5 times higher on average, and 3 times higher at the nuclear-shipyard locations.

The naval-shipyard survey was screened by two independent technical-review panels. It was exemplified as “an ideal population in which to examine the risks of [ionizing] radiation in which confounding variables could be controlled.” Out of 600,000 non-nuclear shipyard workers, 32,510 age- and job-matched controls were selected to be compared to a cohort of 27,872 nuclear workers (from a pool of 100,000).

Experiment design, control, and analysis was formulated to avoid shortcomings in previous epidemiology of a population exposed to radiation. In particular, complete and documented dosimetry was obtained for all personnel during the entire study — an experiment-design protocol of major consequence for avoidance of systematic error.

This U.S. nuclear-shipyard radiation-worker study transcending the 1950s/60s through 1981 found clear evidence that it was not harmful to be exposed to a radiation dose comparable to natural-background.

The statistically significant results (95% probability) on mortality and cancer among the shipyard workers show that dependence on linear extrapolation (LNT) from doses much higher than natural background is not adequately supported by data collected for dose increments comparable to or less than natural background.

Epidemiological design for the U.S. naval shipyard worker evaluation carefully attended to the experiment structure and normalization of confounding factors. One glaring omission in the official U.S. government evaluations has been failure to mention the naval shipyard worker study at all, whereas it should be considered the “gold standard” in this category of radiation epidemiology.

A U.S. government-funded typewritten “Final Report” of the stringently controlled shipyard radiation-dose evaluation was completed in 1991.[11] However, the funding agency (Office of Health and Environmental Research, U.S. Department of Energy) failed to support traditional journal publication. Instead, in 2005, it was undertaken voluntarily by Ruth Sponsler and John Cameron.[12] The latter described it as the “world’s largest and most thorough study of health effects of low-dose-rate ionizing radiation to nuclear workers.” The Sponsler and Cameron review further validated the findings of innocuous effects from chronic low-doses of radiation.

The original shipyard study report also appears to have been a casualty of Cold War politics.

Unresolved Scientific Methodology for Understanding Radiation Effects

Advising against making LNT-based dose extrapolations have been several scientific and radiation-protection bodies, including the Health Physics Society, the French Academy of Science, and even the chairman of the International Commission on Radiological Protection.

Merely publishing unfounded numbers is harmful and amplifies Chernobyl fears. Any efforts to explain the intricacies of radiation risk assessments to the public or to compare these numbers with the much higher level of spontaneous cancer deaths have been futile exercises. The past twenty years proved that such efforts are worthless.

Making such calculations keeps a lot of people busy and it satisfies pre-conceived notions, but has no relation to reality and honesty.

The Chernobyl Forum’s intensive studies pale in the face of estimates by others which predict the incidence – without substantiation – of millions of Chernobyl-caused cancers and hundreds of thousands of deaths.

The actual upper limit is about 30 premature deaths – almost all caused by intense radiation and/or physical trauma. There is no substantive clinical evidence of Chernobyl-accelerated delayed-radiation casualties.

Sadly, academics and activists who originally expounded on worst-case fears have not publicly retracted their now-defunct hypotheses, nor their pretentious demands that have lead to unnecessary harm, expense, and fear.

Table: Significant Individual Radiation Dose Rates and Doses (from Jaworowski, 2010)


Dose Rates

 (milliSieverts per year)

Total Dose


Average Chernobyl fallout in contaminated regions of the former Soviet Union



Global annual natural exposure



Natural radiation in selected parts of the world

 >400 (Iran)

~700 (Brazil and southwestern France)


Average Chernobyl radiation received by inhabitants of the Northern Hemisphere



U.S. naval-shipyard workers exposure



Estimated average radiation in the Bryansk region of Russia 


World average global natural lifetime dose



Average annual whole body radiation for people living in the most contaminated areas of the former Soviet Union

 0.9 (Belarus)

 0.76 (Russia)

 1.4 (Ukraine)

Radiation dose from Chernobyl fallout in the United Sates in 1987                        



Global population Chernobyl dose in the next 70 years



U.S. naval-shipyard workers annual dose


Further details on some of these issues can be found in my Knol, “ETHICS IN SCIENCE: The Exaggeration of Radiation Hazards.”