The death toll from Chernobyl is often exaggerated, and the public perception of the incident is often far more grave than the reality. Here I try to summarize the effects and provide perspective on the scale of this tragedy. The root of the confusion comes from conflation of direct deaths with statistical deaths.

The direct death toll of Chernobyl was approximately 96: 1 died in the explosion, 30 from radiation poisoning and between 50 and 160 thyroid cancer deaths.

Statistical death means; individuals who have died prematurely, from cancer, as a result of acute or long-term radiation or pollution. In other words, the central estimate for the number of early deaths. Statistical death is a concept that could be liberally applied to all industrial disasters, but, is normally only applied to nuclear disasters.

The dominant model for modelling likelihood for death in the nuclear industry is the linear no threshold model, a.k.a. LNT model. LNT states that radiation is directly proportional to risk of death from cancer. Any amount of radiation is considered dangerous.

The true metric is actually years of life lost, as all we can do is calculate the central estimate of cancer incidences among the irradiated population. There is no way of ever knowing how many people died earlier than they would have. The common method is to calculate the probable number of cancer incidences and simply divide by 2. But this assumes they die exactly halfway through their lives. Whereas in the case of acute radiation poisoning, average radiation cancer going to occur halfway between the average age at which they are irradiated (median age of exposed population) and the average age of death (life expectancy) meaning that each radiation induced cancer results in closer to a quarter of a life lost, rather than half a life lost in an average aged population. But in the case of direct deaths, we don’t count years of lost life either; it is a death whether the person was 1 or 80 years old.

Direct Deaths

Cause of Death Count
Acute Radiation Syndrome 27
Cancer 1
Explosion trauma 1
Radiation Burns 2
Total 31

Statistical Deaths Estimate

We are confident that 50 to 160 thyroid cancer deaths occurred and approximately 5000 thyroid cancers occurred in total, primarily in children exposed to Iodine-131. Thyroid cancer has a survival rate of >99.8% if treated correctly and can be managed through medication throughout life. The survival rate of only 99%, meant that most of the thyroid cancer deaths were actually preventable had proper treatment been provided.

These deaths could also have been prevented had the victims taken Iodine replacement tablets within a few hours of the explosion. This would have saturated their thyroid with stable iodine, preventing uptake of radioactive Iodine.

Aside from thyroid dose: the average public whole body dose was well below 100mSv, the minimal dose at which there is experimental evidence for cancer according to the French Academy of Science.

Aside from these known deaths, we can predict an upper bound to the number of deaths from Chernobyl using the Linear No Threshold Model. 3 international organizations have done this and published their results:

Chernobyl Forum Legacy Booklet IAEA, 2003:

WHO 2006: Health Effects of the Chernobyl Accident and Special Health Care Programs

  • https://www.who.int/publications/i/item/9241594179 
  • Pg. 108: Theoretical upper bound estimate of 8250 deaths, using the LNT model with average doses 7mSv to 100mSv depending on population.
  • References Cardis et al., “Cancer consequences of the Chernobyl accident : 20 years on,” vol. 26, pp. 127–140, 2006. 

UN Report on Sources and Effects of Ionizing radiation Volume II, Annex D, 2008

So let us directly address the question of what happened to the 200,000 liquidators with an average dose of approximately 100mSV, and the 126 ARS survivors who all survived a dose >800mGy. A more accurate cancer incidence model than the linear no threshold model, that accurately reflects the state of medical science, for low radiation dose is the sigmoid no threshold model. A version of it was proposed in Jack Devanney’s ‘Why Nuclear Power was a Flop’.

Unfortunately, we only have dose data in the first year (when almost all dose was sustained) for the 67,500 Russian liquidators, not the Ukrainian, Belorussian or others. Central Estimate of Premature Deaths assuming SNT using the Stratified Dose Estimates for Russian Liquidators:

  • Russian Liquidators (67,500): 213 deaths
  • Crudely Extrapolating to the (200,000) Total Liquidators: 631 deaths.

The total lost life expectancy (LLE) is almost entirely in the liquidator population of 200,000. Assuming an average age of irradiation of 25, and life expectancy of 75, with a mean death age of 50 an average third of each life is lost i.e. 210 full lives. This equates to a lost life expectancy to an individual within this 200,000 strong group of 29 days. This contrasts parallels the LLE associated with coal pollution: around 23 days for the average American.

Accuracy of Liquidator Doses

The level of occupational monitoring was very poor by modern standards, and wearing of personal dosimeters was allegedly banned in Medvedev’s account. First-hand reports from the worst exposed, known as ‘Bio-Robots’ assert that they were recorded with far lower doses than the actual conditions on the reactor building roof.

This is attested in:

  • G. Medvedev, Chernobyl Notebook. Moscow: Novy Mir, 1989 and;
  • Z. A. Medvedev, The Legacy of Chernobyl. Oxford: Basil Blackwell, 1990.

I think it is worth confronting how the dose estimates for the exemplar group of Russian liquidators were actually arrived at in Kashcheev 2015 because most people will correctly suggest that the Soviets had a incentive to lie about this and a track record of doing so about such things. Kashcheev 2015 gets its data from Pitkevitch et al. 1997. This data is from the Russian National Medical and Dosimetric Registry (RNMDR). It is based on the documents given to liquidators by the over 600 organizations that performed dosimetry monitoring in the zones of operation. It covers 119 416 Russian liquidators (78.4% of the total number of the 152 325 Russian liquidators).

Pitkevitch et al. performed a plausibility analysis using “different statistical characteristics were derived to assess the reliability of the information.” In short, they compared the known dose rates in ‘recovery operation’ locations against where they are recorded to have lived during their time at Chernobyl and for what duration.

It notes that:

  • plenty of liquidators recorded doses which exceeded the official limits, implying a reliability in the data as, if the data were fabricated or moderated, officials would have redacted such data.

It says…

“The distribution of absorbed doses of the liquidators in different calendar years is consistent with the radiation situation in the zones of radiation contamination and with the type of work carried out by the liquidators”.

And…

“Information of the RNMDR is, as a statistical aggregate, generally consistent with the data on the radiation situation in the RO zones”.

It states: “In conclusion, the statistical analysis of the doses registered for liquidators in the RNMDR does not bring out major evidence of unreliability.”

But in general, the data is seriously lacking because it doesn’t have any information of individual ‘routes’ and duration for liquidators in the zone of radioactive contamination during the course of their work. However, the sheer volume of data does imply reliability as a data fabrication exercise on this scale, would be quite clearly visible in the data. Even when teachers self-report their student’s grades, basic statistical methods are able to determine whether it contains statistically implausible data.