Chernobyl Liquidators' Health
as a Psycho-Social Trauma
How — and if — Chernobyl data
can be used to assess impact
of radiation on health?
Insider's point of view
(The paper delivered at the European Parliament
at the Workshop on discussion of the project
of the European Union radiation protection standards
(8 February 1998, Brussels))
The paper discusses reliability of Chernobyl data on doses and health effects and their applicability for setting radiation protection standards. It states that Chernobyl officially registered doses are inappropriate to the purpose. Extraction of more adequate information about condition of irradiation in Chernobyl seems to be achievable by (1) complementing medical-epidemiological studies with additional historic-archival research and (2) distinguishing different professional, social and temporal groups of affected in the studies. Another recommendation consists in studying a wider range of diseases as possible consequences of Chernobyl irradiation.
Setting of radiation protection standards both for professionals and the general public inevitably — directly or indirectly — involves a relationship “irradiation dose — health response in the population”. The dose-response relationship describes a proportion/number of individuals in the population exhibiting a specific health effect from a defined exposure (dose) to the hazardous factor (radiation).
Accuracy of recording both the dose and health response data is of crucial importance especially for extrapolations at a low dose range in which permissible limits of irradiation are actually set. The requirement of accuracy for the health response means that its monitoring is, on the one hand, broad enough to cover all possible health effects, and, on the other hand, rigorous enough to ensure that radiation is the exact cause of the effects observed.
Based on both the author's personal experience in Chernobyl in 1986 and the further studies of Chernobyl consequences, the purpose of this paper is:
1) to assess the reliability of Chernobyl dose-response data and the possibility of their application for setting radiation protection standards;
2) to suggest more adequate ways to interpret the data available.
In the summer of 1986 the author of this paper served as a commander of a radiation surveillance platoon in Chernobyl. Along with the monitoring of the radiation situation in different parts of the affected area and the management of this monitoring, the author was responsible for the documentation of this work including registration of irradiation doses.
The scope of this paper is limited mostly to Chernobyl liquidators who served in the military troops. The military liquidators were mostly civilians drafted from the reserve to work in Chernobyl. They constitute, probably, the largest portion of the liquidators (at least in 1986—1987) with estimated numbers varying from 600 000 to 900 000.
Some approaches suggested may be of use for the study of non-military liquidators and other affected groups (both those evacuated and inhabitants of the contaminated areas).
1. Chernobyl Doses
— Should the Chernobyl documented doses be taken into consideration in assessing the effects of irradiation on the basis of the dose-response relationship? Yes or No?
— No. Rather not.
Chernobyl documented doses are notorious for their inaccuracy because of (1) the poor methods for measuring personal irradiation doses and (2) deficiencies of the system of their registration in Chernobyl.
As an almost absolute rule, no personal irradiation dosimeters were used for this purpose (at least in 1986, in military troops). In the first days of the Disaster, electrostatic (condenser) personal dosimeters, which had been expected to be used both for military and for civil defence purposes, proved to be inefficient and were discarded. The personal dosimeters of other types were simply not available or, if available, were only in limited quantities. These were (with a few exceptions) inaccurate or inefficient in practice for a set of different reasons. In this situation, to control irradiation doses of the personnel, an official decision was adopted to consider only the doses obtained by multiplication of a measured level of radiation (Roentgens/hour) at the site the person worked by the actual working time (hours). An official representative, who was responsible for performing the work at the given site, signed the document confirming a receipt of the dose by a person or a team. This “primary” document was delivered to the military regiment headquarters, where the dose was entered into the register of the irradiation doses of the regiment's personnel. The “primary” documents were destroyed within several days after their receipt.
The described registration scheme distorts the documented doses both for technical (inaccuracy of the measurements, especially at sites with varying level of radiation) and social (corruption) reasons. No standard procedure to assess the accuracy, a range within which the true value of the physical dose may occur with a given probability, can be suggested. Thus, by no means the Chernobyl documented doses should be regarded as quantitative data.
Neglecting this very important, principal point can lead to a variety of mis-conclusions, mis-recommendations and, finally, mis-standards.
However, within this basic (necessarily sad) framework, a more adequate understanding of the degree and the conditions of the irradiation of liquidators seems to be achievable. For this purpose the irradiated liquidators are to be studied only within certain groups uniform as for the following parameters:
— temporal: a period of the Disaster in which the person worked in Chernobyl;
— social: social status of the person during the work in Chernobyl;
— professional: type of the work done in Chernobyl;
— some relevant features of post-Chernobyl medical treatment.
The above list is based on the following considerations:
1. Possible deviations of real and documented doses can be essentially different in different periods and for different professional and social groups:
— temporal factor: reliability of documented doses in general increases with the time passed from the explosion (the doses of 1987 can be considered as more reliable than those of 1986, and in 1986 the data from autumn seem more accurate than from summer). This is a result of: (1) better management of the dose control and (2) smaller and more uniformly distributed levels of radiation;
— professional factor: the documented doses are in general closer to the real doses for work performed at smaller working sites with a constant level of radiation (e.g., for clean-up works at the NPP starting approximately from the summer of 1986). For radiation surveillance work and for the decontamination “wash-up” treatment (for the vehicles leaving the zone) correspondence between the documented and the real doses cannot be established;
— social factor: liquidators from groups with higher social status had more possibilities to influence their documented dose both at the stage of receipt of the “primary” dose document at the work site and at register-keeping. For liquidators-senior officers, as a first approximation, overstatement of the documented doses should be expected. Motives to overstate the documented dose were reduction of the term of service in Chernobyl, remuneration, social compensations and different privileges for irradiation dose, equal or exceeding the total maximum permissible dose of 25 Roentgen and so on. (Though some of the senior officers and highly qualified specialists understate it to protract a stay in Chernobyl because of professional or career interests). For the group with low social status (soldiers, to some extent junior officers) — understatement of the documented dose should be expected (as a realisation of the state policy at that time).
Let's illustrate the importance of the social factor by the following example:
Assume that a “true dose X — health response Y” relationship for a sample of the affected has 1 maximum. Then, imagine that the true values of X is unknown, and a half of the sample under survey has documented doses underestimated for 25% as compared to their true values, and the other half — overestimated for 25%. In this case of distortion of the doses, we will obtain splitting of the original single maximum into 2 symmetric maximums; a distance between them will be equal to half of the value of a true X of the original maximum. Within this simple model we can have asymmetric maximums for different ratios of “under-” and “overestimated” fractions.
Similar pictures are characteristic for many Chernobyl-induced health responses (and, moreover, for irradiation effects on many biological and chemical systems). However, the above example shows that they (unlike the ones for biological and chemical systems) can be explained as well in social terms, suggesting that the social factor should be taken into consideration when interpreting them.
It would be quite useful to examine dose-response relationships for populations of soldiers and generals separately. It is also worth noting that military liquidators, because their social status is more strictly segmented by military rank, provide an excellent basis for such a socio-medical study.
2. By no means can Chernobyl irradiation be considered as purely external. In the different periods of the Disaster, the amount of radionuclides incorporated in the organism varies dramatically. This occurs because (1) composition and concentration of the radionuclides in the environment were essentially different and (2) there were different conditions of life and work.
On basis of the radiation situation, as a first approximation, one can distinguish the following periods for the first two years of the Disaster:
— initial stage: 26 April 1986 — first days of May;
— May 1986 (until cease of intensive radiation leaks from the exploded unit 4);
— summer-autumn 1986 (until completion of the Sarcophagus over the unit);
— winter 1986/1987 and 1987 (radiation levels decreased essentially).
Every previous stage represents a noticeably higher level of radionuclides' intake as compared to the following one. Within each period, different professional groups of liquidators had essentially different probability to intake radionuclides with the air, dust and water droplets.
Then, the degree of the internal irradiation of a person varies considerably depending on whether (and when) the person was treated after Chernobyl with medicine eliminating radionuclides from his/her system. For example, in 1986—1987 (that is when it was the most needed) the treatment with a very effective Soviet medicine “Enterogel” was available only to persons with high social status — not for laymen.
2. Chernobyl Health Effects
Within the particular scope of this workshop, several practical aspects of this very controversial and very painful issue need to be highlighted.
To accept radiation protection standards a decision-maker should be certain and confident that the decision accepted is based on data embracing ALL health consequences of irradiation.
Unfortunately, this does not seem to be the case for Chernobyl data. Main research in the field has concentrated on certain domains and led to either well-established facts (e.g., increase of children's thyroid gland cancer at the contaminated territories; several hundred deaths from acute irradiation disease) or very hot disputes (e.g., about an increase of various cancers caused by Chernobyl).
However, the experience of irradiated liquidators gives some grounds to consider that radiation — in doses not sufficient to produce direct irradiation damage — acts as an additional harmful factor of the environment and leads to general aggravation of the individual's and population's health. Of course, it is quite difficult for modern epidemiology to trace and attribute increases of such diseases to Chernobyl irradiation in the highly stressful post-USSR societies.
On the other hand, there definitely are possibilities not investigated by epidemiology yet. The list of diseases and of the health effects caused by irradiation and considered in assessment of its impacts definitely needs expansion.
One example is the irradiation reaction of blood. This disorder of the blood count occurs several months after the exposure (when the blood cells produced under irradiation mature). Usually it is not regarded as important because the changes are reversible. Nevertheless it is a disease and does quite observable (though, fortunately, temporal) damage to the health. It provides researchers with an important opportunity to study the impact of low doses because: it is definitely caused by irradiation, it is well-documented, and it affected a large number of people (at least several hundred thousand liquidators).
Another remark concerns interpretation of statements of epidemiology into statements of law. The matter is that epidemiology and law have different (sometimes even opposite) “presumptions of innocence”, “precautionary principles” (default assumptions, in short).
Namely, as a science, of which one of the worst sins is considered a wrong causation, epidemiology advocates a suspected cause of the disease until it will be proved “beyond reasonable doubt”, by means of all the epidemiological techniques available, that exactly this reason causes the consequences observed. However, the available techniques can be not sufficient enough to provide the proof required.
It means, a rather typical statement “Epidemiology has no evidence that increase of disease Y is connected with radiation (or any other cause X)”, if expressed explicitly, actually means “Epidemiology has no adequate technique for making conclusions about whether an increase of disease Y is caused by radiation (X) or not”.
That makes some difference, doesn't it?
Unfortunately, the understanding of this important fact usually escapes not only the general public but also the decision-makers and mass-media.
At the moment the whole range of medical consequences of Chernobyl irradiation remains unclear: (1) because they are not developed yet, (2) because they are hard to assess owing to their connection with social, economical and other issues, (3) because of lack of adequate technique for their study, and, finally, (4) because of a lack of general understanding of the Chernobyl phenomenon peculiarities.
And, in order to extract the information necessary for the proper handling of radiation, studies of the Chernobyl experience should combine features of medical-epidemiological surveys with those of historical and archival research. Different professional, social and temporal groups of the affected should be studied separately. More diseases should be taken into consideration as possible consequences of irradiation, including not radiation-specific, “common” diseases. Some new means to epidemiologically assess consequences of irradiation of population should be searched for.
Design by: M.Opalev
Studio ARWIS Kharkov, 2001