The health situation
The nature of the biological effects which can be caused by ionizing radiation and a necessarily brief account of human health effects are outlined later in this brochure. That account is confined to direct physical effects. However, in the case of Chernobyl, as in many other radiological incidents, psychological effects have predominated.
The nature of these effects is complicated and it is wrong to dismiss them as irrational or to label them as "radiophobia". Many factors contribute to the development of this widespread public response. Among other things, there may be the historical association with nuclear bombs, or a lack of openness in the past on the part of governments, or the absence of intelligible explanations by scientists. It is noteworthy that some negative psychological responses were found in the populations of both "contaminated" and "uncontaminated" settlements studied by the project. Such effects are real and understandable, particularly in a mainly rural population whose work and recreation are closely interwoven with the land where restrictions may have had to be imposed by the authorities. Even physicians and others who might be looked to for guidance have often been confused. The result is that rumors multiply, fears increase, and any health problem is quickly attributed to a nuclear cause. Uncorroborated narratives may become commonly held wisdom and unverifiable statistical data may be accepted with insufficient scrutiny.
To address these problems, the international project set about reviewing the health situation reported by key medical centres and institutes in the Soviet Union. Subsequently, seven representative settlements of high contamination were selected for detailed independent health examination by the project medical teams. Six control settlements with the same socio-economic structure, but with insignificant contamination, were similarly examined.
Settlements Surveyed "Contaminated" ''Uncontaminated'' Bragin
The individuals to be examined were selected according to a statistical sampling scheme giving a representative distribution of age groups. As many as 250 people were examined in each settlement. The examination focused on disorders that had been reported or that might be expected. In addition to direct clinical examination, samples were taken and sent to the USA and Japan for laboratory analysis.
In any detailed clinical study of a particular population, some health disorders are bound to be detected due to the better documentation and closer scrutiny such a detailed study entails. This makes careful comparison with a similar population outside the contaminated area even more critical and rules out reference to pre-existing national or regional statistics.
Results of the health study
- There were significant non-radiation related health disorders in the population of both the contaminated and the non-contaminated settlements studied, but no health disorders that could be attributed directly to radiation.
- The accident had, and continues to have, considerable psychological consequences such as anxiety and uncertainty, which extended beyond the contaminated area. These consequences were compounded by the socio-economic and political changes in the USSR.
- The USSR data that were examined did not indicate a substantial increase in incidence of leukemia or cancer or hereditary effects. However, the data were not detailed enough to exclude a slight increase in the incidence of some tumor types. The adequately performed USSR studies, for their part, have not substantiated any of the reported health effects alleged to be due to radiation.
- Many of the clinical investigations by the USSR were done poorly, producing confusing or contradictory results. The reasons included inadequate equipment, lack of scientific information, and a shortage of well trained specialists. However, a number of USSR clinical studies were carefully and competently performed, and the international project was able to substantiate these studies in most cases.
- The children examined (mostly 2, 5 and 10 years old) were found to be generally healthy. The field studies indicated that a considerable number of adults in both the contaminated and the comparative settlements had substantial medical problems of a general nature.
- Diet appeared to be limited in range, but adequate. No significant differences in reported eating habits were found between the contaminated settlements studied and the uncontaminated. No detrimental effects on growth due to voluntary or official dietary restrictions imposed as a result of the accident were found. There was no evidence of differences in thyroid function between contaminated and comparison regions.
- The intake of iodine in the regions was found to be at the low end of the acceptable range. Most of the dietary components were found to be adequate. Vitamin intake, however, was not examined.
- Dietary intake of toxic elements (lead, cadmium, mercury) was low in comparison with those reported from many other countries and was well below the maximum tolerable intake levels specified by international organisations.
- Blood lead levels were found to be well within the normal range. Thus, no support was found for believing that the large quantity of lead dropped on the reactor to help control the accident had been widely dispersed in the atmosphere in vapor form and created a health hazard for the population at large.
- Review of USSR data indicated that reported cancer incidence had been rising for the last decade. The rise started before the Chernobyl accident occurred and has continued at the same rate since the accident. The project members could not judge whether the rise is due to improved detection and diagnosis or to other causes.
- The data did not show a marked increase in leukemia or thyroid tumors since the accident. However, owing to limitations in the statistical methods, the possibility of a slight increase in the incidence of these disorders cannot be excluded. Nor can the later development of increased numbers of cases after longer latent periods be excluded.
- There was no evidence from special eye examinations of radiation induced cataracts in the general population.
- High blood pressure was common among adults, but no differences were observed between the contaminated and the comparable settlements. Both resembled figures available for Moscow and Leningrad.
- Review of USSR data for settlements in the contaminated areas of concern, as well as for the three affected republics as a whole indicated relatively high infant and perinatal mortality levels. These levels existed before the accident and appeared to be decreasing.
- No statistically significant evidence was found of an increase in the incidence of foetal anomalies as a result of radiation exposure.
While the data were not detailed enough to exclude the possibility of an increase in some tumor types, it is emphasised that, on the basis of the doses estimated by the project and using internationally accepted risk estimates, future increases over the natural incidence of all cancers or hereditary effects would be difficult to discern, even with well designed long-term epidemiological studies. There remains a possibility of a statistically detectable increase in the incidence of thyroid tumors at a later date. Some general recommendations in the field of preventive medicine and for further investigations were also made by the project team.