It is impossible to estimate correctly the average effective dose of radionuclides after an emergency because the natural process of decay of short-lived radionuclides is very fast. The data for Chornobyl show that the level of ionizing radiation in contaminated areas may change more than ten thousand times in a year (see figure 10.5). After the Chornobyl and Fukushima accidents, attention was drawn to iodine-131, although in some places this radionuclide was not responsible for the main radiation exposure. Attention was also drawn to cesium-137, which in some cases was the source of people’s main radiation exposure several months after the accidents. At the same time, radionuclides such as barium-140, cesium-136, argentum-110m, cerium-141, ruthenium-103, strontium-89, zirconium-95, cerium-144, ruthenium-106, cesium-134, and strontium-90 were hardly less important, and in sum were probably more important than cesium-137 in forming the ionizing radiation background in the first few years after Chornobyl in some areas.
It is impossible to estimate true effective doses because dosimeters do not detect hot particles, which are micron-sized ceramic particles of melting nuclear fuel containing beta and alpha emitters. After Fukushima, they were observed on the West Coast of the United States. Most routine methods of radiation monitoring do not take into account these particles, but their effect on human radiation exposure can be significant.
It is impossible to estimate real effective doses because the effects of each radionuclide are not homogenous in space and time. The vertical migration of radionuclides into the soil causes the level of radiation in the atmosphere to decrease soon after radionuclides are released into an ecosystem. When radionuclides reach root zones (a depth of fifteen to thirty centimeters in the soil), plants bring the radionuclides back to the surface, thus increasing the level of atmosphere ionization for several years. Forest fires, strong winds, and migrating animals can cause horizontal migration, carrying radionuclides for hundreds of kilometers. There are regular daily and seasonal changes in the moisture and density of the top layer of the soil, as well as irregular changes related to precipitation and winds. Because of all of these factors, even at one fixed point, the radiation level may change greatly within hours, days, weeks, and months, making it very difficult—if not impossible—to make any correct calculations of the average external irradiation.
The concentration of radionuclides in different kinds of food varies greatly, as does the concentration of radionuclides even in the same foods. There could be variations in the concentrations of radionuclides due to the different ways of treating the same raw food, the coefficients of accumulation of different radionuclides, and differences in individual, seasonal, and local food preferences. Data from Chornobyl and Fukushima have a range of one to two orders of magnitude, which makes calculating an average meaningless. Calculating the average consumption of radionuclides through water and air is less prone to error than through food, but it is also imprecise because of variation in age, gender, body weight, and metabolism. All official dose calculations for the Belarusian people are based on anecdotal data on individual food consumption and behavior (time indoors and outdoors) for 1.1 percent of the irradiated population. It is, without question, nonrepresentative.
This depends on a person’s physical condition, age, gender, and diet. The average time for excretion of absorbed amounts of radionuclides used in official International Commission on Radiological Protection (ICRP) recommendations for calculating internal irradiation is so simplified that it is meaningless. For instance, according to the ICRP, the average biological half-life of cesium-137 is about seventy days, but in the case of four individuals, it was as varied as one hundred and twenty-four, sixty-one, fifty-four, and thirty-six days.
Official dose calculations were based on cesium-137, but in some places, americium-241, plutonium-238 and -240, and strontium-90, which are more difficult to detect, can be the main factors in overall internal and external irradiation.
Until recently, this “conditional person” was a phantom healthy white male, twenty years old and seventy kilograms in weight. The concept of this person is far from scientific and neglects consideration of individual differences as well as age, gender, and ethnic variations in radiosensitivity. Only since 2010 has the ICRP started recommending calculating doses separately for males and women (the male model is known as Golem, the female model Laura), yet they continue to neglect the full spectrum of individual variation.
In Chornobyl, as in Fukushima now, much of the data was falsified. In the Soviet Union, medical statistics were secret and were falsified for the first three and a half years after the catastrophe. The official medical data of the hundreds of thousands of liquidators, or cleanup workers, were altered by secret order of the Soviet Ministry of Public Health.
Instead of relying on individual effective equivalent dose, it is possible to rely on much more objective information on the impact of the radionuclide emissions after such nuclear catastrophes as Chornobyl and Fukushima by comparing:
• morbidity/mortality of populations with similar environmental and socioeconomic backgrounds, differing only in the radioactive contamination of their respective territories
• the health of groups of individuals studied year by year after the catastrophe;