Comparison of early forecasts of the incidence of thyroid cancer in residents of the Russian Federation after the Chernobyl accident with observational data

A review of methods for assessing doses in the thyroid gland, predictions of the long-term consequences of its irradiation and the actual incidence of thyroid cancer in residents of four regions of the Russian Federation with the most significant radioactive fallout after the Chernobyl accident are presented. The method for assessing doses in the thyroid gland is based on the results of monitoring in May-June 1986 of radioiodine in the environment, food and in the body of residents. Thyroid doses in the population were used to justify medical and social protection measures, as well as epidemiological studies. In addition, the authorities needed forecasts of the possible morbidity of the population in order to organize adequate medical care. Most of the thyroid cancer cases were predicted among the adult population, which was not confirmed by observations 35 years after the accident. The prognosis of the incidence of thyroid cancer in preschool children differed in different studies due to the use of different coefficients of reducing the biological effectiveness of 131I radiation in the thyroid gland and long-term external and internal irradiation of the whole body with a low dose rate compared to the effect of acute exposure. The increase in the incidence of thyroid cancer among children began five years after the accident at the Chernobyl nuclear power plant. Examples of the dynamics of the incidence for children in the Bryansk region of the Russian Federation are given. The 2018 UNSCEAR Report showed that for 1986-2015, among children and adolescents under 18 years of age on the day of the accident in Belarus, Ukraine and four regions of Russia, more than 19 thousand thyroid cancer cases were detected, of which the share of radiation-induced diseases was estimated at 25%. For four regions of Russia, this amounts to 460 cases with a range of possible estimates from 130 to 900 cases. The highest morbidity was manifested among younger children exposed at the age of 0-4 years. In older children and adolescents, the proportion of radiation-induced diseases has significantly decreased 30 years after the accident. In general, early forecasts of radiation-induced thyroid cancer incidence in children in four regions of the Russian Federation with high levels of radioactive fallout are consistent with the data of subsequent 30-year epidemiological observations within an order of magnitude. With regard to thyroid cancer in adults, such a comparison is difficult, since no radiogenic increase in the incidence has been detected.

Wildfires in the Atomic Age: Mitigating the Risk of Radioactive Smoke

This Perspective highlights the lingering consequences of nuclear disasters by examining the risks posed by wildfires that rerelease radioactive fallout originally deposited into the environment by accidents at nuclear power plants or testing of nuclear weapons. Such wildfires produce uncontainable, airborne, and hazardous smoke, which potentially carries radioactive material, thus becoming the specter of the original disaster. As wildfires occur more frequently with climate change and land use changes, nuclear wildfires present a pressing yet little discussed problem among wildfire management and fire scholars. The problem requires urgent attention due to the risks it poses to the health and wellbeing of wildland firefighters, land stewards, and smoke-impacted communities. This Perspective explains the problem, outlines future research directions, suggests potential solutions, and underlines the broader benefits of mitigating the risks.

Cancer Incidence of Finnish Sami in the Light of Exposure to Radioactive Fallout

This article summarizes the results of studies on the exposure of the Finnish Sami people to radioactive fallout and the estimations of the related cancer risk. We also discuss the lifestyle, genetic origin and diet of this population. The Sami people are an indigenous people who live in the northern part of Scandinavia and Finland. The review is based on the available scientific literature of Finnish Sami. The traditional Sami diet, high in animal products, persists in Sami groups still involved in reindeer-herding, but others have adopted the typical diet of western cultures. Studies have consistently shown an overall reduced cancer risk among the Finnish Sami people, except for stomach cancer among the Skolt Sami. Common cancers among the Finnish main population, such as prostate, breast and skin cancer are especially rare among the Finnish Sami. The incidence of cancer among the Finnish Sami are mostly similar to those of the Swedish and Norwegian Sami. To conclude, we observed no effect of radioactive pollution on cancer incidence. The lifestyles and environments of the Sami are changing, and their cancer mortality rate today is similar to that of the majority of the Finnish and western population.

Investigations of radiation exposures in the aftermath of the Chernobyl accident

Long-term assessment of the aftermath of the Chernobyl and Fukushima accidents deals with the study of radionuclide emissions and radiation exposure in heavily polluted regions. A signifcant difference in the composition and nature of radionuclide emissions during accidents at nuclear power plants is considered in the study - a largescale radioactive fallout transfer and precipitation over the USSR and Europe took place in Chernobyl due to the uncovered core of the reactor while at Fukushima a massive emission of inert gases occurred. It is noted that based on the density of precipitation, the data indicating that the vital doses of 137Cs remain signifcantly lower or within the range of natural radiation exposure were obtained. However, due to a short half-life (8.0 days) of 131I, there are no available comprehensive measurements of 131I exposure after the accident. It is noted that retrospective dosimetry of the effect of 131I on the thyroid gland through 129I with a half-life of 15.7 Ma allows to fll the gap in this issue. 137Cs precipitation was analyzed by gamma spectrometry, 129I was studied by accelerating mass spectrometry in soil samples from 60 places in zones II and III in the north of Ukraine and the thyroid gland radiation dose in the population. Critical comparing of the results obtained with those of rare direct measurements of 131I activity in the human thyroid gland reveal that the doses are at the lower limit. The actual radiation exposure in the contaminated regions of Northern Ukraine was considered by estimating the exposure dose in returnees in the village of Khrystynivka where 30 families live and consume locally produced products in the evacuated zone II, 75 km from the Chernobyl NPP. The results show that the additional irradiation with 137Cs the returnees received was low. The possibility of safe living in heavily polluted areas is noted. Under the normal way of life, the total radiation exposure of Khrystynivka village residents was within the natural radiation exposure range. Key words: radioactive fallout, radiation exposure, radiation pollution, irradiation of returnees.