The Chernobyl nuclear power plant accident happened on April 26, 1986. We investigated the cause of the striking increase in frequency of thyroid cancer in children who lived within a 150 km radius of Chernobyl and who were born before and after the accident. No thyroid cancer was seen in 9472 children born in 1987-89, whereas one and 31 thyroid cancers were recorded in 2409 children born April 27, 1986, to Dec 31, 1986, and 9720 born Jan 1, 1983, to April 26, 1986, respectively. Short-lived radioactive fallout caused by the Chernobyl accident probably induced thyroid cancer in children living near Chernobyl.
Health effects as a result of the accident at the Chernobyl nuclear power plant occurred in 1986 are considered in the paper. Wrong prognosis of the health effects with respect to mortality and morbidity among the population exposed to low radiation doses is shown. Proven increase in thyroid cancer cases among people who were children aged from 0 to 18 at the time of the accident is shown. Linear relationship between thyroid cancer cases and dose to thyroid ranged from 0.2 to 4.0 Gy is considered. An additional absolute risk of thyroid cancer in children varies in the range 1.9-2.6 cases per 10(4) person-year Gy. During the fifteen years following the accident no cases of acute and chronic radiation sickness have been revealed because the population living in contaminated areas received low radiation doses. Also, exposures to low radiation doses did not result in excess of malignant tumors among population. In some cases the outcomes of acute radiation sickness were as follows: radiation damages to the skin, cancer cataracts, development of oncopathology.
Presented are the results of morphological studies of radiation sickness, congenital malformations and malignant tumors which have developed in Chemobyl victims. Until now consequences of the accident remain a subject of practical and research medicine. Scope of relevant topical problems the pathologists will have to investigate in the future is discussed.
The magnetic fields from overhead power lines and other electromagnetic sources were determined at the birth and diagnosis dwellings of all tumor cases reported in the county of Stockholm during the years 1958-73 for individuals 0-18 years of age. The study was limited to 716 cases having a permanent address in the county both at time of birth and diagnosis. An equivalent number of controls was matched to the cases according to church district of birth, age, and sex. Outside each dwelling, the occurrence of visible electrical constructions (6-200-kV high-voltage wires, substations, transformers, electric railroads, and subways) within 150 m of the dwelling was noted. Also, the 50-Hz magnetic field was measured outside the main entrance of the dwelling. Visible 200-kv wires were noted at 45 of 2,098 dwellings and were found twice as frequently among cases as among controls (P less than .05). The magnetic field measured at the dwelling varied between 0.0004 to 1.9 microT (mean value 0.069 microT). The magnetic field was higher (0.22 microT) at dwellings with visible 200-kV wires than at those without such wires. Magnetic fields of 0.3 microT or more were measured at 48 dwellings, and were found twice as frequently among cases as among controls (P less than .05). The difference was most pronounced for dwellings of nervous system tumors and was less for leukemias.
The Chernobyl accident resulted in a number of cases of thyroid cancer in females under the age of 20 y. Many of these individuals were treated with surgical removal of the thyroid gland followed by 131I ablation of residual thyroid tissue. Epidemiologic evidence demonstrates that 131I treatment for thyroid cancer or hyperthyroidism in adult women confers negligible risk of breast cancer. However, comparable data for younger women do not exist. Studies of external radiation exposure indicate that, for radiation exposures of as low as 0.2-0.7 Gy, the risk of breast cancer is greater for infant and adolescent female breast tissues than for adult female breast tissues. METHODS: The effective half-time of 131I measured in athyrotic patients was used together with the OLINDA/EXM computer code to estimate doses to breast tissue in 10-y-old, 15-y-old, and young adult females from ablation treatment. RESULTS: The dose to pediatric and young adult female breast tissue associated with a 5.6-GBq (150 mCi) ablation treatment may range from 0.35 to 0.55 Gy, resulting in a lifetime risk of breast cancer ranging from 2-4 cases per 100 such individuals exposed and a lifetime risk of solid tumors ranging from 8 to 17 solid tumors per 100 such individuals exposed. Administration of multiple ablation treatments, as often occurs with metastases, could result in doses ranging from 0.7 to 1 Gy, with corresponding increases in the lifetime cancer risk. CONCLUSION: These estimates suggest the need for additional research and a possible need for surveillance of young Chernobyl thyroid cancer patients who received 131I ablation treatment.
Beginning approximately 4 years after the Chernobyl nuclear accident a steady increase in the incidence of thyroid cancer was observed in children and adolescents of the Bryansk Oblast, which received the highest level of radionuclide contaminants in Russia. We examined the spatial relationship between the residence location of patients with identified thyroid cancer (0-18 years old at the time of the accident) and a number of geographic parameters to better account for the etiology of thyroid cancer spatial distribution. Geographic parameters analyzed included spatial distribution of 137Cs and 131I in soil, population demographics, measurements and reconstructions. of absorbed thyroid 131I doses in the population, and maps of major transportation arteries. An interesting finding is the lack of a consistent correlation between the spatial distribution of radionuclides in the soil and thyroid cancer incidence. Instead, most of the thyroid cancer cases were diagnosed in settlements situated on major railways and roads. Correlating population with thyroid cancer cases and transportation arteries reveals a much higher cancer rate on or near major roads and railways than at a distance from them, again independent of radionuclide soil concentration. There are other important factors, of course, that must be considered in future evaluations of this phenomenon. These include the influence of iodine endemic zones, genetic predisposition to thyroid cancer, and duration of residence time in contaminated areas. The feasibility of radionuclide transport on railways and roads is discussed, together with the vectors for transfer of the contaminants to the human population. Developing a model to reconstruct the radiation dose to the thyroid over time in this geographic region is proposed in light of the impact of transportation arteries. Specific studies are outlined to provide the data necessary to develop this model as well as to better characterize the feasibility and scientific validity of the contribution to human health effects of this transport factor. Transport factor refers to the transport of radionuclides on transportation arteries and the transfer of these agents to the human population residing in the vicinity of these arteries. If the impact on thyroid cancer of the transport of radionuclides on major railways and roads is indeed significant, a major reappraisal of the risk of large-scale radioactive release into the environment is necessary.
It will be clear from the aforegoing that occupational standards have varied over the past 30-40 years since the beginnings of the nuclear industry. Our perception of risk rates for cancer mortality and genetic effects has changed, such that the rates have been constantly revised upwards. Logically, dose limits should have been reduced in proportion, but this assumes a constant approach to the "tolerability" or "acceptability" of risk and this has not been demonstrated. Dose limits are not seen by management in the nuclear industry as the only plank in the structure of radiation protection; emphasis is also being given to the "optimization" ethic. In these circumstances a good test of the efficacy of the system of radiation control in limiting health effects is needed. As can be seen, no such study is available and, given the doses received and the numbers of workers involved, it is unlikely that any epidemiologic study, apart from studies on miners, will have sufficient statistical power to be totally unequivocal. However, some studies have shown cancer mortality associations with radiation exposure that are significant. Probably the best way to mitigate the inherent drawbacks in these studies is to pool data-sets, and this is being done. Other improvements will include estimates of cancer incidence in countries with cancer registries (e.g., U.K., Canada, and Sweden) and to perhaps go beyond epidemiologic data to consider sensitive biologic markers as indices of exposure. Overall the conclusion must be that the radiation industry cannot be complacent and for some tasks in the processes involved (e.g., uranium mining) there is strong evidence of a history of unacceptable health effects occurring.