Radiações lonizantes e Carcinogênese

• Autor(a) principal: Coelho, Aristides Pinto
• Data de Publicação: 2023
• Tipo de documento: Artigo
• Idioma: por
• Título da fonte: Revista Brasileira de Cancerologia (Online)
• Texto Completo: https://rbc.inca.gov.br/index.php/revista/article/view/4099
• topic: Radiação Ionizante; Carcinogênese; Efeitos da Radiação; Exposição à Radiação; Radiation, Ionizing; Carcinogenesis; Radiation Effects; Radiation Exposure; Radiación Ionizante; Carcinogénesis; Efectos de la Radiación; Exposición a la Radiación

The problems or radiocarcinogenesis are discussed on the basis of the known experimental facts, since the early physical events induced by ionizing radiations to the biological responses of molecules, cells, tissues, and organisms. The lethal dose (LD 50) for mice (Swiss albinos) with x rays were confirmed as 800 r after careful experimentation with Phillips X rays apparatus. This LD 50 was not altered when the mices were previously injected intraperitoneally with a phenolic derivate (trade mark NEOCITOL). Addmiting leukaemia as the main deleterious effects of human irradiation we discuss the factors related with leukaemia incidence. The litterature points out 24 cases of radioinduced leukaemia among Radiologists since 1911. Eighty one more cases are known as induced after clinicai irradiation (either with X rays or radioiodine and thorotrast) but the main source of radioinduced leukaemia are the japanese casualties after atomic explosions in Hlroshima and Nagasaki (116 registered cases). The atomic bomb explosions stimulated the studies of distribution of radioactivo isotopes in biosphere. The data we determined for Sr-90 in Brazilian biological materiais (vegetables, cow milk, human urine, and still born bones) shows that the artificial contamination in Brazil is about three times lower when compared to the contamination on the northern hemispheres countries (which is in accordance with the previsions). Brazil meanwhile has some regions with very high natural radioactivity and the table 7 shows these regions compared with similar zones in different countries with the highest leveis of natural radioactivity in the world. This data justifies our planification for an extensive Clinic-Radiobiologic study of several Brazilian zones which will enable better knowledge related to the biological effects on living beings (specially human beings) subjected, for a long time, to a relatively low levei of ionizing radiation. This program was started with a preliminary survey based on 65 leukaemic patients registered at the National Câncer Institute (Rio de Janeiro) during the period 1957/1961. Unfortunately the total number of registered patients is very low and do not have informations related with the length of time the patients lived in their birth place or elsewhere. So, we can not have final conclusions, yet. Therefore we should emphasize the higher incidence of registered patients originated from eastern regions with high levels of radioactivity. The figure 20 shows the geographic distribution, of the principal high radiation areas (marked as dotted lines) and of 65 patients on the Brazilian territory. The number in between parenthesis indicates the patients that are still living, or lived on their birth places. More complete inquiries, based on the hints proposed on this Work and sponsored by the National Câncer Service, are being distributed through all the Country and we hope that a wide Radiobiologic and Clinic study will contribute somehow to clear up the controversial problem.