Avaliação da radiação ionizante como fator de risco para a incidência de câncer de mama em Goiânia

• Main Author: Lage, Leonardo Bastos
• Publication Date: 2016
• Format: Master thesis
• Language: por
• Source: Repositório Institucional da UFG
• Download full: http://repositorio.bc.ufg.br/tede/handle/tede/6104
• topic: Câncer de mama; Fator de risco; Radiação ionizante; Monitoramento ambiental; Proteção radiológica; Saúde pública; Breast cancer; Risk factors; Ionizing radiation; Environment monitoring; Radiation protection; Public health; CIENCIAS DA SAUDE

Ionizing radiation has been cited as one of the risk factors for the increasing incidence of breast cancer, as demonstrated in studies after nuclear explosions. In the end of 1987 the world’s largest radiological accident in urban areas occurred in Goiânia, which brought concern about the possibility of increasing the rates of cancer incidence induced by radiation. This research aims to evaluate whether exposure to ionizing radiation to which women are subjected can be associated with the incidence of breast cancer in Goiânia. The defined study area is the central region of Goiânia, or the Sanitary Districts of Campinas-Centro and Sul, in which are the seven major accident sources of contamination with Cesium 137, and also, as shown by previous study, the majority of new cases of breast cancer (60,43 %). We used the geographical division of the city in census tracts and health districts. The data collection was divided in two stages: the first, for the survey of radiometric measurements, and the second, for identifying the addresses of women diagnosed with breast cancer. The radiometric survey occurred between 2010 and 2014, in which was used an environmental gamma radiation mobile measuring system. This system was composed by a high-sensitivity detector coupled to a Global Positioning System (GPS) and a microcomputer. The assembly was installed on a motor vehicle so that the height of the detector is found at one meter from the ground, and programmed to obtain a measurement of the doses absorbed in the air rate each second. The data collected were: doses absorbed in the air rate, geographical coordinates, altitude, date and time of acquisition. From Mobisys software, files were generated and from ArcGIS 10.0 platform, geospatial assessment survey through the elaboration of thematic maps and geospatial analysis statistics. The annual averages of effective doses and collective effective doses were estimated from the rate of doses absorbed in air collected by the system and the resident population in the census tracts. The second stage begun from the data collection at the Registry of Goiânia’s Population Based Cancer (RCBPGO), in which were identified addresses of women diagnosed with breast cancer between 2001 and 2010. Part of the data was geographically referenced and using census data were estimated and compared the annual averages of crude rates of incidence. The spatial correlation of groups (clusters) of new cases has been verified, through the Moran index, and from geographically referenced radiometric measurements obtained in the previous step, the correlation between the incidence of breast cancer and ionizing radiation levels was assessed by unconditional linear regression. The results were presented in two papers. In the first, radiometric surveys were conducted in 1.405 of the 1.636 (85,9%) census tracts sectors that make up the seven Sanitary Districts in the city of Goiânia. In total 197.811 geographically referenced measures of the absorbed dose rate in the air were made, with a average of 29,85 ± 7,47 and amplitude from 9,17 to 629,88 nGy/h. From these values were estimated the average of annual effective dose and collective effective dose for outdoor environments, with values of 0,036 ± 0,003 mSv/year and 28,51 ± 11,68 man.mSv/year, respectively. The levels of exposure to external gamma radiation, found in the city of Goiânia 28 years after the radiological accident with Cesium- 137, are compatible with the values estimated by UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation). And the value of the annual average of effective dose in Goiânia, is lower than in other places in Brazil, which have only "background" of natural radiation outdoors. The results obtained in this study indicate that the dosimetric situation in Goiânia does not present undue risk to people and the environment. In the second article, were identified 4.105 new cases of breast cancer, 2.233 in the study area and 1.286 (57,59%) of these geographically referenced. The annual average values of crude rates of incidence, considering the total numbers of cases and geographically referenced presented in the study area are, respectively, 102,91 and 71,86 new cases per 100.000 women. The crude rate of incidence in Goiânia was 66,59 cases per 100.000, while in the study area was 102,91 cases per 100.000 and, outside the area, 46,86 cases per 100.000. These values are within the range of average values presented by other Brazilian capitals, which is 130,99 cases per 100.000 in Porto Alegre-RS, and 20,04 cases in Macapá-AP, and the national average in the capital of 79,37 cases per 100.000 women. The cluster analysis showed a slight spatial correlation of crude rates of breast cancer incidence in three small sets of census tracts, far from the accident sources of contamination with Cesium-137. The scatter plot points and the R² value didn’t indicate any association between the crude rates of incidence and radiometric measurements. This study supports the hypothesis that ionizing radiation levels to which women living in Goiânia are exposed, are not associated with the emergence of new cases of breast cancer.