Effect of Natural Ionizing Radiation on Health Indicators in Region with Monazite Sand in Brazil

<b>Objective</b> This article compares the occurrence of cancer and germinal damage in the city of Guarapari-Espírito Santo (ES), an area with high natural ionizing radiation, with other coastal cities. <b>Material and Methods</b> The evaluated cities were: Guarapari (ES), Campos (Rio de Janeiro), Rio Grande (Rio Grande do Sul), and Ilhéus (Bahia); the following factors were considered: mortality rate % from tumors (2007-2017), mortality rate % from tumors up to 15 years of age (2007-2017), hospital morbidity rate % from tumors up to 15 years of age (2008-2018), and hospital morbidity rate % from congenital malformation and chromosomal anomalies (2008-2018). Radiometric surveys were conducted by the Applied Physics Group at Universidade Federal do Espírito Santo. <b>Results</b> The natural radiation levels recorded in Guarapari resulted in accumulated dose between 3.65 and 10.95 mSv/year, and 1 mSv in the other cities. The highest average cancer mortality rates were: Rio Grande = 22.4%; Guarapari = 17.6%; Campos = 16.7%; and Ilhéus = 11.8%. The proportional hospital mortality and morbidity rates for cancer up to 15 years of age are as follows: Ilhéus = 3.36 and 5.87%; Rio Grande = 0.79 and 7.38%; Guarapari = 0.64 and 7.25%; and Campos = 0.39 and 9.13%. The hospital morbidity rate due to congenital malformations and chromosomal anomalies was 0.72% for Campos, 0.63% for Rio Grande, 0.62% for Guarapari, and 0.43% for Ilhéus. <b>Conclusion</b> There was no increase in cases of cancer or germ damage in Guarapari. These results indicated a dose threshold in the induction of these damages, contradicting the current linear no-threshold theory.