Natural radioactivity in mineral phosphate fertilizers and its impacts on human health: an overview.

Humans are constantly exposed to radioactivity present in rocks, soils, and water, mainly from materials in the Earth's crust that contain chemical elements belonging to the radioactive series of uranium and thorium. An important anthropogenic source of these natural radioisotopes to the environment is fertilizers, widely used to increase agricultural productivity. Exposure to ionizing radiation can become a public health problem worldwide, since it is related to the development of different cancers in humans. The present study aimed to survey research on the radioactive content in different types of mineral phosphate fertilizers used around the world through a comprehensive review of the Scopus and Web of Science databases. About 80 scientific articles fit the purpose of this review. The concentration activity values found varied widely from one country to another, and there is no specific legislation that determines the maximum allowed limits of radioisotopes in these agricultural inputs. In addition, there are still uncertainties regarding the impact of natural radioactivity from fertilizers on human health, highlighting the need for further investigations on the subject.

Residential radon exposure and seasonal variation in the countryside of southeastern Brazil.

Poorly ventilated environments such as residences can accumulate radon gas to levels that are harmful to humans and thus produce a public health risk. To assess the risk from natural radiation due to indoor radon exposure, 222Rn measurements, using an alpha RAD7 detector, were conducted in Timóteo, Minas Gerais state, southeastern Brazil. Indoor radon concentrations, along with meteorological parameters, were measured every 2 h during both wet and dry seasons in 2017 and 2018. The mean concentration of indoor radon varied between 18.0 and 412.8 Bq m-3, which corresponded to an effective annual dose of 1.2 and 7.6 mSv y-1. Average radon concentrations were significantly higher during the winter dry season, and there was a strong positive correlation with humidity in both wet and dry season. Furthermore, concentrations showed an inverse correlation with atmospheric pressure, wind speed, air temperature, and solar radiation. The radon levels are generally above the limits recommended by international standards, meaning that mitigation measures are needed to improve air quality to reduce human exposure and risk. Finally, through the statistical analysis, it was possible to determine the differences and similarities between the sampling points concerning the geology of the place and the geographical location.