Committed effective dose by ingestion food grown in Pedra Branca State Park

Pedra Branca State Park (PEPB) is a Conservation Unit (UC) located in the municipality of Rio de Janeiro. Its geological formation is made up of a group of rocks with different lithologies, involving granitoids and gneisses. The presence of these rocks presupposes higher concentrations of natural radionuclides. As UCs conceptually do not allow agricultural practices, however, at the time of the park's creation, family farmers already living in the region, due to historical reasons, remained in that locality. In 2003, a group of farmers transitioned from conventional agriculture to organic farming following the creation of AGROPRATA (Rio da Prata Farmers' Association), an association of family farmers. Its members then began taking actions linked to environmental preservation. Organic farming encompasses an agricultural system with sustainable techniques that do not allow the use of chemical inputs (fertilizers, pesticides) either for fertility enhancement or pest control. The application of fertilizers can lead to increased doses of ionizing radiation in the population because fertilizers contain natural radionuclides from the uranium and thorium series, and studies show that the raw materials used in the production of phosphate fertilizers have high concentration of uranium. Radionuclides can be incorporated through ingestion and within the human body, they become a source of internal exposure. Therefore, identifying and quantifying the radionuclides present in food is an important step in environmental monitoring and radiological protection. From this perspective the activity concentrations of ⁴⁰K. ²²⁶Ra, ²²⁸Ra and ²²⁸Th were caculated in six samples of organic fruits and vegetables grown in PEPB, at sites belonging to the trails of Virgem Maria, Furnas, and Caboclos. Radionuclide analysis was conducted using gamma spectrometry with the use of a High Purity Germanium (HPGe) detector from Canberra, with a relative efficiency of 30%, in conjunction with the Genie 2000 software package. The activity concentrations of the radionuclides were calculated based on simulated detection efficiencies, and the effective dose from ingestion was estimated based on the annual food consumption from the most recent publication by the Brazilian Institute of Geography and Statistics (IBGE) and the dose coefficient from the International Commission on Radiological Protection (ICRP). (author)