Natural radionuclide distribution in Brazilian foodstuffs and radiological dose assessment of coffee and fresh produce from southeastern Brazil

This study quantified the activity concentrations of 226Ra, 228Ra, 40K, and the anthropogenic 137Cs in coffee and fresh produce from southeastern Brazil and assessed the associated ingestion dose to consumers. Seventeen coffee samples and 27 fresh-produce items were collected from four municipalities representing distinct geological settings: Itatiaia and Rio de Janeiro (Rio de Janeiro state), and Poços de Caldas and Mariana (Minas Gerais state). Activity concentrations were determined by high-purity germanium (HPGe) gamma-ray spectrometry. Annual effective doses (E) and the Excess Lifetime Cancer Risk (ELCR) were calculated using consumption data from the Brazilian Household Budget Survey (IBGE) and dose coefficients from ICRP Publication 119. Coffee showed mean activity concentrations of 563 ± 26 Bq/kg (40K), 3.7 ± 0.6 Bq/kg (228Ra), and 1.4 ± 0.2 Bq/kg (226Ra), with a mean annual effective dose of 3.2E-02 mSv/year. Fresh produce exhibited marked regional variability, most notably for 228Ra: carrots from Itatiaia reached 27 ± 1.9 Bq/kg, nearly an order of magnitude above those from Poços de Caldas (3.3 ± 0.5 Bq/kg). 137Cs was below the detection limit in all samples, indicating negligible anthropogenic contamination. All individual annual effective doses represented a negligible fraction of the 1 mSv/year public dose criterion recommended by the ICRP. The highest individual values were observed for cassava from Mariana (1E-02 mSv/year), followed by papaya (Mariana) and orange (Itatiaia) at 9E-03 mSv/year each, and onion from Poços de Caldas (6E-03 mSv/year). Cumulative annual effective doses obtained by summing all analyzed fresh-produce items were 5.9E-02 mSv/year (Itatiaia), 2.2E-02 mSv/year (Poços de Caldas), and 6.3E-02 mSv/year (Mariana); combined with the mean coffee dose (3.2E-02 mSv/year), the total remained below 1.0E-01 mSv/year (<10% of the criterion). ELCR values for individual items ranged from 4E-07 to 4E-05. For reference, the global average ingestion dose from natural radionuclides is approximately 0.29 mSv/year (UNSCEAR, 2000).