The investigation of spices by use of instrumental neutron activation analysis

The spices consumed in the U.S. diet contain many elements other than the pure spice that many assume they eat. In particular, most of these spices contain radionuclides that are absorbed from the ground soil and water that contains trace contaminants. For this research, instrumental neutron-activation analysis (INAA) was used to determine the activities of U-235 fission products in common spices. Using this information, the concentrations of natural uranium in these spices and the doses to individuals consuming the spices were calculated. Nine spices and two standard reference materials were selected for analysis. The spices chosen were cinnamon, cumin, turmeric, oregano, thyme, cayenne, ginger, chili powder, and paprika. For comparison, NIST-certified "orchard leaves" and "spinach leaves" were used. The spices and standards were placed in polyethylene vials and heat-sealed. The samples were divided into irradiation groups of 30 seconds, 12 hours, and long irradiations of 10 to 12.8 hours. After irradiation, all samples were counted on an HPGe detector for time periods ranging between 10 minutes to 65 hours. After counting, the results were analyzed using Genie 2000 software. The Genie 2000 analysis revealed no detectable fission products for samples irradiated for 30 seconds or counted for short times. However, long counts revealed the high-yield U-235 fission products molybdenum-99 and what appeared to be cerium-144. However, after comparing the experimental values with the calculated values, it was determined that the experimental values of Ce-144 were not credible and the focus shifted solely toward Mo-99. From Mo-99 activities, uranium content could be calculated. Using this information, the committed dose equivalent (CDE) and the committed effective dose equivalent (CEDE) for ingestion of uranium was calculated. The CEDE values were based on an assumed ingestion of 6.5 grams of each spice per year. The doses from ingesting these spices ranged from CDE and CEDE doses of 4.31E-05 mSv and 3.08E-06 mSv, respectively. Based on these measurements consumption of these spices, even when combined, would not result in annual CDE or CEDE doses approaching the limits for the public of 50 mSv and 1 mSv, respectively, for a year of chronic ingestion.