Abstract

Background: Naturally occurring radionuclides (NORM) present in phosphate-based fertilizers represent a potential environmental and occupational radiation concern due to their widespread agricultural use. Method: This study quantitatively evaluates the activity concentrations of 238U, 232Th, and 40K in fifteen commercial fertilizers sourced from the United States, Brazil, India, Egypt, and China using high-resolution HPGe gamma spectrometry. Radiochemical enrichment pathways, including acid digestion, solvent extraction, and ammonium diuranate precipitation, were numerically simulated to assess radionuclide concentration efficiency and practical feasibility. Results: Measured activities ranged from 12.8–88.6 Bq kg⁻¹ for 238U, 1.3–26.7 Bq kg⁻¹ for 232Th, and 11.6–2276 Bq kg⁻¹ for 40K, with NPK fertilizers exhibiting the highest potassium activity. Radium equivalent activity (Raeq) values varied between 15 and 175 Bq kg⁻¹, remaining below the UNSCEAR recommended limit of 370 Bq kg⁻¹. Occupational exposure modeling using RESRAD-BUILD and RESRAD-ONSITE estimated annual effective doses of 12–85 μSv y⁻¹ for fertilizer handling scenarios. Simulated extraction efficiencies ranged from 60% to 95% depending on the radionuclide and processing route, indicating limited practicality for regulated radioactive source production. A global awareness survey (n = 502) revealed low public recognition of fertilizer radioactivity. Implications: These findings demonstrate significant radionuclide variability across fertilizer types while confirming low radiological risk under normal use, underscoring the need for continued environmental monitoring and improved risk communication.