Distribution of natural radionuclides, ingestion dose, and lifetime cancer risk assessment in cereals and cereal products from Nineveh Governorate, Iraq

Dietary intake of natural radionuclides represents one of the major pathways of internal radiation exposure, particularly in populations where cereal-based foods such as wheat and corn constitute staple components of the daily diet. Despite their nutritional importance, comprehensive radiological baseline data for cereal-based food products from Nineveh Governorate, Iraq, remain limited. In this study, activity concentrations of 226 Ra, 232 Th, and 40 K were measured in 25 cereal grains and cereal-derived food products using gamma-ray spectrometry with a 3″ × 3″ NaI(Tl) scintillation detector to evaluate ingestion dose and lifetime cancer risk. Higher radionuclide activities were observed in wheat bran and wholemeal products compared with refined foods, reflecting the influence of grain anatomy and industrial processing. Estimated annual ingestion doses ranged from 10.8 to 505.8 µSv·y − 1 for adults and 6.5 to 307.1 µSv·y − 1 for children (7–12 years), with 40 K identified as the dominant contributor to internal exposure. The estimated lifetime cancer risk associated with 226 Ra and 232 Th ranged from 0.05 to 12.82 × 10 − 4 for adults and 0.03 to 7.78 × 10 − 4 for children, with the highest values observed in wheat bran (S15). Monte Carlo uncertainty analysis ( N = 100,000) confirmed the robustness of deterministic dose estimates, yielding narrow 95% confidence intervals without significant tail behavior. Although some bran and whole-grain products exceeded conservative screening thresholds under lifetime exposure assumptions, the observed radionuclide levels remained within internationally reported ranges and do not indicate anomalous radiological contamination. These findings provide the first regional baseline dataset for cereal-based dietary radiological assessment in Nineveh Governorate and support future food safety monitoring programs.