Background <p>Radioactive heavy metals, including uranium, strontium-90, caesium-137, radium, thorium, and plutonium, pose potential health risks to nursing infants through breast milk transfer. Understanding the extent of contamination, transfer mechanisms, and health implications is critical for public health policy.</p> Objective <p>This scoping review synthesises evidence on radioactive heavy metal contamination in breast milk, maternal-infant transfer mechanisms, and associated health impacts on early life development.</p> Methods <p>A comprehensive scoping literature search was conducted in December 2024 across multiple electronic databases. After deduplication, 161 unique papers remained. An AI-assisted relevance scoring approach (SciSpace biomedical agent) was used to prioritize screening; final eligibility decisions and data extraction were performed by the authors. Thirty studies were included for synthesis.</p> Results <p>Evidence demonstrates measurable concentrations of strontium-90, caesium-137, uranium, and radium in breast milk following environmental contamination events (Chernobyl, Techa River, nuclear weapons testing) and in regions with naturally elevated radioactivity. Transfer rates vary by radionuclide, with strontium-90 showing significant maternal-infant transfer. Biokinetic models indicate dose-dependent accumulation in infant tissues. Limited direct evidence exists for specific health outcomes, though theoretical risk assessments suggest potential impacts on hematopoietic development, bone metabolism, and long-term cancer risk.</p> Conclusions <p>While breast milk contamination with radioactive heavy metals is documented in specific contexts, the health benefits of breastfeeding generally outweigh risks except in acute high-exposure scenarios. Gaps remain in understanding long-term neurodevelopmental and growth impacts. Enhanced biomonitoring and longitudinal studies are needed to inform evidence-based public health guidance.</p>