This research examined how the medicinal chaga mushroom accumulates and distributes radioactive potassium in nature. The study found that wild chaga naturally concentrates potassium-40 in its outer layers, especially when exposed to sunlight. This information is important for understanding both the beneficial and potentially concerning aspects of chaga as a medicinal mushroom. Impacts on everyday life: • Helps ensure safety standards for commercial chaga products • Provides guidance for optimal harvesting of wild chaga • Improves understanding of how medicinal mushrooms interact with their environment • Assists consumers in making informed decisions about chaga supplements • Contributes to better quality control in natural medicine products