When FDA tests food for radioactive contamination, it measures how much radiation is released by radioactive materials that are not expected to be naturally present.
Radioactive materials are substances that release high energy particles or electromagnetic radiation. These high energy particles or electromagnetic radiation are emitted by unstable atoms as they go through transition to a more stable state. The energy that is released from radioactive materials is called radiation. Radioactive materials can be natural (for example, some rocks in the earth are radioactive) or man-made.
