The rate at which atoms of radioactive sources disintegrate is measured in:

The rate at which atoms of radioactive sources disintegrate is measured in Curies. A Curie is a unit of radioactivity defined as 37 billion disintegrations per second and is named after Marie Curie, who conducted pioneering research on radioactivity. This unit provides a clear standard for measuring the activity of radioactive materials, making it essential for understanding and managing radiation exposure in both environmental health and public safety contexts.

Grays measure absorbed radiation dose, Sieverts account for the biological effects of radiation, and Radon levels refer specifically to the concentration of radon gas in an environment, rather than the disintegration rate of radioactive atoms. Thus, while all these units are important in radiation science, the Curie is specifically designated for measuring the disintegration rate of radioactive materials.