Dr. Rethy K. Chhem joined the International Atomic Energy Agency (of the United Nations) in November 2008. He is currently the Director of the Human Health Division (Nuclear Medicine, Diagnostic Radiology, Medical Radiation Physics and Radio-oncology).

The division conducts hundreds of programmes in developing countries in the fields of radiology, nuclear medicine, medical physics, radio-oncology and nuclear sciences/nutrition. Dr. Chhem also serves on the Steering Committee of the IAEA/WHO joint programme for Cancer Control. He represents the IAEA at UNSCEAR (UN Scientific Committee on the Effects of Atomic Radiation)