the use of radiopharmaceuticals for diagnostic or therapeutic purpose can lead to the release of radioactive liquid wastes into the wastewater network. The aim of this study is to identify and quantify the presence of the radionuclides used in nuclear medicine in sewage treatment plants and also to estimate their impact on aquatic ecosystems. Methods: the radioactivity monitoring in sewage treatment plants was performed using an average sampling or a gamma probe for continuous measurement of radioactivity. Laboratory studies were then conducted on fish to assess the environmental impact of two largely used radiopharmaceuticals. Results: the radio-isotopes detected in the sewage treatment plants are iodine 131 and technetium 99m. The irregular appearance of radioactivity peaks did not allow an average sampling to be used for the release monitoring. Consequently, a continuous monitoring is recommended. In the case of the laboratory studies, the two studied iodine radiopharmaceuticals were NaI and MIBG. Results showed that NaI was mainly distributed in the thyroidal follicles whereas MIBG was found in adrenergically innervated tissues. These compounds were quickly depurated (around 80% in 2 days) and no genotoxicity was observed for the studied doses.