The Institute for Radiation Protection and Nuclear Safety conducts research projects to localize, quantify and trace radionuclides in our environment and theirs impacts on our heath. IRSN’s mass spectrometry platform, PATERSON, is equipped with state of art technologies for radionuclide quantification, element speciation determination and isotope imaging capabilities. One of the platform’s key pieces of equipment is the SIMS 7FE7 designed for microscale isotope imaging in various matrices, including biological and environmental samples. To assess health risks induced by internal contamination, it is crucial to improve the knowledge and understanding of transfer mechanisms and radionuclides’ fate in the body. Such contamination can occur during occupational, environmental, and/or medical exposure, in both routine and accidental situations. Internal contamination by radionuclides lead to biological effects induced mainly by ionizing radiations. SIMS imaging can be used to identify the microdistribution of radionuclides in renal tissue. Precision of this technique allow to localize radionuclides partitioning into the kidney cells, especially uranium accumulation into nuclei of cell. More recently, SIMS 7FE7 applications in the environmental field are increasing, particularly for microscale characterization of environmental phases containing radionuclides. The SIMS microscope is useful to study the spatial distribution of isotopes on environmental particulate phases present in sediments and soils contaminated by radionuclides. SIMS imaging and isotope ratios are providing invaluable information on the origins of pollution sources in the environment, distinguishing between natural processes and anthropogenic activities. SIMS outputs allow to highlight anthropogenic signatures which is essential in environmental risk assessments. The usefulness of SIMS in IRSN's radiation protection research will be illustrated through two specific examples: first, the microdistribution of uranium study in renal tissue to explore the potential relationship between the uranium contamination and potential risk of kidney pathology; and secondly, by the relevance of stable Pb isotopes analysis to trace sources of pollution from radioactive materials in the environment.