This publication was developed as part of the IAEA’s MODARIA I and MODARIA II programmes, which focus on modelling and data for radiological impact assessments. It presents the outcomes of Working Group 4, which considered the update and improvement of distribution coefficient (Kd) values used in environmental models for exposure assessment for soil, freshwater, and marine systems. As part of this effort, Kd datasets for soils and freshwater sediments were compiled. These datasets include associated chemical, physical, mineralogical, and other ancillary properties, along with detailed methodological guidance to support end users in selecting appropriate Kd values for their specific applications. For marine sediments, Kd data were compiled using sources from Japan, the Baltic Sea, and the IAEA’s Marine Radioactivity Information System (MARIS) database. These values were then compared with those published in the IAEA Technical Reports Series No. 422, Sediment Distribution Coefficients and Concentration Factors for Biota in the Marine Environment. This publication is intended for environmental regulators, scientists, modellers and assessors.