Overview of the MODARIA programme (and comments on implications for future programmes of work) .

The International Atomic Energy Agency (IAEA) has organised programmes on the development, comparison and testing of environmental assessment models and approaches for estimating the radiation exposure of humans and wildlife since the 1980s. The latest of these programmes was called MODARIA (Modelling and Data for Radiological Impact Assessment) and was run in two phases from 2012 to 2015 (MODARIA I) and 2016 to 2019 (MODARIA II). Both phases of the MODARIA programme had the overall objective to improve capabilities in the field of environmental transfer of radionuclides and public and non-human biota exposures assessment, by means of acquisition of improved data for model testing and comparison, reaching consensus on modelling philosophies, approaches and parameter values and building an international forum for the exchange of information. This paper provides an overview of the work undertaken during both phases of the MODARIA programme and its outputs. The overall aims and objectives of a new programme to follow on from MODARIA are described.