DISCLAIMER: The present Project Deliverable has been submitted to the European Commission for review. The information and views set out in this report are those of the author(s) and do not necessarily reflect the official opinion of the European Union. Neither the European Union institutions and bodies nor any person acting on their behalf may be held responsible for the use which may be made of the information contained therein. This policy brief argues about the need to better connect Citizen Social Science (CSS) with Sanitation Policy in the Matanza-Riachuelo Basin. This is justified by both the complexity of the socio-environmental problems at stake, and the participatory mandate of national and international regulation regarding environmental policy. We explored the visions of national, provincial and municipal authorities in the basin regarding benefits and challenges of enhancing links with CSS initiatives. We found optimism regarding the potential of these links, especially in relation to policy responsiveness and community empowerment associated to the participatory nature of CSS. However, we also found several challenges for its actual uptake, which were discussed with policy makers all along the research cycle of the Research and Innovation Action and more in depth during the transformation to action phase. Based on these discussions we co-produced several policy options that are described here together with concrete policy recommendations.