Satisfying human needs requires an anthropogenic material turnover. After utilization, materials either remain in the anthroposphere in terms of recycling products, or they leave the anthroposphere in terms of waste and emission flows. The last two enter downstream sinks, man-made and natural ones. The problem is that material flows to natural sinks may cause risks for human and environmental health. To avoid overloading, several assessment frameworks have been put forward. In an economy-wide perspective, a single score indicator focusing on substances that leave the anthroposphere to regional sinks is missing. To overcome this gap, the thesis aims to develop a new indicator and to compute the score for selected case studies. To achieve these goals, four steps are needed. First, the indicator is defined as the environmentally acceptable mass share of a substance in material flows that leave the anthroposphere to downstream sinks. The resulting score ranges between 0% as worst case and 100% as best case. Second, a methodology to determine the indicator components is presented, including (i) inventories based on substance flow analysis, and (ii) impact assessment based on a distance-to-target approach. Third, the framework developed is applied in three case studies including copper (Cu) and lead (Pb) on an urban scale (City of Vienna) and Perfluorooctane Sulfonate (PFOS) on a national scale (Switzerland). Fourth, recommendations are given for increasing the indicator score by means of sink load reduction or enhancement of sink capacities. The following results are obtained: In Vienna, 99% of Cu mass flows to regional sinks are acceptable. However, the 0.7% of Cu entering urban soils and the 0.3% entering receiving waters surpass acceptable levels. In the case of Pb, 92% of all mass flows to sinks prove to be acceptable, and 8% are disposed of in local landfills with limited capacity. For PFOS, 96% of all flows to sinks are acceptable. 4% cannot be evaluated due to a lack of quality criteria, despite posing a risk for human health and the environment. The examples demonstrate the need for: (i) enhanced regional landfill capacities or increased recycling rates, (ii) regional standards for assessing substance flows to urban soils and receiving waters, (iii) appropriate data of good quality, and (iv) the extension of the methodology to include exports to sinks in the hinterland. The new indicator is of relevance for managing wastes and emissions because it identifies substance flows to sinks that observe or neglect quality criteria, or that cannot be assessed due to missing knowledge. Moreover, it serves for monitoring the performance of waste and environmental management within a region, and for comparing the performance with other regions. For strategic decisions such as design and evaluation of policies, the indicator allows an examination of the effectiveness of directing substance flows to appropriate sinks. Finally, the indicator aggregates complex information into an easy to understand score and is therefore highly instrumental for communicating scientific research to decision makers and the public.