Large quantities of products, materials and substances have accumulated in society. This article investigates the dynamic behaviour of these societal reservoirs or stocks in order to explore future emissions and waste streams. We argue that the stock dynamics are mainly determined by its inflow and outflow characteristics. The stock's inflow is determined by socio-economic factors, which can be quantified using regression analysis. Two processes determine the stock's outflow: leaching and delay. Leaching occurs during use and can be modelled as a function of the stock's size. Delay is related to the discarding of products after use and can be modelled as a delayed inflow distributed over time. This approach is illustrated by the case of lead as applied in cathode ray tubes in the European Union (EU). By applying this model to other lead applications and combining the results, the dynamic behaviour of the total lead stock in society can be described. (c) 2004 Elsevier Ltd. All rights reserved.