1. As global human populations continue to grow uncontrollably, there is a foreseeable medium to long-term need for the utilization of deep ocean environments for disposal of waste materials to maintain sustainability of global environmental resources. 2. The assimilative capacity of deep ocean ecosystems is likely to be high relative to the quantities of waste that cannot be dealt with through alternative options such as waste minimization, recycling and incineration. 3. Deep ocean disposal may not be an acceptable option for the disposal of industrial organic compounds, which are persistent in the environment but for which alternative destructive procedures are available. 4. The choice of either a dispersive or accumulative regime for a disposal will need be based on the characteristics of the waste. Waste that is biologically or chemically degradable may best be dispersed. 5. Present knowledge of deep ocean ecosystems would suggest that disposal of inert, metal-rich, or even organic-rich wastes into accumulative regimes on the floor of the abyssal ocean would not create major deleterious impacts on living resources or other uses by Mankind of the oceans. Thus, under the present definition adopted by the Law of the Sea Convention this would not constitute large-scale pollution. 6. These tentative conclusions need to be evaluated by appropriately scaled experiments. Results from small-scale experimental procedures, based on the disposal of a few tonnes of waste and effecting a few square metres of sea-bed, cannot be extrapolated to predict confidently the impact of industrial scale disposal. Experiments approaching a tenth the size and extent of a full industrial exercise will be needed, but conducting such an experiment will not, in itself, carry significant environmental risk. 7. There are also some basic biological questions, mostly concerning the diversity of benthic assemblages and the processes that maintain their diversity, that will need to be resolved before deep-ocean disposal could be adopted. 8. There are major socio-economic problems about the global management of the abyssal ocean as a non-living resource which will have to be addressed internationally.
