Introduction

The movement of materials from land to sea is an inevitable part of the hydrological cycle and of all geological processes. Nevertheless, human activities have both concentrated and increased these flows as a result of the creation of large human settlements, the development of industrial processes and the intensification of agriculture. Until the 1960s, many took the view that the oceans were capable of assimilating everything that humans wanted to discharge into the oceans. In the 1960s, this view came to be seen as out-dated (UNESCO, 1968). Following the 1972 Stockholm Conference on the Human Environment, many steps were taken to address issues of marine pollution. During the preparations for the United Nations Conference on Environment and Development (“the first Earth Summit”), held in Rio de Janeiro, Brazil, in 1992, there was general agreement that, in spite of what had been done, a major initiative was needed to address the problems of landbased inputs to the oceans. As a result, Agenda 21 (the non-binding action plan from the 1992 Earth Summit) invited the United Nations Environment Programme (“UNEP”) to convene an intergovernmental meeting on protection of the marine environment from land-based activities (Agenda 21, 1992). In October 1995, the Global Programme of Action for the Protection of the Marine Environment from Land-Based Activities (GPA) was adopted in Washington, DC. First among the priorities of this Programme was improving the management of waste-water: this concerned not only waste-water containing human wastes, but also waste-water from industrial processes. In addition, a wide range of other source categories also creating problems for the marine environment was identified (UNEP, 1995). The Programme reflected the experience of over twenty years’ work by governments, both individually and through regional seas organizations, to address these problems. Subsequent intergovernmental reviews of the implementation of the GPA show that progress is being made in many parts of the world, but only slowly.

In evaluating the impacts of contamination on the marine environment, there are significant difficulties in comparing the situations in different areas. For many aspects of contamination, evaluating the levels of contamination requires chemical analysis of the amounts of the contaminants in samples of water, biota and/or sediments. Unless there is careful control of the sampling methods and analytical techniques in all the cases to be compared, it is difficult to achieve scientifically and statistically valid comparisons.