ABSTRACT
The use of statistical methods to support risk assessment of chemicals and the derivation of environmental quality criteria in Europe followed a course that, in hindsight, was quite independent from the developments in North America. This was because the earlier publications in North America were reports of the Environmental Protection Agency, which at that time were not widely distributed in Europe (U.S. EPA, 1984b; U.S. EPA, 1985a). Conversely, the first papers published by European authors were in journals that were not well known by North American scientists involved in environmental policy. The first common element to the continents was that policy makers involved in environmental management, i.e., chemicals management and water quality management, drove these developments. In those days, the protection of the aquatic environment was a clear common goal of people working in the two fields. In the early 1990s the attention shifted toward other environmental compartments such as aquatic sediments and soils. The second common element was the question: What assessment factor should be used if many chronic aquatic effect concentrations are available? Normally, an assessment factor of 10 was applied to the lowest of a few no-observed-effect concentrations (NOECs) or LC
values to arrive at a concern level for the aquatic environment (U.S. EPA, 1984b). But what should one do if many NOECs or LC
values are available? It is
quite evident that with increasing information uncertainty reduces; that is, a more reliable estimate can be made when more acute or chronic single-species toxicity data are available. In such situations, applying an assessment factor of 10 to the lowest value can be seen as a punishment for large sample sizes.
