Problems associated with selecting the most sensitive species for toxicity testing

Abstract

When the field of aquatic toxicity testing began its first major expansion about 40 years ago, it was uncommon to use more than one test species (usually a fish). Later, it became customary to use individual microorganisms (usually algae) and macroinvertebrates as well. Most attention was then given to the response of the most sensitive species in that test series when calculating the ‘biologically safe’ concentration acceptable for use in natural systems. However, in recent years, there has been an attempt to equate the most sensitive species in a laboratory test series to the most sensitive species in natural systems. Since laboratory test species represent only a tiny part of natural systems and since response variability is well established, that can be a dangerous assumption. The purpose of this discussion is to re-examine the scientific support for this practice.