AQUATIC TOXICITY TESTING OF SPARINGLY SOLUBLE, VOLATILE, AND UNSTABLESUBSTANCES AND INTERPRETATION AND USE OF DATA

Aquatic toxicity tests mere originally designed for individual compoun ds that are soluble and stable in mater, For sparingly soluble substan ces that are not toxic at the solubility limit, the issue is whether t ests should be performed with insoluble test substance present, Based on a literature evaluation of the physiology of uptake, it was conclud ed that only the dissolved fraction is available for uptake and that t he insoluble test substance may introduce artifacts that aggravate dat a interpretation. Therefore, toxicity tests should be conducted only u p to the solubility limit, Testing of volatile, unstable, or adsorptiv e substances is complicated by the ability to keep exposure concentrat ions relatively constant. For these, appropriate test protocols includ ing adequate design of the dosing systems must be employed. For test m edium preparation, physical methods and, where necessary, use of low c oncentrations of certain sol rents are recommended to support handling and speed of dissolution, However, recommendation is made against the use of dispersants, Water-accommodated fractions are recommended as o ne approach for dosing multicomponent substances, Interpretation of ob served effects depends on appropriate test medium preparation, correct measurement and expression of exposure levels, and differentiation of true toxicity from indirect physical effects of the substance, or the toxicity of impurities. (C) 1998 Academic Press.