Acceptability of aquatic toxicity data for the derivation of water qualityguidelines for metals

The requirement for appropriate quality assurance and quality control in sc ientific measurements makes it essential that the results of toxicity testi ng be acceptable from both a chemical and a biological perspective. Whereas biological aspects have generally been satisfactorily addressed, this has not always been so with respect to chemistry. This paper reviews the areas where toxicity testing protocols for metals in natural waters can be defici ent. These begin with the choice of test container, and include both physic al and chemical aspects of metal-organism interactions that may alter both the bioavailable concentration and the toxic response. The need to consider speciation is emphasized, including the effects of organic complexation, p H, hardness and alkalinity, especially with high metal concentrations and h igh pH values. The difficulties in using uncensored toxicity data from the literature for the development of water quality guidelines are discussed.