Aquatic examples, toxicological

The selection and prioritization of substances for which EQSs are required is generally based on both scientific and political criteria. Scientific criteria include the intensity of use of a substance and its occurrence in the environment (i.e., the likelihood of aquatic exposure) as well as information about its (eco)toxicological properties. Thus, a strong driver might be if a substance belongs to the group of persistent, bio-accumulative, and toxic (PBT) chemicals. Examples can be found in the COMMPS procedure (Fraunhofer IUCT 1999) as well as in the Australian, Canadian, and US approaches, all of which are summarized in Table 4.2. 

Eganhouse, 1997). This field emphasizes not only those compounds with potential toxicological properties, but also the geological systems accessible to the biological receptors of those hazards. Hence, the examples presented in this chapter focus on hydrocarbons with known health and ecological concern in accessible shallow, primarily aquatic, environments. 

The plan of this chapter is as follows After briefly introducing some basic concepts in environmental QSARs, the characteristic use of QSARs in aquatic toxicology will be discussed and their advantages and limitations will be presented by way of various examples. 

Other important toxicological con tarn in ants that can be found in waste-waters are metals. Toxic heavy metal ions are introduced to aquatic streams by means of various industrial activities viz. nfrning, refining ores, fertilizer industries, tanneries, batteries, paper industries, pesticides, etc., and possess a serious threat to the environment. The major toxic metal ions hazardous to humans as well as other forms of hfe are Cr, Fe, Se, V, Cu, Co, Ni, Cd, Hg, As, Pb, Zn, etc. These heavy metals are of specific concern due to their toxicity, bioaccumulation tendency, and persistency in nature [190]. The SLM technique has been widely apphed for the transport and recovery of almost ah important metals from various matrices an exceUent review of ah aspect of metal permeation through SLM (covering both theoretical and practical considerations) is available [191]. Here, only some selected recent examples of the use of SLM for metal separation whl be presented. 

A relatively broad variety of aquatic toxicity studies exists for nitro-substituted phenol, toluene, and benzene explosives and related compounds, but very little toxicological information is available for tetryl, cyclic nitramines, and the other energetic compounds discussed in this chapter. Several explosives, such as tetryl, are no longer manufactured and are, therefore, of diminishing environmental concern, although their persistence and the nature, stability, and toxicity of their breakdown products is not understood in sufficient detail and should be further investigated. A variety of other energetic compounds, for example, perchlorates, are used in military operations, and due to environmental concerns with their release, additional studies on their fate and effects in aquatic systems are recommended. 

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