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Daphnia magna reproduction tests were performed with C(10), C(12), C(14) and C(15) alcohols to establish a structure-activity relationship of chronic effects of long-chain alcohols. The data generation involved substantial methodological efforts due to the exceptionally rapid biodegradability of the test substances and the need to test as close as possible to their water solubility limits. Test concentrations were determined by GC-MS before and after test solution renewal. Whereas apparent toxicity based on survival and reproduction increased with increasing C-chain lengths up to C(14), observations of toxicity to C(15) alcohol were not in line with lower chain lengths due to the lack of toxicity below the level of water solubility. When omitting C(15), the slope of most (Q)SARs approach -1, being consistent with the expectation of a non-polar narcotic mode of action. Further testing at higher chain lengths is not sensible due to progressively lower solubility, at remaining biodegradability. Effects on mortality and reproduction are not expected below the level of water solubility.

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Environmental risk assessment is a key feature of regulations controlling the placing of new, and the maintenance of existing, chemicals products in the market place. For example, European Commission Directive 93/67/EC on Risk Assessment for New Notified Substances and Commission Regulation (EC) No. 1488/94 on Risk Assessment for Existing Substances requires that risk assessments be carried out for new and existing substances in the European Community. The process of environmental risk assessment seeks to determine the balance of probability of species and communities being damaged by chemical releases. The process relies upon a valid estimation of a predicted environmental concentration (PEC) in relevant environmental compartments and a predicted no effect concentration (PNEC) below which the organisms present in that compartment are unlikely to be significantly affected. If the PEC exceeds the PNEC there is a potential for damaging effects to occur. This article focuses on the determination of PNECs for risk assessment. Methods for determining a PNEC described in OECD Monograph 26 (1989, Report of the OECD Workshop on Ecological Effect Assessment, Paris, France, have been applied to data derived for the four chemicals lindane, 3,4-dichloroaniline, atrazine, and copper in a series of collaborative research projects funded by the European Commission.

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Two collaborative research projects were designed to develop and validate methods for determining the chronic effects of xenobiotics in freshwater ecosystems. The work reported here focuses on the development of methods for measuring effects on fish, invertebrates, and algae in outdoor artificial streams. 3,4-Dichloroaniline (3,4-DCA), has been used as a reference xenobiotic in two artificial stream experiments. The first used five stream channels: a control and treatments ranging from 70 to 2400 microg/liter. The second used eight stream channels--a control and treatments ranging from 0.45 to 4700 microg/liter and four coupled, 510-liter-capacity, downstream ponds-a control and treatments of 1.7, 37, and 820 microg/liter. Effects on the biota of the stream channels and the downstream ponds were examined using a range of sampling techniques and in situ toxicity tests.

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This article presents a summary of a collaborative research program involving five European research groups, that was partly funded by the European Commission under its Environmental Research Program. The objective of the program was to develop aquatic toxicity tests that could be used to obtain data for inclusion at Level 2 of the Risk Evaluation Scheme for the Notification of Substances as required by the 7th Amendment to EC Directive 79/831/EEC. Currently only a very limited number of test methods have been described that can be used for this purpose and these are based on an even smaller number of test species. Tests based upon algae (Chlamydomonas reinhardi, Scenedesmus subspicatus, and Euglena gracilis), protozoa (Tetrahymena pyriformis), rotifera (Brachionus calyciflorus), crustacea (Gammarus pulex), and diptera (Chironomus riparius) were developed. The tests encompassed a range of end points and were evaluated against four reference chemicals: lindane, 3, 4-dichloroaniline (DCA), atrazine, and copper. The capacity of the tests to identify concentrations that are chronically toxic in the field was addressed by comparing the effects threshold concentrations determined in the laboratory tests with those determined for similar and/or related species and end points in stream and pond mesocosm studies. The lowest no-observed-effect concentrations (NOEC), EC(x), or LC(x) values obtained for lindane, atrazine, and copper were comparable with the lowest values obtained in the mesocosms. The lowest chronic NOEC determined for DCA using the laboratory tests was approximately 200 times higher than the lowest NOEC in the mesocosms.

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Aquatic toxicity tests were originally designed for individual compounds that are soluble and stable in water. For sparingly soluble substances that are not toxic at the solubility limit, the issue is whether tests should be performed with insoluble test substance present. Based on a literature evaluation of the physiology of uptake, it was concluded that only the dissolved fraction is available for uptake and that the insoluble test substance may introduce artifacts that aggravate data interpretation. Therefore, toxicity tests should be conducted only up to the solubility limit. Testing of volatile, unstable, or adsorptive substances is complicated by the ability to keep exposure concentrations relatively constant. For these, appropriate test protocols including adequate design of the dosing systems must be employed. For test medium preparation, physical methods and, where necessary, use of low concentrations of certain solvents are recommended to support handling and speed of dissolution. However, recommendation is made against the use of dispersants. Water-accommodated fractions are recommended as one approach for dosing multicomponent substances. Interpretation of observed 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.

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