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The acute aquatic toxicity of 1,2-dichloroethane to fish has been investigated in several species of fresh water fish. In the most reliable study the 96 -hour LC50 was 136 mg/L under flow-through conditions with Pimephales promelas with analytical monitoring.

Most of the remaining available studies are static or semi-static studies and most of them are conducted without analysis of the test concentrations. These tests are not considered for the assessment due to the high volatility of 1,2-dichloroethane. In an experiment with a static design, the material showed a minimum 96 h LC50 of 66 mg/L to Micropterus salmoides with analytical monitoring (but significant, variable and too high vehicle concentrations); a maximum 96 h LC50 of 430 mg/l in a closed static test with Lepomis macrochirus (Rinehart, W.E. 1971; Buccafusco et al. 1981).

Similar to the short term toxicity of fish, the acute toxicity of 1,2-dichloroethane to aquatic invertebrates was studied in several static and semistatic tests. Only such tests were considered for the assessment that were performed in closed systems or with analytical monitoring of the test substance concentration. The lowest EC50 value for freshwater invertebrates of 160 mg/l was found in a 48h test with Daphnia magna. In this test the substance concentration was analytically monitored. Additional investigations with marine invertebrates resulted in the lowest endponit for the species Artemia salina. The 24h- EC50-value was 36 mg/l. Although these studies indicate a higher risk they do not satisfy the guideline requirements, as the amount of solvent (acetone) used in the test was variable in the differtent concentrations and higher than the requested 0.1 mL/L. Further on, different water salinities were used as further stressor.

The toxicity of 1,2-dichloroethane was investigated in different algal species. The 96 h measured EC50 of 166 mg/l was obtained on Scenedesmus subspicatus, tested in a system controlling volatile losses (capped vessels) and is considered to be the lowest EC50-value for growth inhibition of algae. A corresponding NOEC is not available but, based on this EC50, it is, however, unlikely that the NOEC would be lower than NOEC obtained on Daphnia magna (28d NOEC of 11 mg/l for reproduction).

In addition, long-term tests are available with fish and Daphnia. In an embryo-larval study with Pimephales promelas a 32d-MATC related to wet weight of 29 - 59 mg/l based on measured concentrations was found under flow-through conditions. Eggs used were 24 hr old (Ahmad 1984). From the MATC a NOEC of 29 mg/l can be derived. In a 28d-reproduction test conducted under semistatic closed conditions with D. magna the LOECvalues determined for reproduction and growth were 21 ± 1.7 and 72 ± 4.8mg/l and the NOECvalues determined for reproduction and growth were 11 ± 0.8 and 42 ± 2.4 mg/l (based on measured concentrations), respectively (Call et al. 1983).

The lowest effect value of 11 mg/l was found in a long-term test with Daphnia magna. This value is used as basic value for the derivation of the PNECaqua. As long-term tests with fish and daphnids are available and as it can be assumed that algae are not more sensitive to 1,2-DCE than daphnids an assessment factor of 10 is applied resulting in a PNECaqua of 1.1 mg/l.

In the cell multiplication inhibition test the effect of 1,2-dichloroethane on micro-organisms was studied. In the bacterial strain Pseudomonas putida the toxicity threshold (TT) after a16 hr exposure period has been determined to be 135 mg/l (Bringmann and Kuehn 1976; 1977; 1980). In the course of a closed bottle test the toxicity towards activated sludge from a local WWTP was studied. The cumulative oxygen demand has been measured over 3 hr and the concentration leading to a 50 % reduction in oxygen consumption was determined. A 3 hr IC50 of 35.5 mg/l was derived from this investigation indicating slight and transient toxicity on activated sludge (Tang et al. 1990).