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Long-term toxicity to aquatic invertebrates

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Description of key information

 In a weight of evidence approach using two reliable studies, the chronic toxicity to invertebrates (Daphnia magna) of 1,3-dichlorobenzene was determined at a NOEC of 0.5 mg/L after 21 days.

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater invertebrates:
0.5 mg/L

Additional information

Weight-of-evidence approach:

Two studies are available with similar results. Kuehn (1989) reports a 21d-NOEC of 0.5 mg/L and Richter (1983) a 28d-NOEC of 0.69 mg/L. Kuehn was chosen as the key result as they reported the lower value. However, no dose-effect correlation was shown, only the final result. Richter (1983) reported a slightly higher value but reported a dose-effect correlation showing a significant effect at the higest test concentration. Thus, a clear NOEC could be proven.

Invalid study:

Another chronic daphnia study is available (MITI 1996). This study has however significant weaknesses and was therefore not used for the assessment for the following reasons:

1. Now clear data for LOEC and NOEC are presented.

2. Concentration- effect-relation: No clear correlation can be stated in the region of 0.1, 0.32, 0.56 and 1.0 mg/L. The number of offspring varies in the region of 40 to 50 per adult, independantly from the concentration. The number of offspring at 0.56 mg/L was even higher than at 0.1 and 0.32 mg/L.

3. A modifyer was used although the substance has a good water solubility (>100 mg/L) and there is no reason to use the modifyer in the concentration region of 0.1 to 1.8 mg/L. Furthermore, the concentration of the modifyer is not described in the report and thus it is not clear whether the limit concentration of 0.1 mg/L as given by the guideline was exceeded.

4. Two other reliable studies are available with a clear concentration-effect-correlation. Both studies show quite similar results.