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Short-term toxicity to aquatic invertebrates

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Description of key information

A key study is presented performed according to OECD guideline 202. The lowest 48h EC50 was determined to be 2.8 mg/l. The SIDS dossier reports fourteen different sources for acute toxicity to aquatic invertebrates in support of the key study.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
2.8 mg/L

Additional information

A key study is presented for the acute toxicity of 2,4-dichlorophenol to aquatic invertebrates (Daphnia magna). This study was performed according to OECD guideline 202, Daphnia sp. Acute Immobilisation Test, Annex V EEC C2 Acute Toxicity for Daphnia and ToxCalc version 5.0 "Comprehensive Toxicity Data Analysis and Database Software". The study was conducted to GLP. This study determined the 24 hour EC50 to be 5.7 mg/l, the 48 hour EC50 to be 2.8 mg/l and the 48 hour NOEC to be 1.6 mg/l. 100% immobilisation of the daphnia over 48 hours was observed at 4.0 mg/l.

The SIDS dossier reports 14 different publications regarding the acute toxicity of 2,4-Dichlorophenol to aquatic invertebrates, leading to 9 EC50values at 24 or 48 hours on Daphnia magna. Those assigned a reliability of 2, valid with restrictions, are recorded as endpoints.

Seven references were assigned validity 2, three a reliability of 3 and one a reliability of 4. Two test results can be used as they were performed in Daphnia magna for 48 hours in a way close to standardised protocols.

The lowest LC50value was obtained by testing the 2,4 -dichlorophenol on Daphnia magna according to the DIN 38412 method. The LC50(48 hours) value obtained was 1.4 mg/L. In another publication, 2,4 -dichlorophenol was shown to be slightly more toxic to Daphnia magna as pH values increased.

It has to be noted that in these studies, no analytical monitoring of the test concentrations was performed, but since the results were consistent with each other and some of these studies were conducted in the dark (avoiding the photodegradation of the 2,4 -dichlorophenol), the most reliable ones were assigned a validity 2. As no studies were conducted with analytical monitoring, the real effect concentration may be lower than the nominal one.

The sensitivity of the crustacea Paleomonetes pugio is in the same range (96h-EC50= 2.2-2.6 mg/L), whereas Tisbe battagliai seems less sensitive than Daphnia magna (24h-EC50= 16 mg/L).

Given that a key modern day study is available the EC50 (48 hours) for 2,4 -dichlorophenol to aquatic invertebrates is 2.8 mg/l.