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Short-term toxicity to aquatic invertebrates

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Description of key information

Several non-standard data of low reliability are available that provide information on the acute toxicity of thiourea towards daphnia. Reported EC50 values were determined after 24 to 96 hours and range between 1.8 mg/L and 4000-6000 mg/L. 
Test duration in standard guidelines is 48 hours. Deviations will make comparison with results from other studies difficult even when these studies are of good quality (e.g. Daphnia sp EC50 results are commonly reported at 24 hours compared to the standard 48hours).
As the study conducted by Nusch (1982) is a guideline study with standard test duration, the study will be used in the assessment of short-term effects of thiourea. As data on the long-term toxicity of thiourea to invertebrates are available that can be used for classification & labelling as well as for the hazard assessment, the risk assessment is based on the long-term toxicity data where appropriate.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
35 mg/L

Additional information

Several non-standard data of low reliability are available that provide information on the acute toxicity of thiourea towards daphnia. The test duration is considered critical information in deciding reliability of a study and must be reported. These do vary by study and range between 24 and 96 hours:

Brocker et al. (1984; cited in the BUA Stoffbericht 179) and Friesel et al. (1984) use a total test duration of 24-h and report EC50 values of 4000 -6000 mg/L and 5.6 mg/L, respectively. Schmidt-Bleek et al. (1982), who do not report the exposure duration, found an EC50 of 110 mg thiourea /L.

Only one study (Nusch 1982) is available that reports effects after 48h, that were determined according to Gerrman national standard (DIN 38412 part 11). The EC50 (48 -h) under the conditions of this study is 35 mg/L.

The 96-h EC50 reported by NAPM (1974) is 1.8 mg/L.

Test duration in standard guidelines is 48 hours. Deviations will make comparison with results from other studies difficult even when these studies are of good quality (e.g. Daphnia sp EC50 results are commonly reported at 24 hours compared to the standard 48hours). As the study conducted by Nusch (1982) is a guideline study with standard test duration, the study will be used in the assessment of short-term effects of thiourea.

As data on the long-term toxicity of thiourea to invertebrates is available that can be used for classification & labelling as well as for the hazard assessment, where appropriate.