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Ecotoxicological information

Long-term toxicity to aquatic invertebrates

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Description of key information

The chronic toxicity of Imidazolidine-2-thione was evaluated with Daphnia magna in a study performed according to the OECD 211 guideline. The NOEC-21d was estimated equal to 3.2 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
3.2 mg/L

Additional information

The chronic toxicity of ETU was firstly evaluated with Daphnia magna in a study performed with no guideline (Van Leeuwen, 1985). The effects of prolonged exposure (21 days) to ETU were examined on survival, fecundity and growth of Daphnia Magna. The EC50 -21d was estimated equal to 18 mg/L. Inhibition of population growth was observed at levels below those which caused a significant reduction in survival.

A significant reduction in mean carapace length of 21-day-old daphnids was generally detected at levels comparable with LC50 value. With ETU, the carapace length was 1x10^4. However no NOEC was estimated during this study.

In order to refine the PNECs, a 21-day Daphnia magna reproduction study was conducted to determine the effects of exposure to Ethylenethiourea (CAS 96-45-7) on Daphnia magna reproduction and survival in accordance with the OECD Chemicals Testing Guideline No.211 Daphnia magna Reproduction Test (adopted October 2012). The definitive test was conducted at nominal concentrations of 0.10, 0.32, 1.0, 3.2 and 10 mg/L. Actual concentrations did not differ by more than 20% of the nominal concentrations. The test was conducted using a semi-static design with renewal of the test media three times a week. The NOEC for reproduction was considered to be 3.2 mg/L.