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Long-term toxicity to aquatic invertebrates

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Description of key information

Three studies are available regarding the long-term toxicity of thiourea to invertebrates. These three studies are rated Klimisch III due to deficiencies regarding the documentation of the methods and results. However, as all three studies are reporting results for the long-term toxicity of thiourea to Daphnia magna that are in the same range, the studies are used in the assessment of thiourea in a weight-of-evidence approach:
- Broecker et al. (1984): NOEC < 0.25 mg/L
- Friesel et al. (1984): NOEC = 0.25 - 1 mg/L
- Boje & Rudolph (1985): NOEC = 0.1 - 0.25 mg/L
Due to precautionary principles the lowest reported result of NOEC (21-d) = 0.1 mg/L is used in the assessment of thiourea.

Key value for chemical safety assessment

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

Additional information

Three studies are available regarding the long-term toxicity of thiourea to invertebrates. These three studies are rated Klimisch III due to deficiencies in documentation of the methods and results. However, as all three studies report results on the long-term toxicity of thiourea to Daphnia magna that are in the same range, the studies are used in the assessment of thiourea in a weight-of-evidence approach.

Friesel et al. (1984) studied the 21-day chronic toxicity of thiourea to Daphnia magna under semi-static conditions. Daphnids were exposed to control and test chemical at several concentrations (no details reported). Three independent test series were conducted. The lowest 21 day NOEC based on mortality of the parent animals and reproduction was 0.25 mg/L. Production of offspring in the treated groups indicated that thiourea had an effect on reproduction at concentrations greater than 0.25 mg/L.

Broecker et al. (1984) also investigated the 21-day chronic toxicity of thiourea to Daphnia magna under semi-static conditions. Daphnids were exposed to control and test chemical at concentrations 0.2, 0.8, 2.5, 8, and 25 mg/L. The lowest 21 day NOEC based on reproduction was < 0.25 mg/L. Production of offspring in the treated groups indicated that thiourea had an effect on reproduction at concentrations greater than 2.5 mg/L.

Boje & Rudolph (1985) report the following results for the 21-day chronic toxicity of thiourea to Daphnia magna under semi-static conditions: The lowest 21 day NOEC based on lethal effects, reproduction and other observed effects was 0.1 mg/L.

Applying the precautionary principle, the lowest reported NOEC (21 d) of 0.1 mg/L is used in the hazard assessment of thiourea.