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Toxicity to soil microorganisms

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Reference
Endpoint:
toxicity to soil microorganisms
Data waiving:
other justification
Justification for data waiving:
other:
Justification for type of information:
JUSTIFICATION FOR DATA WAIVING
In accordance with the Guidance on information requirements and chemical safety assessment Chapter R.7c (Endpoint specific guidance Version 3.0, June 2017) the performance of the test on toxicity to soil microorganisms has been waived.
The test substance has a very low water solubility of 0.021 mg/L at 20 °C (rf. to IUCLID section 4.8). Short and long term studies for the aquatic compartment are available showing no adverse effects up to the solubility limit of the test substance.

Aquatic acute toxicity
48 h, EC50 (Daphnia magna): > 0.69 mg/L
72 h, ErC50 (Algae): > 0.76 mg/L (measured)
96 h, LC50 (Fish): > 1 mg/L (measured)

Aquatic chronic toxicity
21 d, EC10 (Daphnia magna): 0.027 mg/L (estimated)
72 h, NOErC (Algae): 0.76 mg/L (measured)
21 d, NOEC (Fish): > 0.94 mg/L (measured)

Prolonged exposure of Daphnia magna to the test substance resulted in a slight reduction in the numbers of young produced at the three highest exposure levels (0.045, 0.17 and 0.53 mg/L). No other adverse effects on survival or reproduction were observed. It should be recognized that the concentrations required to cause impairment of reproduction are unlikely to occur in the environment due to the low solubility of the test substance in water (0.021 mg/L). The "NOEC" based on measured concentrations is above the water solubility value of the test substance.

Furthermore no effects were observed in a respiration inhibition test according to OECD 209.

For the terrestric compartment acute studies with two different taxa with different pathways of exposure are available. Both short term studies in earthworms and plants were performed in accordance with OECD guidelines and good laboratory practice (GLP). No effects were observed up to the highest tested nominal doses (1000 ppm for earthworms and 100 mg/kg soil for plants). The PNECsoil resulted in 0.1 mg/kg soil dw. Using the equilibrium partitioning method a higher result would be obtained (1.16 mg/kg soil dw). For the risk assessment the worst case of 0.1 mg/kg soil dw was used.

In the chemical safety assessment it is further shown that the PEC/PNEC ratio for the soil compartment is below 1. An additional study in soil microorganisms was therefore regarded as scientifically unjustified and the test has been waived.

Description of key information

scientifically unjustified

Key value for chemical safety assessment

Additional information

In accordance with the Guidance on information requirements and chemical safety assessment Chapter R.7c (Endpoint specific guidance Version 3.0, June 2017) the performance of the test on toxicity to soil microorganisms has been waived based on available studies for short and long term aquatic toxicity as well as short term toxicity on earth worms and plants. In the chemical safety assessment it is further shown that the PEC/PNEC ratio for the soil compartment is below 1. An additional study in soil microorganisms was therefore regarded as scientifically unjustified and the test has been waived.