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Ecotoxicological information

Toxicity to terrestrial plants

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Key value for chemical safety assessment

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The Guidance on information requirements and chemical safety assessment, Chapter R.7C: Endpoint specific guidance (November 2014), section R. 7.11.6.3, Table R.7.11-2, page 145, specifies the information needed to waive the terrestrial studies based on soil hazard categories. The registered substance has a log Pow <3 and exhibits a good potential for inherent biodegradability. Therefore, accumulation and persistence of the registered substance in soil and organisms is very unlikely.  Furthermore, although the registered substance might adsorb to soil (estimated log Koc = 3.8), it is not expected to cause adverse effects on terrestrial organisms based on a PNEC soil derived from a chronic earthworm study. Consequently further terrestrial toxicity tests are not needed.

 Further argumentation for the waiving of the terrestrial plant study:

- In acute aquatic tests, fish and daphnids were by a factor of > 35 more sensitive than aquatic algae (fish LC50: 0.88 mg/L, acute Daphnia EC50: 2.4 mg/L, algae ErC50 93 mg/L). This is also valid when comparing chronic data (EC10 daphnids: 0.15 mg/L, ErC10 algae: 7.8 mg/L.). Therefore aquatic algae are not the relevant species for the aquatic risk assessment.

- Based on the results from the aquatic environment, i.e.,invertebrates are more sensitive thanalgae, it canalso be assumed that the terrestrial plants are less sensitive compared to terrestrial invertebrates. A chronic earthworm study resulted in a NOEC of 104 mg/kg dw. Taking into account theaquatic tests, this NOEC is considered to be conservative. This NOEC value resulted in PEC/PNEC << 1 for the soil compartment in every usage covered by the chemical safety assessment. Hence, there is no indication that a plant test will provide further information for the risk assessment of this substance.

- If, however, a terrestrial plant test would be performed, data from two trophic levels would be available and hence an assessment factor of 50 instead of 100 could be used for the risk assessment according to the current guidance documents.  Assuming that the plants are not more sensitive than the earthworms, this would result in a higher PNEC. Hence, not performing the terrestrial plant test is considered to be conservative.