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Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

Direct exposure to the terrestrial compartment is not intended. An indirect exposure to the soil compartment via sewage sludge cannot be excluded. Therefore, additional data on terrestrial organisms are provided.

A study on the acute toxicity of the substance to the soil macoorganism Eisenia fetida following OECD guideline 207 resulted in a LC50 >= 1000 mg/kg dw [BAF SE 2011]. Additional studies conducted according to OECD 216 and 217, respectively, investigated long-term effects of the substance on soil microorganisms which also resulted in EC10/EC50 values greater than 1000 mg/kg dw [BASF SE 2012].

Adverse effects of the test substance to terrestrial organisms appeared only with terrestrial plants. A guideline study according to OECD 208 was conducted with three different plant species: Avena sativa, Brassica napus and Vicia sativa. At the end of the exposure period, an EC10 (shoot length) of 15.4 mg/kg soil dw was determined in Brassica napus as the most sensitive endpoint among all observed species and endpoints investigated. The EC10 values for the other two plants species investigated were in fact 148 and 336 mg/kg dw for Vicia sativa and Avena sativa, respectively.

The corresponding EC50 value is 80.4 mg/kg soil dw (based on plant dry weight).

All other EC50 values from other endpoints and species investigated were above this value.

Since the OECD 208 terrestrial plant toxicity study has been carried out in accordance with the ECHA Guidance on information requirements and chemical safety assessment, Chapter R.7. c: Endpoint specific guidance, November 2012, 140ff, Appendix to section R.7.11, Table R.7.11-3 Selected Soil Test Methodologies, which requires a minimum of 3 three test species, the study on Seedling Emerge and Growth (OECD 208) has to be considered as a chronic plant toxicity test and thus the corresponding EC10 value has to be taken into account for the derivation of the PNECsoil.

Based on the available acute data set from three trophic levels (earthworm, soil microflora and terrestrial plants) together with the absence of an experimentally observed bioaccumulation potential (BASF 2006a, 2005a), it is of evidence that terrestrial plants (EC50 of 80.4 mg/kg dw) are the most sensitive taxonomic group at the acute level, whereas both soil microflora organism and earthworm showed no effect at all up to 1000 mg/kg dw (e. g. EC50 is above 1000 mg/kg dw, Table a). Moreover, it can be concluded that terrestrial plants represent the most sensitive taxonomic group in chronic tests too. This was clearly demonstrated by the available chronic toxicity data from the two soil microflora (EC10 >= 1000 mg/kg dw) and the one terrestrial plant study (EC10 of 15.4 mg/kg dw). Thus, taking this information into account, it is very unlikely that an additional chronic toxicity test on earthworm would result in a chronic EC10 value below the value obtained in the toxicity test with terrestrial plants. Therefore, the assessment factor for the derivation of the PNECsoil based on two available chronic toxicity tests (AF of 50) is further lowered down to an assessment factor of 10, which is in accordance with the ECHA Guidance on information requirements and chemical safety assessment, Chapter R.10: Characterisation of dose [concentration]-response for environment, May 2008 (R.10.3.1 Freshwater compartment, p. 17ff, and R.10.6.2. Calculation of PNEC for soil using assessment factors p. 40f).

Table a). Overview on available acute and chronic toxicity data on terrestrial organisms

 

Acute effect level, EC50 [mg/kg dw]

Chronic effect level, EC10 [mg/kg dw]

Earthworm

> 1000 mg/kg dw

>= 1000 mg/kg dw

Soil microflora (nitrogen transformation)

> 1000 mg/kg dw

>= 1000 mg/kg dw

Soil microflora (carbon transformation)

> 1000 mg/kg dw

>= 1000 mg/kg dw

Terrestrial plants

80.4 mg/kg dw

15.4 mg/kg dw

In conclusion, the PNECsoil is derived from the terrestrial plant toxicity study with a corresponding EC10 value of 15.4 mg/kg dw by applying an assessment factor of 10.