Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

The following terrestrial tests have been performed. Below in table the results are summarized.

 Endpoint/species Test guideline   Result  Comment
Reproduction earthworms (Eisenia fetida) OECD TG 222  NOEC28d: 100 mg/kg soil dw (mortality)NOEC28d: 31.6 mg/kg soil dw (body weight)NOEC56d: 31.6 mg/kg soil dw (reproduction) Key study, K1 
 Nitrogen Transformation test OECD 216 

NOEC28d: 100 mg/kg soil dw (nitrate formation rate)

NOEC28d: 100 mg/kg soil dw (nitrate content) 

Key study, K1 
 Terrestrial plan test  OECD 208 EC10: 27.1 mg/kg soil dw  Key study, K1, used for PNEC

ECHA has requested three soil studies for OTNE in their final decision (May 2015, Decision number: CCH-D-2114297145-44-01/F) and were conducted the year after (2016) The results are presented above. The PNEC soil is 2.7 mg/kg soil dw.

It is discussed below that the EP method presents sufficiently conservative results in comparison with the experimental terrestrial toxicity information. The lowest experimental EC10 value is based on the plant tests: 27 mg/kg soil dw. The PNEC soil based on experimental testing results in 2.7 mg/kg soil dw, using an assessment factor of 10.

Additional information

Discussion on the PNEC soil EP method versus aquatic toxicity: Before discussing the PNEC first the actual values will be predicted. The EP method presents a value of 70 mg/kg soil dw based on the lowest aquatic long-term invertebrate value. Comparing this aquatic derived soil value with the experimental soil invertebrates NOEC soil, which is 31.6 mg/kg dw soil it can be seen that these values are very similar and that the EP method seems to predict the soil toxicity well. Using the EP method an additional factor of 10 is used for substances with log Kow =>5 to take into account higher availability of the substance via the gastro-intestinal tract when the substance is highly absorbing to soil (the digestion may result in higher bioavailability).

The EP method derived soil PNEC results in 7 mg/kg soil dw, taking into account the factor 10 for PNEC derivation, but not yet the additional factor of 10 for substances with Log Kow =>5. The PNEC experimental result in 2.7 mg/kg soil dw. This shows that the PNEC soil is similar using both methods without the factor 10 for ingestion.

Discussion on PNEC soil versus PNEC sediment:

The second line of evidence results from the long-term sediment toxicity test. The information from the long-term sediment toxicity studies on three types of species result in the lowest NOEC of 14.9 (converted to 2% organic carbon in soil) and the resulting PNECsoil from this set would be 1.49 mg/kg dw. An additional factor of 10, for other than pore water exposures, is not needed because the sediment organism presented will be exposed to all routes of exposures (pore water and gastro-intestinal tract). 

Overall summary: PNEC soil from experimental soil studies is 2.7 mg/kg dw and this is very similar to the PNEC from aquatic studies using the EP method, 7 mg/kg soil dw, without the additional factor of 10 for exposure via the gastro-intestinal tract.