Registration Dossier
Registration Dossier
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EC number: 209-136-7 | CAS number: 556-67-2
Toxicity to soil macroorganisms except arthropods
Administrative data
Link to relevant study record(s)
Description of key information
Long-term toxicity to soil macroorganisms except arthropods:
28-day EC50 >130 mg/kg dw (mean measured concentration), survival and weight of Eisenia fetida;
28-day NOEC ≥130 mg/kg dw (mean measured concentration), survival and weight of Eisenia fetida;
56-day NOEC 75 mg/kg dw (mean measured concentration), reproduction of Eisenia fetida, normalised to 2% organic carbon = NOEC 42 mg/kg dw.
Key value for chemical safety assessment
- Long-term EC10, LC10 or NOEC for soil macroorganisms:
- 42 mg/kg soil dw
Additional information
A long-term toxicity to soil macroorganisms except arthropods study according to the OECD test guideline 222 and in compliance with GLP has been conducted with the registered substance (Smithers 2022), according to ECHA final decision TPE-D-2114422498-44-01/F.
The study reports the following effects on earthworm survival, growth and reproduction:
• 28-day NOEC value for adult Eisenia fetida survival and weight: ≥130 mg/kg dry substrate based on mean measured concentration (≥1000 mg/kg dw nominal concentration).
• 28-day LOEC value for adult Eisenia fetida survival and weight: >130 mg/kg dry substrate based on mean measured concentration (>1000 mg/kg dw nominal concentration).
• 28-day LC50 value for adult Eisenia fetida survival and weight: >130 mg/kg dry substrate based on mean measured concentration (>1000 mg/kg dw nominal concentration).
• NOEC value based on reproduction: 75 mg/kg dry substrate based on mean measured concentration (500 mg/kg dw nominal concentration).
• LOEC value based on reproduction: 130 mg/kg dry substrate based on mean measured concentration (1000 mg/kg dw nominal concentration).
• EC50 value for effects on reproduction: >130 mg/kg dry substrate based on mean measured concentration (>1000 mg/kg dw nominal concentration).
Effect concentration values have been reported in terms of mean measured concentrations because significant test substance losses occurred and concentrations were not maintained within 80% of nominal concentrations. This is consistent with the findings of the preliminary stability trial (reported below).
The NOEC for reproduction based on measured concentrations is equivalent to 42 mg/kg dwt when normalised to 2% organic carbon content.
Due to the potential volatility of the registration substance, a stability trial under OECD 222 conditions was carried out prior to the definitive study.
The stability assessment was executed over a 56 day period using [14C] radiolabelled octamethylcyclotetrasiloxane (D4, CAS 556-67-2, EC No. 209-136-7) test substance. The trial was carried out under OECD 222 test conditions, in natural soil, but without test organisms.
The radiolabelled test substance was mixed into natural soil to prepare a nominal concentration of 1000 mg/kg. Chemical analysis was performed by taking triplicate soil cores from one of the treated replicates at Days 0, 3, 7, 14, 28, and 56 and analysed by liquid scintillation counting (LSC) and high-performance liquid chromatography with radiometric detection (HPLC-RAM).
The measured applied test concentration was 117 mg/kg dry weight soil.
The test substance was determined to be not stable in natural soil. This was based on the material balance decreasing from 107 to 35.4% applied radioactivity (% AR) on Day 0 and 56, respectively, and average [14C]D4 decreasing from 92.3 to 11.4% AR on Day 0 and 56, respectively.
Further details are reported in the stability assessment EPSR (Smithers, 2020a).
This definitive earthworm study was severely delayed due to difficulties with survival of earthworm populations. Prior to this exposure, an initial definitive limit test exposure was conducted at Smithers from January to March 2020. As there was a 29% effect at the limit test concentration (1000 mg/kg), it did not qualify as a limit test. A second definitive exposure was conducted at Smithers from August to October 2020 with five concentrations (63, 130, 250, 500, and 1000 mg/kg). The exposure was not reported due to not meeting acceptance criteria for juvenile production per replicate in the control. A third definitive exposure was conducted at Smithers from December to February 2021 with five concentrations (63, 130, 250, 500, and 1000 mg/kg). The exposure was not reported due to overall poor adult worm survival resulting in failure to meet control adult survival criterion. An additional trial was conducted to identify organism survival issues and once complete, the exposure was reset using the best methods determined from the trial (i.e., using earthworms hatched in an in-house culture and using a different natural soil source).
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