Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

A category approach is applied to this endpoint and is detailed in the Siloxane Category report (PFA, 2017). There is a limited amount of terrestrial toxicity data available with siloxanes. An integrated testing strategy for the category is proposed. In view of the high potential to adsorb to soil for siloxane substances, and the lack of terrestrial toxicity testing across the Category, it is concluded that further testing is required.

Screening Assessment and Testing Strategy for ViM4Q

The registration substance falls within soil hazard category 3 as defined in REACH R.7; high absorption (log Kow >5) but no indication that the substance is very toxic to aquatic organisms. Aquatic toxicity data show no effects at concentrations that are close to or above the limit of water solubility of the substance. As discussed in IUCLID Section 6 and CSR Section 7.1.2.1, a true PNECaquatic cannot be calculated from the test data because the LC50/EC50 and NOEC values that have been determined are limit values. However, in order to conduct the screening assessment for terrestrial testing, an indicative PNECaqua is derived solely for this purpose. Short-term aquatic data only are available. An assessment factor of 1000 is applicable to the lowest limit E(L)C50 value of >14.2 ng/l derived in the short-term tests.

A PNECaqua(freshwater) value of >1.42E-08 mg/l can be used to calculate a PNECsoil(screening) using the equilibrium partitioning approach.

PNECsoil = Ksoil-water/RHOsoil * PNECaquatic(freshwater) * 1000

For ViM4Q this is:

PNECsoil(screening) = 4630/1700 * >1.42E-08 * 1000 = >3.87E-05 mg/kg wwt

This is equivalent to >0.000044 mg/kg dwt.

In order to complete the screening assessment, a confirmatory long-term soil toxicity test is required.

Terrestrial toxicity studies with siloxanes are considered to be difficult to conduct due to their high volatilisation potential (high Henry’s Law Constant and low octanol-air partition coefficient) and the potential for degradation in soil. This is based both on chemical properties, and challenges encountered in studies of fate and ecotoxicity conducted to date with substances within this Category. Soil testing according to guideline methods does not allow for a renewal of the substrate and hence re-application of test substance. Therefore, there is potential for the organisms to not be exposed to the test material for a sufficiently long period of time for effects to be expressed, as well as the difficulty of quantifying actual exposure concentrations.

A stability/recovery test under OECD TG 222 conditions has been performed with the registered substance. ViM4Q was determined to be stable in natural soil. This was based on analytical recoveries for the 1000 mg/kg treatment level of between 102 and 105% at day 28.

The definitive OECD TG 222 study will therefore be conducted in accordance with ECHA final decision TPE-D-2114422682-53-01/F.

The need for further terrestrial toxicity tests (OECD TG 208) will be reviewed once the results of this study are available.

An OECD TG 216 toxicity to soil microorganisms study is also being conducted with the registration substance in accordance with ECHA final decision TPE-D-2114422682-53-01/F.

The substance dossier and risk assessment will be updated once results of the studies are available and the studies are finalised. Final reports are expected in February 2021 for the OECD 222 study and October 2020 for the OECD 216 study. Please see a letter from the testing laboratory, attached in IUCLID Section 6.3.1 and 6.3.4 placeholder EPSRs, for further details.

Until these data become available, PNECsoil has been derived based on data read across from decamethylcyclopentasiloxane (D5, CAS 541-02-6) in order to perform risk characterisation..

Terrestrial toxicity data are read-across from decamethylcyclopentasiloxane (D5, CAS: 541-02-6), a siloxane with similar physico-chemical properties to the registered substance. The data are considered to be suitable for deriving an interim PNECsoil for the registered substance. The testing has been carried out with species that are representative of three taxonomic groups; earthworms, springtails and plants.

· A 28 day LC50 value of >4074 mg/kg dry weight and a 56 day NOEC of ≥4074 mg/kg dry weight have been determined for the effects of the test substance on mortality and reproduction and growth respectively of the earthworm, Eisenia andrei.

· A 28 day LC50 value of 813 mg/kg dry weight and a 28 day IC50 value of 767 mg/kg dry weight have been determined for the effects of the test substance on mortality and reproduction of the springtail, Folsomia candida. A NOEC of 377 mg/kg dry weight has been determined by the reviewer on the basis of a visual examination of the data for both mortality and reproduction.

· A 14 day IC50 value of 209 mg/kg dry weight has been determined for the effects of the test substance on root dry mass of Barley, Hordeum vulgare. IC50/EC50 values for effects on seedling emergence, root and shoot length and shoot dry mass determined in the same test were ≥248 mg/kg dry weight. 14 Day EC50 values of >4054 mg/kg dry weight have been determined for the effects of the test substance on seedling emergence, root and shoot length and root and shoot dry mass of Red Clover, Trifolium pratense. NOECs were not determined in the tests.

The studies are considered to be non-standard; they have been conducted by spiking surrogate biosolids mixed into natural soil rather than by direct spiking of soil. The registered substance and the surrogate substance share similar physico-chemical properties but are not close structural analogues (linear and cyclic siloxanes).

Read-across of the terrestrial toxicity data for D5 to ViM4Q is considered to be suitable to derive an interim hazard and risk assessment under REACH until the results of the studies with ViM4Q are available.