Polysulfides, bis[3-(triethoxysilyl)propyl]

Sediment toxicity

Link to relevant study record(s)

Reference

Endpoint:

sediment toxicity: long-term

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

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Additional information

In accordance with Column 2 of REACH Annex X, long-term toxicity testing with sediment organisms (required in Section 9.5.1 of REACH Annex X) is not needed as the chemical safety assessment according to Annex I indicates that this is not necessary. - Due to the moderate rate of hydrolysis of the substance, the chemical safely assessment is based on both the parent substance, bis[3-(triethoxysilyl)propyl]polysulfides (CAS 211519-85-6, EC 915-673-4), and the silanol hydrolysis products, (3-{[3-(trihydroxysilyl)propyl]disulfanyl}propyl)silanetriol, (3-{[3-(trihydroxysilyl)propyl]trisulfanyl}propyl)silanetriol and [3-({[3-(trihydroxysilyl)propyl]disulfanyl}disulfanyl)propyl]silanetriol.

 

Parent: Bis[3-(triethoxysilyl)propyl]polysulfides: Testing for toxicity to sediment dwelling organisms is not considered necessary because: PNECsediment has been calculated from the aquatic data using the Equilibrium Partitioning Method. The risk characterisation ratios (RCR) based on the PNECsediment are <1. In accordance with Column 2 of REACH Annex X, there is no need to further investigate the effects of this substance in a sediment toxicity study because, as indicated in guidance R.7.11.6 (ECHA 2017), the quantitative chemical safety assessment (conducted according to Annex I of REACH) indicates that the Risk Characterisation Ratio (RCR) is well below 1, even with due consideration of contributing uncertainties, and therefore the risk is already adequately controlled and further testing is not justifiable. The substance is not readily biodegradable, is not bioaccumulative (based on BCF = ≤ 188 to 511 (mean: 244, see IUCLID Section 5.3 for further details)), but has some potential for adsorption (based on log K_oc 3.1); therefore, bis[3-(triethoxysilyl)propyl]polysulfides is expected to partly partition to the sediment compartment. No toxicity of bis[3-(triethoxysilyl)propyl]polysulfides was observed in aquatic tests at or below the limit of solubility (0.01 mg/l at 20°C). There is no reason to expect any specific mechanism of toxicity beyond narcosis. Therefore, the occurrence of more severe toxic effects in the sediment compartment that were not expressed in the aquatic studies would be considered unlikely. Overall, it is concluded that the risk characterisation conclusion is sufficiently conservative in respect of any uncertainties and therefore further testing is not considered necessary. Details on how the PNEC and the risk characterisation ratio have been derived can be found in IUCLID Section 6.0 and Chapters 9 and 10 of the Chemical Safety Report, respectively.

 

Silanol hydrolysis products: (3-{[3-(trihydroxysilyl)propyl]disulfanyl}propyl)silanetriol, (3-{[3-(trihydroxysilyl)propyl]trisulfanyl}propyl)silanetriol and [3-({[3-(trihydroxysilyl)propyl]disulfanyl}disulfanyl)propyl]silanetriol: Testing for toxicity to sediment dwelling organisms is not considered necessary because: PNECsediment has been calculated from the aquatic data using the Equilibrium Partitioning Method. The risk characterisation ratios (RCR) based on the PNECsediment are <1. In accordance with Column 2 of REACH Annex X, there is no need to further investigate the effects of this substance in a sediment toxicity study because, as indicated in guidance R.7.11.6 (ECHA 2017), the quantitative chemical safety assessment (conducted according to Annex I of REACH) indicates that the Risk Characterisation Ratio (RCR) is well below 1, even with due consideration of contributing uncertainties, and therefore the risk is already adequately controlled and further testing is not justifiable. The substance is not readily biodegradable but has low potential for bioaccumulation and a low potential for adsorption (based on log K_ow <3 (-3.0) and log K_oc -3.2); therefore, partitioning to the sediment compartment is expected to be minimal. Some toxicity of the silanol hydrolysis products was observed in aquatic tests below the limit of solubility (1.0E+06 mg/l), as the algal EL₅₀value is 700 mg/l. However, this value is above the concentration at which water solubility will be limited by condensation reactions (100 mg/l). There is no reason to expect any specific mechanism of toxicity beyond narcosis. Therefore, the occurrence of more severe toxic effects in the sediment compartment that were not expressed in the aquatic studies would be considered unlikely. Overall, it is concluded that the risk characterisation conclusion is sufficiently conservative in respect of any uncertainties and therefore further testing is not considered necessary. Details on how the PNEC and the risk characterisation ratio have been derived can be found in IUCLID Section 6.0 and Chapters 9 and 10 of the Chemical Safety Report, respectively.