Triethoxy(3-thiocyanatopropyl)silane

Endpoint summary

Additional information

Approach to the Terrestrial Chemical Safety Assessment

 

The registered substance, triethoxy(3-thiocyanatopropyl)silane (CAS 34708-08-2, EC 252-161-3), will hydrolyse moderately rapidly (half-life 23 hours at pH 7 at 25°C) in contact with water and atmospheric moisture to (3-thiocyanatopropyl)silanetriol and ethanol. REACH guidance (ECHA 2016, R.16) states that “for substances where hydrolytic DT₅₀ is less than 12 hours, environmental effects are likely to be attributed to the hydrolysis product rather than to the parent itself”. ECHA Guidance Chapter R.7b (ECHA, 2017) states that where degradation rates fall between >1 hour and <72 hours, testing of parent and/or degradation product(s) should be considered on a case-by-case basis. Therefore, in accordance with REACH guidance, the terrestrial chemical safety assessment for triethoxy(3-thiocyanatopropyl)silane is based on both the registration substance and its silanol product, (3-thiocyanatopropyl)silanetriol. The non-silanol hydrolysis product, ethanol, is not expected to contribute to toxicity to terrestrial organisms. 

 

Triethoxy(3-thiocyanatopropyl)silane is classed as hazard category 3 for the terrestrial environment (Table R.7.11-2 of ECHA guidance R7.c, 2017) based on potential for high persistence (DT₅₀ > 180 days), lack of ready biodegradability and low toxicity to aquatic organisms (EC/LC₅₀ not <1 mg/l).

In this situation, a screening approach is applied: a confirmatory long-term terrestrial test is conducted, in addition to the equilibrium partitioning approach with an extra factor of ten in order to determine whether further full tests are necessary.

There are ongoing long-term aquatic studies conducted according to OECD TG 211 and 210 for aquatic invertebrates and fish, respectively. There are also ongoing long-term terrestrial toxicity studies conducted according to OECD TG 216 and 222 for soil microorganisms and soil macrorganisms except arthropods, respectively. An OECD TG 208 terrestrial plant toxicity study is also required by ECHA final decision number TPE-D-2119966910-31-01/F. However, the studies are being carried out in a tiered manner with the OECD 210, 211, 216 and 222 studies being conducted first.

Once the results from these studies become available, the PNEC_soil will be updated, a new environmental exposure assessment will be conducted and the need for further terrestrial testing with terrestrial plants will be evaluated based on the updated agricultural soil RCRs and observations of toxicity in the OECD 222 study.

Until the results from these studies become available, the PNECsoil and risk characterisation ratio have been derived based on the equilibrium partitioning method, details of which can be found in IUCLID Section 6 and Chapters 9 and 10 of the Chemical Safety Report, respectively.