Registration Dossier
Registration Dossier
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EC number: 242-472-2 | CAS number: 18643-08-8
Endpoint summary
Administrative data
Description of key information
Additional information
Chloro(dimethyl)octadecylsilane (CAS 18643-08-8) hydrolyses rapidly (<2 min) in water and humid environments to the corresponding hydrolysis products octadecyldimethylsilanol and HCl. REACH guidance R.16 states that “for substances where hydrolytic DT50 is less than 12 h, environmental effects are likely to be attributed to the hydrolysis product rather than to the parent itself” (ECHA, 2016). TGD (EC, 2003) and REACH guidance R.16 (ECHA, 2016) also suggest that when the hydrolysis half-life is less than 12 h, the breakdown products, rather than the parent substance, should be evaluated for aquatic toxicity testing.
Experimental data on the short term toxicity of chloro(dimethyl)octadecylsilane (CAS 18643-08-8) to aquatic invertebrates is available. The available study was conducted according to OECD guideline 202 and GLP criteria. The testing of the short term toxicity of the substance to Daphnia magna resulted in an EC50 (48 h) of > 100 mg/L (nominal).
The toxicity to algae was assessed using read across data from the structurally similar substance hexadecyl(trimethoxy)silane (CAS 16415-12-6). The substances share very similar silanol hydrolysis products (i.e. octadecyldimethylsilanol and hexadecylsilanetriol). The other hydrolysis products are HCl and methanol, respectively. Both substances are expected to hydrolyse within the timescale of an aquatic toxicity test. Further information on the read across approach can be found in the attached justification in the respective target entry and in the overall justification for grouping of substances attached in IUCLID Section 13.
The effect of the read across substance hexadecyl(trimethoxy)silane (CAS 16415-12-6) on the growth rate of the freshwater algae species Pseudokirchneriella subcapitata was assessed according to OECD guideline 201 and GLP criteria. The study was conducted with two different solvents. When methanol was used as a solvent the 72 h ErC50 and ErC10 were both ≥ 31.8 mg/L (nominal). When TBA was used as solvent the ErC50 (72 h) was > 29.5 mg/L and the ErC10 (72 h) was calculated to be 20.91 mg/L (nominal).
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