Registration Dossier

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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Administrative data

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:
no hazard identified

Marine water

Hazard assessment conclusion:
no hazard identified

STP

Hazard assessment conclusion:
PNEC STP
PNEC value:
0.92 mg/L
Assessment factor:
100
Extrapolation method:
assessment factor

Sediment (freshwater)

Hazard assessment conclusion:
PNEC sediment (freshwater)
PNEC value:
0.68 mg/kg sediment dw
Extrapolation method:
equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:
PNEC sediment (marine water)
PNEC value:
0.068 mg/kg sediment dw
Extrapolation method:
equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:
no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:
PNEC soil
PNEC value:
0.14 mg/kg soil dw
Extrapolation method:
equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:
PNEC oral
PNEC value:
3.33 mg/kg food
Assessment factor:
300

Additional information

The hydrolysis half-life of [2-(perfluorohexyl)ethyl]dichloro(methyl)silane (CAS 73609-36-6) is <1 minute at pH 7, 20-25⁰C based on read-across data. The substance will hydrolyse in water under dilute conditions to [2-(perfluorohexyl)ethyl]methylsilanediol and hydrochloric acid. 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”. TGD and ECHA guidance (EC 2003, ECHA 2016) also suggest that when the hydrolysis half-life is less than 1 hour, the breakdown products, rather than the parent substance, should be evaluated for aquatic toxicity. Therefore, the environmental hazard assessment is based on the properties of the silanol hydrolysis product, in accordance with REACH guidance. As described in Section 4.8 of IUCLID, the silanol hydrolysis products may be susceptible to condensation reactions.

[2-(Perfluorohexyl)ethyl]methylsilanediol has very low water solubility (0.0048 mg/l), high log Kow (4.6) and low vapour pressure (0.38 Pa).

 

In order to reduce testing, read-across is proposed to fulfil up to REACH Annex VIII requirements for the registration substance from substances that have similar structure and physicochemical properties. Ecotoxicological studies are conducted in aquatic medium or in moist environments; therefore the hydrolysis rate of the substance is particularly important, because after hydrolysis occurs the resulting product has different structural features, physicochemical properties and behaviour.  

The registration substance and the substance used as surrogate for read-across are part of a class of low-functionality compounds acting via a non-polar narcosis mechanism of toxicity. The group of organosilicon substances in this group contain alkyl, aryl, alkoxy or hydroxy groups attached to the silicon atom when present in aqueous solution. Secondary features may be present in the alkyl chain (e.g. halogen, nitrile, unsaturated bonds) that do not affect the toxicity of the substances (additional information is given in a supporting report (PFA, 2016y) attached in Section 13). The silanol hydrolysis products may be susceptible to condensation reactions, see Section 4.8.  

The analogue approach for fulfilling the data requirement by read-across is discussed in the RAAF report for ecotoxicity attached in Section 13 of IUCLID, according to the Read-across Assessment Framework (RAAF).

References:

EC 2003:European Union Technical Guidance Document on Risk Assessment for New and Existing Substances, Part II, European Chemicals Bureau, 2003.

ECHA 2016: European Chemicals Agency. Guidance on information requirements and chemical safety assessment Chapter R.16: Environmental Exposure Estimation. Version: 3.0, February 2016.

Horvath, A.L. (1982) Halogenated Hydrocarbons. Solubility-Miscibility with Water, Marcel Dekker, New York, 1982.

OECD SIDS (2002) SIDS Initial Assessment Report for SIAM 15, Boston, USA, 22-25th October 2002, Hydrochloric acid, CAS 7647-01-0.

OECD (2004b): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 19-22 October 2004, Ethanol, CAS 64-17-5.

PFA, 2016y, Peter Fisk Associates, Analogue Report - Ecotoxicity of substances with ‘low-functionality’ side chains attached to silicon, PFA. 404.003.004.R1

Conclusion on classification

The substance has reliable short-term E(L)C50 values of >3.1 mg/l (greater than the limit of solubility) in fish, >9 mg/l (greater than the limit of solubility in water) in invertebrates and >7.1 mg/l (greater than the limit of solubility in water) in algae, as well as a reliable NOEC of ≥7.1 mg/l (greater than the limit of solubility) in algae, based on read-across data from the structural analogue [2-(perfluorohexyl)ethyl]triethoxysilane (CAS 51851-37-7). The available aquatic toxicity data indicate that there are no effects on aquatic organisms at the limit of solubility of the substance in water.

The registration substance hydrolyses rapidly to [2-(perfluorohexyl)ethyl]methylsilanediol, which is not readily biodegradable, based on read-across data, and is poorly water soluble, which could mean it is likely to persist in the environment. The log Kow is >4 (4.6) and so the 'safety net' criteria for classification applies.

These data are consistent with the following classification under Regulation (EC) No 1272/2008 (as amended) (CLP):

Acute toxicity: Not classified.

Chronic toxicity: Category Chronic 4