Registration Dossier

Administrative data

Description of key information

The key study for skin irritation is read across from structurally analogous substance dodecamethylpentasiloxane (CAS 141-63-9). The study, conducted according to OECD TG 404 and in compliance with GLP, reports the test substance, dodecamethylpentasiloxane (CAS 141-63-9), to be not irritating to skin (Dow Corning Corporation, 2009). The key study for eye irritation is read across from structurally analogous substance decamethyltetrasiloxane (CAS 141-62-8). The study, conducted according to EPA OPPTS 870.2400 (Acute Eye Irritation) guideline, and in compliance with GLP, reports the test material, decamethyltetrasiloxane (CAS 141-62-8), to be not irritating to the eyes (Dow Corning Corporation, 2000).

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

The key study for skin irritation is read across from structurally analogous substance dodecamethylpentasiloxane (CAS 141-63-9). The study, conducted according to OECD TG 404 and in compliance with GLP, reports the test substance, dodecamethylpentasiloxane (CAS 141-63-9), to be not irritating to skin (Dow Corning Corporation, 2009).

Following a 4 -hour application of 0.5 ml of undiluted test material onto the skin of 3 rabbits, no signs of dermal irritation, erythema or oedema were seen at any scoring interval (24, 48 and 72 hours) throughout the study on any animal. There were also no notable lesions or any additional dermal findings noted during experimental phase.

The key study for eye irritation is read across from structurally analogous substance decamethyltetrasiloxane (CAS 141-62-8). The study, conducted according to EPA OPPTS 870.2400 (Acute Eye Irritation) guideline, and in compliance with GLP, reports the test material, decamethyltetrasiloxane (CAS 141-62-8), to be not irritating to the eyes (Dow Corning Corporation, 2000).

Following a single instillation of 0.1 ml of the test material, into the eyes of three rabbits, transient hyperaemia of the blood vessels of the conjunctivae in two animals was observed. Ocular reactions had resolved completely in both animals by one day after instillation. There were no signs of irritation in the third animal. No deaths occurred during the study. No clinical signs of systemic reaction to treatment were observed.

READ-ACROSS JUSTIFICATION

To reduce animal testing REACH recommends to make use of a read-across approach where appropriate based on the high accordance in properties relevant for the specific endpoint. In the case of irritation relevant properties are structural similarity, hydrolysis rate and the physical-chemical parameters in the same range. In the following paragraphs the proposed read-across is discussed.

Further information can be found in the supporting report (PFA, 2013u) attached in Section 13 of the IUCLID 6 dossier. 

Read-across hypothesis

The hypothesis is that the target (registered) source substance and the (read-across) substances have similar toxicological properties because they are linear siloxanes with similar physicochemical properties and are structurally similar with similar hydrolysis rates so have similar toxicological properties.

Read-across justification

a) Structural similarity

Tetradecamethylhexasiloxane (L6) is a methyl-substituted linear siloxane, with six silicon atoms connected by five oxygen atoms, in which the Si-O bonds are susceptible to hydrolysis. Dodecamethylpentasiloxane (L5) and decamethyltetrasiloxane are also methyl substituted linear siloxanes, with five or four silicon atoms and four or three oxygen atoms.

b) Similar physicochemical properties

The linear siloxanes all have high log Kow (increasing with increasing chain length) and low water solubility.

c) Similar hydrolysis rates

The linear siloxanes all hydrolyse slowly at neutral pH.

Summary of key irritation data for linear siloxanes

Substance

L2

L3

L4

L5

Chemical name

Hexamethyl

disiloxane

Octamethyl

trisiloxane

Decamethyl

tetrasiloxane

Dodecamethyl

pentasiloxane

CAS number

107-46-0

107-51-7

141-62-8

141-63-9

Water solubility (mg/l)

0.93

0.034

6.7E-03

7.5E-05

Log Kow

5.1

6.6

8.1

9.4

Skin irritation result

Not irritant (Dow Corning Corporation, 1996)

Not irritant (Dow Corning Corporation, 1999)

Not irritant (Dow Corning Corporation, 2009e)

Not irritant (Dow Corning Corporation, 2009b)

Eye irritation result

Not irritant (Stauffer, 1973)

-

Not irritant (Dow Corning Corporation, 2000)

-

Reference

PFA, 2013u, Peter Fisk Associates, Analogue report - mammalian toxicity of linear and branched siloxanes, PFA.300.002.008


Justification for classification or non-classification

Based on the available information from the read across substances, dodecamethylpentasiloxane (CAS 141-63-9) and decamethyltetrasiloxane (CAS 141-62-8), no classification for skin or eye irritation/corrosion is required for the registered substance according to Regulation (EC) No 1272/2008.