Registration Dossier

Administrative data

Description of key information

The key studies for skin and eye irritation were read across from the structurally analogous substance octamethylcyclotetrasiloxane (CAS 556-67-2). The key study for skin irritation reports no irritation to the skin of rabbits.  The study was pre-GLP but equivalent to OECD TG 404 (Bluestar 1971).   The key study for eye irritation reports no irritant effects in rabbit eye, as reported in a reliable, pre-GLP study (Bayer 1979).  

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

For the registration substance, the key studies for skin and eye irritation were read across from the structurally analogous substance octamethylcyclotetrasiloxane (CAS 556-67-2).

The key study for skin irritation was conducted according to a study protocol comparable to the appropriate OECD test guideline but it was not compliant with GLP. 0.5 ml undiluted test substance was applied to intact and abraded skin of rabbits, for 24 hours (type of coverage not reported). No irritant effects were reported (Bluestar 1971).

The key study for eye irritation was conducted according to a study protocol comparable to the appropriate OECD test guideline, but it was not compliant with GLP. A single instillation of 0.1 ml test material was applied into the rabbit eye, with no thereafter rinsing. No eye irritation was observed. Only 2 animals were used, with no effects seen in either of the test animals (Bayer 1979).

Read-across justification

2,4,6,8-Tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (Vi4-D4) belongs to the structural class of siloxanes (alkyl, vinyl, aryl or hydrogen substituted). The substances all have high log Kow and low water solubility. In vivo skin and eye irritation studies are available for a number of these substances. For the registration substance itself, no data are available therefore read-across from the next nearest member of the group is used (D4, octamethylcyclotetrasiloxane).

The available studies for the linear siloxanes from this analogue group are summarised in the table below. The results of the irritation studies for this analogue group are in agreement: there is no evidence from any of the available studies that the substances in this group have any potential for skin or eye irritation.

Furthermore, data for related alkoxysilane substances (which share common hydrolysis products with the cyclic siloxanes) show that the presence of a vinyl group in place of a saturated alkyl group does not cause any enhanced irritation effect. Full details of the available data for the alkyl alkoxysilanes is given in a supporting report attached in Section 13 (PFA, 2013t).

It is therefore valid to read-across the lack of irritation between the members of the group where there are data gaps.

Skin and eye irritation studies for cyclic siloxanes

CAS Number

Name

Synonym

log Kow

Skin irritation

Eye irritation

556-67-2

Octamethylcyclotetrasiloxane

D4

6.5

Not irritant

(Pasquet, 1971)

Not irritant

(Bayer, 1979)

2554-06-5

2,4,6,8-Tetramethyl-2,4,6,8-tetramethylcyclotetrasiloxane

Vi4-D4

6.5

-

-

541-02-6

Decamethylcyclopentasiloxane

D5

8.0

Not irritant

(Toxikon, 1990b)

Not irritant

(Toxikon, 1990c)

2370-88-9 & 6166-86-5

Mixture of 2,4,6,8-Tetramethyl-2,4,6,8-tetramethylcyclotetrasiloxane and 2,4,6,8,10-pentamethylcyclopentasiloxane

HD4 & HD5

5.5-6.5

Not irritant

(Dow Corning Corporation, 2001)

Not irritant

(Dow Corning Corporation, 2002b)

540-97-6

Dodecamethylcyclohexasiloxane

D6

8.9

Not irritant

(Notox, 1999c)

Not irritant

(Notox, 1999d)



Justification for classification or non-classification

Based on the available information read across from the structurally analogous substance octamethylcyclotetrasiloxane (CAS 556-67-2), 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane is not classified for skin or eye irritation according to Regulation (EC) No 1272/2008.