Registration Dossier

Administrative data

Description of key information

A mixture of the two structurally analogous substances 2,4,6,8,10-pentamethylcyclopentasiloxane (CAS 6166-86-5) and 2,4,6,8-tetramethylcyclotetrasiloxane (CAS 2370 -99 -0) was tested for skin irritancy according to OECD 404 test method under GLP . No signs of skin irritation were observed.

The mixture of structurally analogous substances 2,4,6,8,10-pentamethylcyclopentasiloxane (CAS 6166-86-5) and 2,4,6,8-tetramethylcyclotetrasiloxane (CAS 2370-99-0) was tested in an in vivo eye irritation test according to OECD 405 under GLP. The mixture produced minimal conjunctival redness at 4, 24 and 48 h and minimal chemosis at 4 h, all fully reversible and the mixture was concluded to be not irritating to eyes.

Both studies were done with mixture (approximately 50/50) of the structural analogues 2,4,6,8,10-pentamethylcyclopentasiloxane (CAS 6166-86-5) and 2,4,6,8-tetramethylcyclotetrasiloxane (CAS 2370-88-9).

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

Skin:

A mixture of the two structurally analogous substances 2,4,6,8,10-pentamethylcyclopentasiloxane (CAS 6166-86-5) and 2,4,6,8-tetramethylcyclotetrasiloxane (CAS 2370 -99 -0) was tested for skin irritancy according to OECD 404 test method under GLP . No signs of skin irritation were observed. Based on structural analogy, the conclusion applies directly to the registered substance as well as from read-across from the analogue.

Eyes:

The mixture of structurally analogous substances 2,4,6,8,10-pentamethylcyclopentasiloxane (CAS 6166-86-5) and 2,4,6,8-tetramethylcyclotetrasiloxane (CAS 2370-99-0) was tested in an in vivo eye irritation test according to OECD 405 under GLP. The mixture produced minimal conjunctival redness at 4, 24 and 48 h and minimal chemosis at 4 h, all fully reversible. The conclusion applies directly to the registered substance as well as indirectly by read-across from the structural analogue which is also present in the mixture.

Read-across justification

Read-across to the submission substance is justified because: (i) the test substance includes ca.50% by weight of the submission substance, and (ii) the second component is a close structural analogue of the submission substance.

Also, HD5 is one of a number of cyclic siloxanes containing no functional groups for which skin and eye irritation data are available. The results of all available studies, summarised in Table 5.3.3, are in agreement and show that none of the substances in this analogue group is irritating to either skin or eyes

Table5.3.3Skin and eye irritation studies for cyclic siloxanes

CAS Number

556-67-2

541-02-6

540-97-6

Mixture of 2370-88-9 and 6166-86-5

Name

Octamethylcyclotetrasiloxane

Decamethylcyclopentasiloxane

Dodecamethylcyclohexasiloxane

 

Synonym

D4

D5

D6

HD4/HD5

Skin irritation

Not irritant

(Pasquet, 1971)

Not irritant

(Toxikon, 1990b)

Not irritant

(Notox, 1999c)

Not irritant

(Dow Corning Corporation, 2001)

Eye irritation

Not irritant

(Bayer, 1979)

Not irritant

(Toxikon, 1990c)

Not irritant

(Notox, 1999d)

Not irritant

(Dow Corning Corporation, 2002b)



Justification for classification or non-classification

Based on the available data for the mixture (approximately 50/50) of the structural analogues 2,4,6,8,10-pentamethylcyclopentasiloxane (CAS 6166-86-5) and 2,4,6,8-tetramethylcyclotetrasiloxane (CAS 2370-88-9), no classification is required for skin and eye irritation for the registered substance 2,4,6,8,10-pentamethylcyclopentasiloxane (CAS 6166-86-5) according to Regulation (EC) No 1272/2008.