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Description of key information

In the first key in vitro skin irritation study with octaphenylcyclotetrasiloxane (CAS 546-56-5) using EpiDermTM tissue, the reported mean relative tissue viability (% negative control) was > 50 % (91.4 %) after 60 minutes treatment and 42 hours post-incubation (Eurofins, 2017).

In the second key in vitro skin irritation study with octaphenylcyclotetrasiloxane (CAS 546-56-5) using EpiSkinTM tissue, the reported mean relative tissue viability (% negative control) was > 50 % (104.9 %) after 15 minutes treatment and 42 hours post-incubation (Eurofins, 2017a).

In the key in vitro Bovine Corneal Opacity and Permeability Assay, conducted according to an appropriate OECD test guideline and in compliance with GLP, the in vitro irritation score reported for the test substance, octaphenylcyclotetrasiloxane, was < 3. The test substance was concluded to be not irritating to eyes (Eurofins, 2017).  

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 potential of octaphenylcyclotetrasiloxane (CAS 546-56-5) to induce skin irritation was analysed by using a three-dimensional human epidermis model EpiDermä(MatTek) comprising a reconstructed epidermis with a functional stratum corneum (Eurofins, 2017).

The test substance was applied topically to the EpiDermä tissue for 60 min followed by a 42 h post-incubation period and immediate determination of cytotoxic effects via MTT reduction assay. Irritant potential of the test item was predicted from the relative mean tissue viabilities obtained compared to the corresponding negative control tissues concurrently treated with DPBS.

The test item showed no non-specific reduction of MTT and no colouring after mixture with aqua dest. and isopropanol. Therefore, no additional controls were necessary. The test item showed no irritant effects. The mean relative tissue viability (% negative control) was> 50% (91.4%) after 60 min treatment and 42 h post-incubation. The controls confirmed the validity of the study.

The potential of octaphenylcyclotetrasiloxane (CAS 546-56-5) to induce skin irritation was also analysed by using the three-dimensional human skin model EPISKIN-SM comprising a reconstructed epidermis with a functional stratum corneum (Eurofins, 2017a). The test substance was applied topically to the EPISKIN-SM for 15 min followed by a 42 h post-incubation period and immediate determination of cytotoxic effects via MTT reduction assay.

Irritant potential of the test item was predicted from the relative mean tissue viabilities obtained compared to the corresponding negative control tissues concurrently treated with DPBS.

The test item showed no non-specific MTT reducing potential and no colouring potential, therefore no additional controls for correction of results were necessary. The test item showed no irritant effects. The mean relative tissue viability (% negative control) was> 50% (104.9%) after 15 min treatment and 42 h post-incubation. The controls confirmed the validity of the study.

The eye irritancy potential of octaphenylcyclotetrasiloxane (CAS 546-56-5) was investigated in the bovine corneal opacity and permeability assay. The test item was suspended with corn oil to give a 20% concentration. 750 µL of the test item preparation or the control substance was introduced into the anterior chamber (closed-chamber method). After 4 hours ± 5 minutes incubation at 32 ± 1 °C either the test substance or the control substance was removed and the epithelium washed at least three times with MEM. Once the medium was free of test substance, the cornea was finally rinsed with complete RPMI (without phenol red). The anterior chamber was refilled with complete RPMI and an illuminance measurement was performed. Also, each cornea was observed visually and pertinent observations were recorded. Then the corneas were incubated for 90 minutes at 32±1 °C. Then the medium from the posterior chamber was removed and its optical density at 490 nm (OD490) was determined, using a spectrophotometer.

The calculated in vitro irritation score was calculated to be 1.55. The in vitro irritation score obtained with the positive control fell within the two standard deviations of the current historical mean and therefore this assay is considered to be valid. The negative control responses should result in opacity and permeability values that are less than the established upper limits for background bovine corneas treated with the respective negative control.

Justification for classification or non-classification

Based on the available data for octaphenylcyclotetrasiloxane (CAS 546-56-5), no classification for skin and eye irritation is required according to Regulation (EC) No 1272/2008.