Silicic acid, lithium salt

Endpoint summary

Description of key information

Skin irritation (Draft proposal for a new OECD-Guideline, in vitro skin irritation: human skin model test, Dec. 2007): not irritating (silicic acid, lithium salt (MR: 4.8))
Skin irritation (OECD 404): not irritating (silicic acid, lithium salt (MR: 4.01), 25% solution) 
Eye irritation (OECD 405): corrosive (silicic acid, lithium salt (MR: 4.8))
Eye irritation (OECD 405): irritating (silicic acid, lithium salt (MR: 4.01), 25% solution)

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:

adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Additional information

Skin

in vitro

The skin irritation potential of silicic acid, lithium salt (Molar Ratio SiO2/Li2O: 4.8) was determined in the human skin model test according to the Draft proposal for a new OECD-Guideline, In vitro skin irritation: human skin model test (December, 2007). Three tissues of the human skin model EpiDerm^TM were each treated with approx. 25 mg of the solid test item (wetted with 25 µL DPBS-buffer). After 60 minutes incubation, tissues were rinsed and again incubated. After a total incubation time of 42 + 2 hours the cell viability was determined by measuring the enzymatic conversion of the vital dye MTT into a blue formazan salt photometrically. DPBS-buffer was used as negative control, 5% SDS-solution was used as positive control.

After treatment with the negative control, the absorbance values were within the required acceptability criterion of 1.0 < mean < 2.5 while the variation within tissues was acceptable. After the treatment with silicic acid, lithium salt, the relative absorbance values were increased to 111.5%. This value is well above the threshold for irritation potential (50%) (Paulus, 2009). Therefore, silicic acid, lithium salt (MR: 4.8) is considered not irritant in the Human Skin Model Test.

in vivo

In a GLP-Guideline study according to OECD Guideline 404 0.5 mL Klebofon (25% silicic acid, lithium salt and lithium silicate, 75% water) was applied semiocclusive to the skin of New Zealand rabbits for 4 hours (Merkel, 2005). Grading of skin reactions for erythema and oedema formation according to Draize was performed 1, 24, 48 and 72 hours after patch removal. Very slight erythema was noted in two animals one hour after patch removal. All animals were free from erythema by 48 hours. No signs for edema formation were observed at any reading time point. In conclusion, silicic acid, lithium salt (MR: 4.01) in a concentration of 25% has no skin irritation potential.

Eye

in vivo

The acute eye irritation of silicic acid, lithium salt (Molar Ratio SiO2/Li2O: 4.8) was investigated in a GLP-Guideline study according to OECD Guideline 405 in three female New Zealand rabbits (Colas, 2011). 0.1 g of the test substance was instilled into one eye after being reduced to fine powder. The other eye remained untreated serving as control. The resulting ocular reactions to silicic acid, lithium salt was evaluated until day 21 after treatment.

At the conjunctivae level a moderate to important redness were noted 1 hour after installation. This reaction was totally reversible between days 7 and 16 and associated with a strong chemosis, observed 1 hour after the installation but totally reversible between days 7 and 8. At the iris level a congestion was noted in each animal 1 hour after treatment while total reversibility occurred between days 4 and 7. Slight to moderate corneal opacity were found 1 or 24 hours after silicic acid, lithium salt installation. The corneal opacity was totally reversible in two animals on day 7 or day 16 and remained on day 21 (last day of the test) in the third animal (moderate intensity, score 2). A corneal neovascularisation was noted from day 7 or day 10 in two animals and was totally reversible on day 16 in one animal and remained until day 21 in the other one. A swelling of the cornea was noted from day 2 or day 4 and totally reversible between days 7 and 21. White secretion requiring a physiological rinse were noted in one animal on day 1 and day 2.

In conclusion, silicic acid, lithium salt (MR: 4.8) caused irreversible effects on the eye and is therefore considered as corrosive.

In another study, Klebofon (25% silicic acid, lithium salt, lithium silicate (Molar Ratio: 4.01), 75% water) was tested in GLP-Guideline study according to OECD 405 for its eye irritation/corrosion potential (Merkel, 2005). 0.1 mL of the test was instilled into the right eye of one female and two male rabbits. The left eye remained untreated and served as control. Ocular irritation was evaluated by the method of Draize. One hour after test substance instillation, all three treated eyes exhibited corneal opacity, iritis and conjunctivitis. At the conjunctival level (redness) the mean scores after 24, 48 and 72 h were 1.3, 2 and 2.3. In general, the overall incidence and severity of irritation decreased with time. All animals were free of ocular irritation by day 7 (study termination).

In conclusion, silicic acid, lithium salt (MR: 4:01) in a concentration of 25% showed irritating effects.

Effects on eye irritation: corrosive

Effects on respiratory irritation: irritating

Justification for classification or non-classification

Skin

Silicic acid, lithium salt (MR: 4.8) is considered to be not irritant based on the results of a Human Skin Model test according to the Draft proposal for a new OECD-Guideline, In vitro skin irritation: Human Skin Model test (December, 2007), since the tissue viability after 24 h exposure and post-treatment incubation (42 h) was more than 50%, i.e. after treatment the relative mean absorbance value was increased to 111.5%.

As discussed in the OECD 439, this in vitro test using Epi-200 tissues can be used to identify non-classified chemicals for member countries or regions, that do not adopt the optional UN GHS Category 3. As a consequence, the available test result indicates that neither irritation nor corrosion potential of the test substance is to be expected. Thus,the available data on the skin irritation of the substance is conclusive but not sufficient for classification according to the DSD (67/548/EEC) and CLP (1272/2008/EC) criteria.

Silicic acid, lithium salt (MR: 4.01) in a concentration of 25% was not irritating in an in vivo GLP-Guideline study (OECD 404) and does therefore not meet the criteria for classification according to Regulation (EC) 1272/2008 or Directive 67/548/EEC.

Eye

Taking into account the irreversibility of lesions observed in a study performed according to OECD Guideline 405, silicic acid, lithium salt (MR: 4.8) is classified as R41 "Risk of serious damage to eyes" according to the criteria of Directive 67/548/EEC (DSD) and as Eye Damage 1, H318 according to the criteria of Directive 1272/2008/EC (CLP).

Silicic acid, lithium salt (MR: 4.01) in a concentration of 25% is classified as Eye Irrit. 2, H319 according to the criteria of Directive 1272/2008/EC (CLP). According to the criteria of Directive 67/548/EEC (DSD) silicic acid, lithium salt (MR: 4.01) in a concentration of 25% does not meet the criteria for classification.

Respiratory system

There is no data on respiratory irritation available. However, since silicic acid, lithium salt (MR: 4.8) caused irreversible lesions to the eye, it can not be excluded, that silicic acid, lithium salt powder also damages the mucous membranes of the respiratory system, if inhaled. Therefore, for reasons of safety silicic acid, lithium salt powder is classified as R37 "Irritating to respiratory system" according to the criteria of Directive 67/548/EEC (DSD) and as STOT SE 3; H335: May cause respiratory irritation according to the criteria of Directive 1272/2008/EC (CLP).