Silicon orthophosphate

Endpoint summary

Description of key information

Skin irritation (OECD 402): not irritating
Eye irritation (OECD 437): corrosive

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 437 (Bovine Corneal Opacity and Permeability Test Method for Identifying Ocular Corrosives and Severe Irritants)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit, München, Germany

Species:

other: isolated bovine corneas

Strain:

not specified

Vehicle:

physiological saline

Controls:

other: number of eyes for the test item: 3

Amount / concentration applied:

TEST MATERIAL
- Concentration (if solution): 20%

VEHICLE
- Amount(s) applied (volume or weight with unit): 750 µL test item preparation

Duration of treatment / exposure:

4 hours ± 5 minutes at 32 ± 1 °C

Observation period (in vivo):

not applicable

Number of animals or in vitro replicates:

not applicable

Details on study design:

Fresh eyes from the slautherhouse were transported in HBSS containing Pen/Strep on ice to the laboratories. Immediately after arrival of the eyes, cornea preparation was initiated. The tissue surrounding the eyeball was carefully pulled away and the cornea was excised leaving a 2 to 3 mm rim of sclera. The isolated corneas were stored in a petri dish containing HBSS. Before the corneas were mounted in the corneal holders, they were carefully examined for defects and any defective eyes were discarded. The chambers were filled with RPMI containing 1% FBS and 2 mM L-glutamine and incubated for one hour at 32 ± 1°C in a water bath. After the equilibration period, the medium was removed from the chambers and replaced by fresh medium. An initial opacity measurement was performed on each of the corneas using the calibrated opacitometer. Afterwards 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 was washed three times with medium. Once the medium was free of test substance, the cornea was fully rinsed with complete RPMI and opacity measurement was performed. Afterwards, the medium was removed from the chambers and filled with fresh medium. 1 mL of a 5 mg/mL sodium fluorescein solution was added to the anterior chamber and the corneas were incubated for 90 minutes at 32 ± 1°C. Then the medium was removed and its optical density at 490 nm was determined, using a spectrophotometer. 3 corneas each were used for the test item, as negative control treated with physiological saline 0.9% NaCl or as positive control treated with imidazole 20% in physiological saline 0.9% NaCl.

The change in opacity for each cornea was calculated by subtracting the initial opacity reading from the final opacity reading. These values were corrected by subtracting from each the average change in opacity observed for the negative-control corneas. The mean opacity value for each treatment was calculated by averaging the corrected opacity values of each cornea for a given treatment.
The mean OD490 for the blank wells were calculated. The mean blank OD490 was subtracted from the OD490 of each well (corrected OD490). Any dilutions that were made to bring the OD490 values into the linear range of the spectrophotometer (OD490 should be less 1.500), were taken into account by multiplying the OD490 value of the dilution by the dilution factor. The final-corrected OD490 of the test article and the positive control were calculated by subtracting the average corrected OD490 of the negative control corneas from the corrected OD490 value of each treated cornea: final-corrected OD490 = (OD490 - mean blank OD490) - average-corrected negative control OD490. The mean OD490 value of each treatment group was calculated by averaging the final corrected OD 490 values of the treated corneas for that treatment condition. The following formula was used to determine the in vitro irritation score (IVIS): IVIS= mean opacity value + (15x mean OD490 value). Evaluation of the mean scores as follows: 0-3 = non irritant, 3.1-25 = mild irritant, 25.1 – 55 = moderate irritant, 55.1 – 80 = severe irritant, >80.1 = very severe irritant.

Irritation parameter:

other: opacity

Basis:

other: mean out of all 3 eyes

Time point:

other: 4 h

Score:

93.33

Reversibility:

other: not applicable

Remarks on result:

other: Test substance

Irritation parameter:

other: permeability

Basis:

other: mean out of all 3 eyes

Time point:

other: 4 h

Score:

-0.014

Reversibility:

other: not applicable

Remarks on result:

other: Test substance

Irritation parameter:

other: IVIS

Basis:

other: mean out of all 3 eyes

Time point:

other: 4 h

Score:

93.13

Reversibility:

other: not applicable

Remarks on result:

other: Test Substance

Irritation parameter:

other: opacity

Basis:

other: mean out of all 3 eyes

Time point:

other: 4 h

Score:

164.67

Reversibility:

other: not applicable

Remarks on result:

other: Positive control

Irritation parameter:

other: permeability

Basis:

other: mean out of all 3 eyes

Time point:

other: 4 h

Score:

1.966

Reversibility:

other: not applicable

Remarks on result:

other: Positive control

Irritation parameter:

other: IVIS

Basis:

other: mean out of all 3 eyes

Time point:

other: 4 h

Score:

194.16

Reversibility:

other: not applicable

Remarks on result:

other: Positive control

Table 1: Opacity data

Cornea No.	Test item	Initial Opacity	Final Opacity	Change of Opacity Value	Corrected Oapcity Value
1	Negative Control	3	3	0
2		3	4	1
3		3	3	0
Mean Value		3.00	3.33	0.33
4	Positive Control	3	199	196	195.67
5		3	150	147	146.67
6		3	155	152	151.67
Mean Value		3.00	168.00	165.00	164.67
7	Test Item	2	102	100	99.67
8		2	102	100	99.67
9		2	83	81	80.67
Mean Value		2.00	95.67	93.67	93.33

Table 2: Permeability data

Cornea No.	Test Item	OD490	Corrected OD490 Value
1	Negative Control	0.026
2		0.010
3		0.011
Mean Value		0.016
4	Positive Control	1.996	1.980
5		1.870	1.854
6		2.079	2.063
Mean Value		1.981	1.966
7	Test Item	0.003	-0.013
8		0.002	-0.014
9		0.001	-0.015
Mean Value		0.002	-0.014

Table 3: In vitro irritation score

Cornea No.	Test Item	Corrected Opacity Value	Corrected OD490 Value	IVIS
1	Negative Control	0.00	0.026
2		1.0	0.010
3		0.00	0.011
Mean Value		0.33	0.016	0.57
4	Positive Control	195.67	1.980
5		146.67	1.854
6		151.67	2.063
Mean Value		164.67	1.966	194.16
7	Test Item	99.67	-0.013
8		99.67	-0.014
9		80.67	-0.015
Mean Value		93.33	-0.014	93.13

Interpretation of results:

corrosive

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

CLP: Cat. 1, H318
DSD: Xi, R41

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin

No in vivo skin irritation is required for silicon orthophosphate since an acute toxicity study by the dermal route does not indicate irritating properties up to the limit dose level of 2000 mg/kg bw.

According to OECD 402, 2000 mg/kg bw of the test substance was dermally applied to the intact skin of 5 male and 5 female rats each (Lütkenhaus, 2012). The test substance was placed on a wet gauze patch and applied to the skin for 24 h under occlusive conditions. After the exposure period, the gauze patch was removed and the treated skin was rinsed with water. Erythema grade 1 was observed in 1 of 5 female animals 48 and 72 h after patch removal. This effect was fully reversible within 120 h after application of the test substance. Edema was not observed. Scratches and eschar were observed in all male and female animals from day 3 to day 9 at the latest. Hence, all signs of irritation were reversible within the observation period of 14 days.

Eye

Eye irritating properties of the test substance were investigated in a GLP-compliant bovine corneal opacity and permeability assay (OECD 437, Lütkenhaus, 2012). Isolated corneas from freshly slaugthered cattles were exposed to a 20% test substance solution for 4 hours. After the exposure period, corneal opacity was measured quantitatively as the amount of light transmission through the cornea and permeability was quantitatively measured as the amount of sodium fluorescein dye that passes across the full thickness of the cornea. After correction for background values of the negative control, the mean opacity value and mean permeability OD490 value were taken into consideration and an in-vitro irritancy score (IVIS) of 93.13 was calculated. Substances with an IVIS of ≥ 55.1 are regarded as severe eye irritant. An appropriate positive control was also included into the study design and revealed the expected results (IVIS: 194.16). Thus, under the test conditions of the assay, the test substance was considered to cause serious eye damage.

Justification for selection of skin irritation / corrosion endpoint:
There is an acute toxicity study for the test substance by the dermal route avilable, that does not indicate skin irritation up to the limit dose level of 2000 mg/kg bw.

Justification for selection of eye irritation endpoint:
There is only one study available.

Effects on eye irritation: corrosive

Justification for classification or non-classification

The available data on skin irritation of the test substance do not meet the criteria for classification according to Regulation (EC) 1272/2008 or Directive 67/548/EEC, and are therefore conclusive but not sufficient for classification.

The available data on eye irritation of the test substance are conclusive and meet the criteria for classification. The substance has to be classified as Eye irritant Cat. 1 (H318: Causes serious eye damage) according to Regulation (EC) 1272/2008 and as Eye irritant (Xi, R41: Risk of serious damage to eyes) according to Directive 67/548/EEC.