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Description of key information

Phosphorwolframic acid hydrate shows a skin corrosive potential.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records
Reference
Endpoint:
skin corrosion: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 435 (In Vitro Membrane Barrier Test Method for Skin Corrosion)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Test system:
artificial membrane barrier model
Vehicle:
unchanged (no vehicle)
Details on test system:
The Corrositex® assay is a standardized in vitro corrosion test. The Corrositex® assay kit is commercially available from InVitro International.
The Corrositex® Biobarrier Membrane is a test system consisting of a reconstituted collagen matrix. The assay is based on the time that the test substance requires to penetrate through the Corrositex® Biobarrier Membrane and produce a change in the Chemical Detection System (CDS).
The Corrositex® assay is used to determine the corrosive potential of test substances. The assay is limited to testing materials which cause detectable pH changes in the CDS.

The experimental design of this study consisted of a qualification screen with the CDS (to determine if a color change can be detected) and a categorization screen (to categorize weak acids/bases and strong acids/bases) which were performed as a pretest (experimental conduct in accordance with GLP, but without a GLP status) and a definitive Corrositex® assay.
The Corrositex® assay was evaluated on the basis of the color change of the CDS. The time until a color change was observed was recorded manually and the breakthrough times of the four replicates were used to determine the corrosive potential of the test substance.

Test substance compatibility with the assay (qualification screen): For the qualification screen, 100 mg of the test substance were added to the CDS screening tube. If the test substance failed to produce a color change in the CDS within one minute the test substance could not be analyzed in this system and no further testing was required.

Categorization screen: The categorization screen was used to assess the appropriate scoring scale for the test substance.
The categorization screen was performed by adding 100 mg of test substance to tube A and B each. Each tube was mixed and the resulting color was observed. If required, 2 drops of the "confirm" reagent were added to tube B, the tube was mixed and the resulting color was observed.
The categorization kit and color chart provided by InVitro International were used to determine the category. The test substance was scored as category 1 (high acid/alkaline reserve) or category 2 (low acid/alkaline reserve).

Corrositex® assay
Following the acceptance of the positive control, the Corrositex® assay was performed for the test substance. Four vials containing the CDS were used for the test substance. In addition, one vial was used for the PC, the NC and the color (blank) control each. A membrane disc coated with the biobarrier matrix was placed into one vial containing the CDS. 500 mg undiluted test substance were added onto the membrane disc. An electronic time clock was started with the application. The vial was observed for three minutes for any change in the CDS. If no color change was observed within three minutes, the remaining membranes were treated with the test substance. An electronic time clock was started with each application. The vials were continuously observed for the first ten minutes. Thereafter, the vials were observed for approximately ten minutes around the time points relevant for evaluation or until breakthrough of the test substance occurred. The elapsed time between test substance application and the first change in the indicator solution (i.e. barrier penetration) was recorded.

positive control: one pellet of sodium hydroxide on top of the membrane disc. This vial was continuously monitored until breakthrough occurred.
negative control: 500 μL 10% citric acid. This vial was observed for 60 minutes and evaluated as “non-corrosive” if no reaction could be observed.
Control samples:
yes, concurrent negative control
yes, concurrent positive control
Amount/concentration applied:
500 mg undiluted test substance
Duration of treatment / exposure:
up to 4 hours or until breakthrough
Number of replicates:
4
Irritation / corrosion parameter:
penetration time (in minutes)
Run / experiment:
4 replicates
Value:
55.25
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid

Qualification screen: the test substance can react with the CDS and produce a visible color change.

Categorization screen: the test substance was assigned to timescale category 2 (having a low acid/alkaline reserve).

Breakthrough times of the test substance and the PC and NC

Test substance Break Through Time [min:s]
Vial 1 Vial 2 Vial 3 Vial 4 Mean
16/0488-1 58:10 54:08 54:26 54:16 55:15
Controls:          
PC:
Sodium hydroxide, solid
10:46 - - - -
NC:
10% citric acid
NB - - - -

NB = no breakthrough within maximum observation period (60 min)

Interpretation of results:
Category 1C (corrosive) based on GHS criteria
Conclusions:
Based on the results observed and by applying the evaluation criteria, it was concluded that Phosphorwolframic acid hydrate shows a corrosive potential in the Corrositex® - Skin Corrosion Test under the test conditions chosen. The mean breakthrough time determined in the in vitro membrane barrier test was 55 minutes and 15 seconds. -> GHS Cat. 1C
Endpoint conclusion
Endpoint conclusion:
adverse effect observed (corrosive)

Eye irritation

Endpoint conclusion
Endpoint conclusion:
no study available

Respiratory irritation

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

The potential of Phosphorwolframic acid hydrate to cause dermal corrosion was assessed by a single topical application of 500 mg of the test substance to the Corrositex® Biobarrier Membrane (Corrositex® assay).

The Corrositex® Biobarrier Membrane is a test system consisting of a reconstituted collagen matrix. The assay is based on the time that test substance requires to penetrate through the Corrositex® Biobarrier Membrane and produce a change in the Chemical Detection System (CDS).

In addition to the test substance, a positive and a negative control were assessed.

The Corrositex® assay showed the following results:

The qualification screen demonstrated that the test substance is able to react with the CDS and produce a visible color change. Therefore, the membrane barrier test method was determined to be suitable for the evaluation of the corrosive potential of the test substance. A timescale category test was carried out to distinguish between weak and strong acids or bases. The test substance was assigned to timescale category 2 (having a low acid/alkaline reserve.

In the main test, four Corrositex® Biobarrier Membranes were treated with the undiluted test substance. The mean breakthrough time of the test substance determined in the actual Corrositex® assay was 55 minutes and 15 seconds.

Based on the observed results and by applying the evaluation criteria, it was concluded that Phosphorwolframic acid hydrate shows a corrosive potential in the Corrositex® - Skin Corrosion Test under the test conditions chosen.

Justification for classification or non-classification

Based on the observed results and by applying the evaluation criteria, it was concluded that Phosphorwolframic acid hydrate shows a corrosive potential in the Corrositex® - Skin Corrosion Test under the test conditions chosen. The mean breakthrough time determined in the in vitro membrane barrier test was 55 minutes and 15 seconds. The breakthrough time indicates that the test substance has a weak corrosive potential and should be assigned to UN GHS skin corrosivity subcategories 1C or UN Transport Packing Group III as specified in the OECD TG 435 and Instruction Manual.