Polyphosphoric acids

Endpoint summary

Description of key information

Skin irritation / corrosion
0.5 mL of a 80% phosphoric acid solution was observed to be corrosive to rabbit skin after 24 hours of exposure. 
Eye irritation:
No reliable data are available for the eye irritation endpoint. Nevertheless as the substance is skin corrosive and classified accordingly, the substance is as well considered as eye corrosive. This is as well in accordance with the results of the unreliable studies.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation: in vivo

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study performed according to 1500.41 in the Federal Register Vol. 38, No. 187, S. 26019 from 1973-09-27 with limited documentation.

Qualifier:

according to guideline

Guideline:

other: 1500.41 in the Federal Register Vol. 38, No. 187, S. 26019 from 1973-09-27

Deviations:

not specified

GLP compliance:

not specified

Species:

rabbit

Strain:

Vienna White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: no data
- Age at study initiation: no data
- Weight at study initiation: 2.45-3.14 kg (mean: 2.79 kg)
- Housing: no data
- Diet: SSNIFF diet (Intermast), witheld during the contact period
- Water: withheld during the contact period
- Acclimation period: no data

ENVIRONMENTAL CONDITIONS
- Temperature (°C): no data
- Humidity (%): no data
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): no data

IN-LIFE DATES: From: 1979-07-03 To: 1979-07-06

Type of coverage:

not specified

Preparation of test site:

other: all test sites were shaved, half of the test sites were abraded

Vehicle:

unchanged (no vehicle)

Controls:

not required

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 0.5 mL
- Concentration (if solution): 80 %

VEHICLE
- Amount(s) applied (volume or weight with unit): not applicable
- Concentration (if solution): not applicable
- Lot/batch no. (if required): not applicable
- Purity: not applicable

Duration of treatment / exposure:

24 hours

Observation period:

- Observations were performed at 24 and 72 hours and at 8 days post-dosing.

Number of animals:

6 males

Details on study design:

TEST SITE
- Area of exposure: 2.5 x 2.5 cm
- % coverage: no data
- Type of wrap if used: the test sites were covered with a rubberized covering (5 x 5 cm), fixed with bandaid strips, and wrapped with gauze.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): no data
- Time after start of exposure: no data

SCORING SYSTEM:
- The scoring system appears to be equivalent to the Draize scale.

Irritation parameter:

erythema score

Remarks:

(intact and abraded)

Basis:

mean

Time point:

other: 24 and 72 hours

Score:

4

Max. score:

4

Reversibility:

not reversible

Remarks:

within 72 hours post-dosing

Irritation parameter:

edema score

Remarks:

(intact)

Basis:

mean

Time point:

other: 24 hours

Score:

2.8

Max. score:

4

Reversibility:

not fully reversible within: 72 hours post-dosing

Remarks on result:

other: 1 score was 2, 5 scores were 3

Irritation parameter:

edema score

Remarks:

(intact)

Basis:

mean

Time point:

other: 72 hours

Score:

2.3

Max. score:

4

Reversibility:

not fully reversible within: 72 hours post-dosing

Remarks on result:

other: 4 scores were 2, 2 scores were 3

Irritation parameter:

edema score

Remarks:

(abraded)

Basis:

mean

Time point:

other: 24 hours

Score:

3

Max. score:

4

Reversibility:

not fully reversible within: 72 hours post-dosing

Remarks on result:

other: all scores were 3

Irritation parameter:

edema score

Remarks:

(abraded)

Basis:

mean

Time point:

other: 72 hours

Score:

2.2

Max. score:

4

Reversibility:

not fully reversible within: 72 hours post-dosing

Remarks on result:

other: 5 scores were 2, 1 score was 3

Irritation parameter:

primary dermal irritation index (PDII)

Time point:

other: 72 hours

Score:

6.6

Irritant / corrosive response data:

Intact and Abraded Test Sites:
- In intact and abraded sites at 24 hours, edema and mild necrosis was observed in all animals.
- In intact sites at 72 hours, edema was observed in 3 animals and deep tissue necrosis was observed in the other 3 animals with gross pathological effects.
- In abraded sites at 72 hours, deep tissue necrosis was observed in all animals with accompanying edema in 1 animal. The necrosis was observed with gross pathological effects.

Other effects:

- All animals were sacrificed at 72 hours for humane reasons.

Interpretation of results:

corrosive

Remarks:

Migrated information 80% phosphoric acid Criteria used for interpretation of results: not specified

Conclusions:

The test substance was corrosive to the rabbit skin.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (corrosive)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Polyphosphoric acid is a mixture of the corresponding acids to phosphate anion and its condensed phosphates as follows:

- orthophosphoric acid or phosphoric acid (17 -76%),

- pyrophosphoric acid (23 -50%),

- triphosphoric acid (1.5 -25%),

- tetraphosphoric acid (0 -12%)

- and pentaphosphoric acid (0 -7%).

 

When the substance polyphosphoric acid is in contact of excess of water, a rapid hydrolysis is observed with the longer chains (tri, tetra or penta) while a very slow hydrolysis is observed for the dimer form to ortho phosphate. However, in biological media, the pyrophosphate ion is cleaved rapidly into two orthophosphate molecules by one of the different members of the alkaline phosphatase family which are present in all tissues. Thus a read across from phosphoric acid to pyrophosphoric acid is justified.

All the data discussed below were generated with phosphoric acid.

Skin irritation / corrosion:

BASF (1980) studied the skin irritant/corrosive properties of phosphoric acid on Vienna White rabbit skin (6 male rabbits tested according to guideline 1500.41 in the Federal Register Vol. 38, No. 187, S. 26019 from 1973 -09 -27). 0.5 mL of an 80% solution was applied to the shaved test sites (half of the test sites were abraded). After 24 hours of exposure, observations were done at 24 and 72 hours and at 8 days post dosing. The substance was observed to be corrosive to rabbit skin. These data were considered as key information for the skin irritation/corrosion endpoint. BASF (1980) studied as well the skin irritation properties of 0.5 mL 19% solution of phosphoric acid in 2 female Vienna White rabbit (4 hours of exposure). The test substance was considered as a non skin irritant substance.

Eye irritation:

Phosphoric acid is classified as a skin corrosive substance category 1B (concentration > or = 25%) and an eye irritant (10% < or = concentration < 25%) according to the CLP Regulation Annex VI, table 3.1 (EC Regulation 1272/2008 on classification, labelling and packaging of substances and mixtures). Therefore, according to the REACH Regulation, in vitro testing for eye irritation with this substance does not need to be conducted (column 2 adaptation, Annex VII, section 8.2). In vivo testing can be waived according to the REACH Regulation as phosphoric acid is classified as corrosive to the skin and as an eye irritant (column 2 adaptation, Annex VIII, section 8.2.1).

Justification for selection of skin irritation / corrosion endpoint:
Read-across justified from phosphoric acid to polyphosporic acid.

Effects on skin irritation/corrosion: corrosive

Effects on eye irritation: corrosive

Justification for classification or non-classification

According to the available data, phosphoric acid is considered as a skin corrosive substance (80% solution tested). This is in the line with the Harmonized CLP classification where phosphoric acid is classified as a Skin Corrosive substance category 1B. In addition, the harmonized classification (Table 3.1 of the CLP Regulation (EC) No 1272/2008 reports that phosphoric acid is a skin irrtant substance category 2 at following concentration limits: 10% < or = C <25% although the available data didn't show an irritant effect at a concentration of 19% phosphoric acid. The classification of the CLP Regulation will nevertheless be followed in this substance dossier.

According to the CLP Regulation (EC) 1272/2008, phosphoric acid is considered as an eye irritant substance category 2 with a concentration limit of 10% < or = C < 25% (Annex VI harmonized classification (Tabel 3.1))

In conclusion and based on the read across perfomed, pyrophosphoric acid will be classified as phosphoric acid.