Polyphosphoric acids

Endpoint summary

Description of key information

Low acute toxicity via oral route (LD50 = 2600 mg/kg); limited exposure via inhalation; study by dermal route not necessary due to low systemic toxicity and corrosive nature.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

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

Adequacy of study:

key study

Study period:

N/A to 1968-04-18

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Non-GLP study similar to OECD 423 with sufficient documentation on methods and results to evaluate data.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 423 (Acute Oral toxicity - Acute Toxic Class Method)

Deviations:

not specified

GLP compliance:

no

Test type:

acute toxic class method

Limit test:

no

Species:

rat

Strain:

other: SPF-Wister K

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Weight at study initiation: 80-134 g
- Fasting period before study: 12 hrs
- Diet: After application rats received the standard-ALTROMIN R feed
- Water: tap water

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

VEHICLE
- Concentration in vehicle: 10% aqueous solution
- Amount of vehicle (if gavage): 0.8 to 5.0- mL/100g-bw

Doses:

0.8, 1.25, 2.0, 3.2, and 5.0 mL per 100 g body weight

No. of animals per sex per dose:

10 female rats

Control animals:

not specified

Details on study design:

- Duration of observation period following administration: 7 days

Sex:

female

Dose descriptor:

LD50

Effect level:

1.7 other: mL/100 g body weight

Remarks on result:

other: corresponding approximately to 2600 mg/kg

Mortality:

In the 0.8 mL/100 g-bw dose group there was no mortalities and in the 1.25 mL/100 g-bw group 2 of the 10 animals died. In the 2.00 mL/100 g-bw dose group 8 of the 10 animals died and in the 3.20 mL/100 g-bw and 5.0 mL/100 g-bw dose group all 10 of the animals died.

Clinical signs:

other: The animals died unbalanced, lying on tummy or flank, with breathing difficulties and cramps within 30 minutes to 24 hours after application.

Gross pathology:

The necropsy of the animals showed macroscopic strong chemical burns on the mucous membrane of the stomach.

Interpretation of results:

not classified

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

The LD50 for a 10% solution of 75.4% thermal phosphoric acid in rats was determined to be 1.70 ml/100 g body weight (approximately 2600 mg/kg bw).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

Although most of the studies are quoted Klimisch K3 or K4, All support the evidence of a low acute oral toxicity.

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Acute toxicity: via dermal route

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 polyphosphoric acid is justified.

All the data discussed below were generated with phosphoric acid.

 

 

Acute toxicity: oral

Several oral acute toxicity studies are available for phosphoric acid but most of them are poorly reported especially concerning the purity of the test item. However, all support the evidence that LD50 of phosphoric acid is around or above 2000 mg/kg. The study from laboratory for Commercial and Pharmaceutical Toxicology (1968) has been considered as key study as sufficient and reliable information were given. In this study an LD50 of 1.70 ml/100 g body weight in SPF-Wister K rats was observed for a 10% solution of 75.4% thermal phosphoric acid corresponding to approximately 2600 mg/kg. The study was performed according to OECD Guideline 423 although it was not performed under GLP.

 

Acute toxicity: inhalation

Several acute toxicity studies by inhalation were performed for phosphoric acid but most of them are poorly reported especially concerning the purity of the test item. Thus, no reliable data are available for phosphoric acid for acute inhalation toxicity.

According to the REACH Regulation, an acute toxicity test does not generally need to be conducted if the substance is classified as corrosive to the skin (column 2 adaptation, Annex VIII, section 8.5). Risk Management Methods should be implemented to eliminate the risk of acute systemic toxicity from inhalation.

 

Acute toxicity: dermal

Several acute dermal toxicity studies were performed for phosphoric acid but most of them are poorly reported especially concerning the purity of the test item. Thus, no reliable data are available for phosphoric acid for acute dermal toxicity.

There is no reliable dermal LD 50 value for acute skin toxicity for phosphoric acid, and due to the corrosive nature of the substance it is not ethical to carry out this animal study. Acute toxicity by oral route resulted to a LD50 of 2600 mg/kgbw indicating relative low acute systemic toxicity for which no classification is required. Use and handling of the pure substance is only industrial and professional (formulation), and the classification corrosive of the pyrophosphoric and phosphoric acids requires risk management methods which eliminate the risk of acute systemic toxicity from potential for skin contact. Therefore, there is no need to perform an acute dermal toxicity test with phosphoric acid according to the REACH Regulation (column 2 adaptation, Annex VIII, section 8.5).

Justification for selection of acute toxicity – oral endpoint
Non-GLP study similar to OECD 423 with sufficient documentation on methods and results to evaluate data.

Justification for selection of acute toxicity – inhalation endpoint
No exposure.

Justification for selection of acute toxicity – dermal endpoint
Study scientiffically unjustified.

Justification for classification or non-classification

As the acute oral LD50 > 2600 mg/kg bw, phosphoric acid should not be classified according to the CLP Regulation (EC) No 1272/2008 for this endpoint.