Sodium Salts of (1-Hydroxyethylidene)bisphosphonic acid (2-3 Na:1)

Endpoint summary

Description of key information

Short-term, reliable data for fish, invertebrates and algae are available for HEDP-H:

Fish: 96-hour LC₅₀ 195 mg active acid/L Oncorhynchus mykiss (freshwater), HEDP-H,

96-hour LC₅₀ 2180 mg active acid/L, Cyprinodon variegatus (marine), HEDP-H,

Invertebrates: 96-hour EC₅₀ 527 mg active acid/L, Daphnia magna (freshwater) HEDP-H,

96-hour LC₅₀ 1770 mg active acid/L, Palaemonetes pugio (marine), HEDP-H,

Algae: 96-hour E_rC₅₀ >132.22 mg active acid/L, Pseudokirchneriella subcapitata (freshwater), HEDP-H.

Long-term, reliable data are available for fish, invertebrates and algae for HEDP-H, its salts or structurally analogous substances:

Fish: (WOE) NOEC (60 d) 25.6 mg active acid/L, Oncorhynchus mykiss (freshwater), DTPMP-H,

(WOE) NOEC (60 d) 23 mg active acid/L, Oncorhynchus mykiss (freshwater), ATMP-H,

Invertebrates: 28-day NOEC 6.75 mg active acid/L, Daphnia magna (freshwater), HEDP-H,

96-hour (sublethal) EC₅₀ 130 mg active acid/L,Crassostrea virginica (marine), HEDP-H,

Algae: 96-hour NOE_rC 13.22 mg active acid/L, Pseudokirchneriella subcapitata (freshwater), HEDP-H

A weight of evidence approach is used for aquatic microbial inhibition studies. The available data supports a conclusion of an EC₀ value of at least 200 mg active acid/L in aerobic and anaerobic microorganisms under prolonged exposure in STP simulation tests.

For information about the read-across between HEDP-H and its salts, or from ATMP-H and DTPMP-H (for the long-term fish endpoint), please refer to IUCLID Section 13 and Annexes ** and ** of the CSR.

Additional information

The acid, sodium and potassium salts in the HEDP category are freely soluble in water and, therefore, the HEDP anion is fully dissociated from its sodium or potassium cations when in solution. Under any given conditions, the degree of ionisation of the HEDP species is determined by the pH of the solution. At a specific pH, the degree of ionisation is the same regardless of whether the starting material was HEDP-H, HEDP (1-2Na), HEDP (2-3Na), HEDP-4Na, HEDP-xK or another salt of HEDP.

 

Therefore, when a salt of HEDP is introduced into test media or the environment, the following is present (separately):

1. HEDP is present as HEDP-H or one of its ionised forms. The degree of ionisation depends upon the pH of the system and not whether HEDP (1-2Na), HEDP (2-3Na), HEDP-4Na, HEDP-xK salts, HEDP-H or another salt was added.
2. Disassociated sodium/potassium cations. The amount of sodium/potassium present depends on which salt was added.
3. Divalent and trivalent cations have much higher stability constants for binding with HEDP than the sodium or potassium ions, so would preferentially replace them. These ions include calcium (Ca²⁺), magnesium (Mg²⁺) and iron (Fe³⁺). Therefore, the presence of these in the environment or in biological fluids or from dietary sources would result in the formation of HEDP-dication (e.g. HEDP-Ca, HEDP-Mg) and HEDP-trication (e.g. HEDP-Fe) complexes in solution, irrespective of the starting substance/test material.

In this context, for the purpose of this assessment, read-across of data within the HEDP Category is considered to be valid.