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

Toxicity to birds

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to birds

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Additional information

In accordance with Column 2 of REACH Annex X, long-term and reproductive toxicity testing with birds (required in Section 9.6) is not needed because a large mammalian dataset is available with the submission substance, therefore further in vivo testing on birds is not considered necessary or justified on ethical grounds. In addition, the substance has low potential for bioaccumulation (based on log K_ow <3, and a low bioaccumulation factor from fish BCF testing (BCF <100)) and therefore does not require further consideration for assessment of secondary poisoning. Additionally, two reliable supporting studies indicate no toxic effects of HEDP-H to two bird species (Anas platyrhynchos and Colinus virginianus) after 14 days' exposure up to concentrations of 284 mg/kg bw/day.

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.