[nitrilotris(methylene)]trisphosphonic acid, ammonium salt

Endpoint summary

Description of key information

Limited data are available on the toxicity of ATMP-xNH₄ to aquatic organisms. ATMP-xNH₄ will dissociate as it is released into the aquatic environment and it is therefore necessary to assess the hazard properties of ATMP and ammonia separately. For hazard classification, ATMP-xNH₄ has been assessed based on the available aquatic data for the whole substance.

ATMP:

Short term toxicity to fish

A reliable 96-hour LC₅₀ value of 160 mg active acid/L has been determined for the effects of ATMP-H on mortality of Salmo gairdneri (now known as Oncorhynchus mykiss).

A 96-hour LC₅₀ value of >282 mg/L has been determined for the effects of ATMP-xNa salt on the mortality of the marine fish Cyprinodon variegatus.

Long term toxicity to fish

A 60-day NOEC value of 23 mg active acid/L has been determined for the effects of ATMP-H on growth of the fish O. mykiss. This study represents the only value available for this endpoint.

Short term toxicity to invertebrates

A 48-hour LC₅₀ value of 94 mg active acid/L has been determined for the effects of ATMP-H on mortality of the marine invertebrate Acartia tonsa. This study represents the lowest reliable value available for this endpoint.

A 48-hour EC₅₀ value of 297 mg active acid/L has been determined for the effects of ATMP-H on the immobility of the freshwater flea Daphnia magna.

A 48-hour EC₅₀ value of 66 mg/L has been determined for the effects of ATMP-xNH₄ on the mobility of the freshwater flea Daphnia magna. This value is used for the purposes of Classification and Labelling and is reported in terms of the test material (ammonium salt), rather than as ATMP active acid, as the ammonia drives the toxicity of the substance in the test.

Long term toxicity to invertebrates

A 28-day NOEC value of ≥ 25 mg active acid/L has been determined for the effects of ATMP-H on adult survival and reproduction of D. magna. The study represents the lowest reliable value available for this endpoint.

A 96-hour NOEC value of 96 mg active acid/L has also been determined for the effects of ATMP-H on the growth of the marine eastern oyster Crassostrea virginica.

Toxicity to algae and cyanobacteria

72-hour EC₅₀ and NOEC values of 80 and 40 mg active acid/L respectfully, have been determined for the effects on ATMP-H on the growth rate of Skeletonema costatum. This value represents the lowest reliable value available for this endpoint. Another study determined a 96-hour EC₅₀ value 12.39 mg active acid/L for the effects of ATMP-H on the biomass of Pseudokirchneriella subcapitata, however, this value was not deemed reliable and is not used as the key value for this endpoint.

Additional information

ATMP-xNH₄ will dissociate when it is released into aqueous environments to yield ATMP and ammonia.

Ammonia:

The toxicity of the ammonium salt will be significantly influenced by the presence of ammonia that is liberated following dissociation and its contribution therefore needs to be taken account of when determining hazard and when setting PNECs for risk characterisation. For hazard classification, ATMP-xNH₄ has been assessed based on the available aquatic data for the whole substance.

 

Ammonia ecotoxicity data have been reviewed in two programmes of peer review: the Environment Agency Proposed EQS for Water Framework Directive Annex VIII Substances: Ammonia (unionised) 2007 (EA, 2007) and the OECD/HPV SIAR for the Ammonia category (OECD, 2007; sponsored by, shared partnership with European Fertilizers Manufacturing Association (EFMA-Europe) and The Fertilizer Institute (TFI-US)). Further review of the data has not been considered necessary.

 

The following aquatic data have been selected as the lowest reliable freshwater values (expressed in terms of unionised NH₃) available from the peer-reviewed report 'Environment Agency Proposed EQS for Water Framework Directive Annex VIII Substances: Ammonia (unionised) 2007' (EA, 2007):

Short-term

Fish: 96-hour LC₅₀ 0.068 mg NH₃-N/L, Oncorhynchus gorbuscha (equivalent to 0.083 mg NH₃/L)

Invertebrates: 96-hour LC₅₀ 0.16 mg NH₃-N/L, Hyalella azteca

Algae: 5-day EC₅₀ 2.0 mg NH₃-N/L, Chlorella vulgaris

Long-term

Fish: 73-day LOEC 0.022 mg NH₃-N/L, Oncorhynchus mykiss (equivalent to 0.027 mg NH₃/L). This value is converted to a NOEC value by applying a factor of 2, therefore the 73-day NOEC value is 0.0135 mg NH₃/L.

Invertebrates: 29-day NOEC 0.066 mg NH₃-N/L, Deleatidium sp.

Algae: 14-day LOEC 3.0 mg NH₃-N/L, mixed algal populations

Peer-reviewed aquatic ecotoxicity data have also been reviewed in the OECD SIDS (2007) report, however the data from the Environment Agency (2007) report represent the lowest available data for these endpoints. Across both datasets, fish were the most sensitive trophic level in both short- and long-term tests. Therefore, the long-term fish data has been used as the basis of the aquatic PNEC values.

The toxicity of the ammonium salt is discussed further in IUCLID Section 6.0 Ecotoxicological Information and section 7.0 of the CSR.

The acid, sodium, potassium and ammonium salts in the ATMP category are freely soluble in water. The ATMP anion can be considered fully dissociated from its sodium, potassium or ammonium cations when in dilute solution. Under any given conditions, the degree of ionisation of the ATMP 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 ATMP-H, ATMP.4Na, ATMP.7K or another salt of ATMP.

 

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

1. ATMP is present as ATMP-H or one of its ionised forms. The degree of ionisation depends upon the pH of the media and not whether ATMP (3-5K) salt, ATMP (3-5Na) salt, ATMP-H (acid form), or another salt was used for dosing.
2. Disassociated potassium, sodium or ammonium cations. The amount of potassium or sodium present depends on which salt was dosed.
3. It should also be noted that divalent and trivalent cations would preferentially replace the sodium or potassium ions. These would include calcium (Ca²⁺), magnesium (Mg²⁺) and iron (Fe³⁺). These cations are more strongly bound by ATMP than potassium, sodium and ammonium. This could result in ATMP-dication (e.g. ATMP-Ca, ATMP-Mg) and ATMP-trication (e.g. ATMP-Fe) complexes being present in solution.

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