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DTPMP and its salts are of low short-term toxicity to fish and aquatic invertebrates. The lowest reliable short-term toxic concentrations determined for DTPMP are a 96-h LC50 for the rainbow trout, Oncorhynchus mykiss, that is in the range 180-252 mg/L and a 48-h EC50 for Daphnia magna of 252 mg/L (however the latter is thought to be due to pH and the study has been assigned reliability 4). DTPMP is of low long-term toxicity to fish (O. mykiss 60-day NOEC: 25.6 mg/L). There are no available long-term data for aquatic invertebrates.

Ammonia

The toxicity of the ammonium salt will however 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 this will be achieved by treating the substance as a preparation, i.e. on the basis of proportion of ammonia present, as stipulated in its Annex I (DSD)/Annex VI () entry.

Ammonia ecotoxicity data have been reviewed in the OECD/HPV programme of peer review. The best available data are summarised in the SIAR for the Ammonia category (OECD, 2007a; 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.

Toxicity of ammonia is dependent on the degree of ionization and, therefore, is highly pH dependent and also dependent on temperature. Long-term exposure of fish to ammonium compounds may induce reproductive changes starting at 100 mg/l. EC50 values for invertebrates range from 21.8 mg total NH3/L for ammonium chloride to > 25.7 mg total NH3/L for ammonium sulfate. Long-term studies with invertebrates showed slightly lower NOEC values of 3.1-3.47 mg total NH3/L. The algae, Chlorella vulgaris, EC50 (biomass; 0-5d) was 1300 mg/l using ammonium chloride. In a 21-day test with Chlorella vulgaris and ammonium sulfate, an EC50 of 25,476 mg/l (2700 mg N/L) was established from exponential growth on day 11-18. Ammonia that is unionised is toxic to aquatic organisms at concentrations below 1 mg/l (OECD, 2007a).

Algae

The effects of DTPMP observed in tests with algae are likely to be a consequence of nutrient limitation caused by complexation and not true toxicity. Thus, a 95-hour ErC50 for Selenastrum capricornutum (now known as Pseudokirchneriella subcapitata) of 0.45 mg/L is likely to over-estimate the true toxicity. The toxicity of DTPMP and its salts to algae is best represented by the 95 hour ErC50 value of >10 mg/L. This value was obtained in the only test where steps were taken to counter the effects of nutrient complexation and it is therefore most likely to be indicative of true toxicity.

There are no reliable data describing the short-term toxicity of DTPMP to sewage sludge micro-organisms. However data has been read-across from other phosphonic acid. The data indicate a low level of toxicity (approx. 100 mg /l).

The 2Na and 7Na salts of DTPMP are of low short-term toxicity to sediment-dwelling invertebrates (C. volutator 10-day LC50::>2500 mg/kg d.w).

No data are available that describe the toxicity of DTPMP to terrestrial plants and invertebrates. DTPMP is oflow short-term toxicity to birds when administered via the dietary exposure route (Anas platyrhynchos and Colinus virginianus 14-day LC50: >454 mg/kg bw). DTPMP is not expected to be bioaccumulative in longer-term studies, based on its low log Kow

The category hypothesis is that all the members are various ionised forms of the acid CAS 15287-60-8. The main assumption is that sodium and potassium are not significant in respect of all the properties under consideration. DTPMP salts will dissociate into DTPMP and the counter-ion when in contact with aqueous and moist media, therefore the two substances should be assessed separately. In dilute aqueous conditions of defined pH a salt will behave no differently to the parent acid, at identical concentration of the particular speciated form present and will be fully dissociated. Hence some properties for a salt can be directly read-across (with suitable mass correction) to the parent acid and vice versa. The ammonium salt does present a particular issue since it drives the toxicity of the substance. The toxicity of the ammonium salt is discussed further in the CSR (section 7).