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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

No test of biodegradability in water/sediment systems is available for the DTPMP potassium salt. The result is read across from the sodium salt. The substance has a low level of biodegradation in seawater, based on a degradation rate of 0% in 28d.

Key value for chemical safety assessment

Additional information

This conclusion is based upon a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

This substance is a member of a category of various ionised forms of the acid DTPMP (CAS 15827 -60 -8). The main assumption is that potassium is not significant in respect of all the properties under consideration. 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 (measured or expressed in aqueous media, e.g. ecotoxicity) for a salt can be directly read across (with suitable mass correction) to the parent acid and vice versa. Exposure of the soil would only be expected to occur via some form of aqueous processing (e.g. from spreading of WWTP sewage sludge). Thus it is acceptable to additionally read across between the parent acid and salts for the soil compartment. In the present context the effect of the counter-ion (potassium) will not be significant. In biological systems and the environment, polyvalent metal ions will be present, and the phosphonate ions show very strong affinity to them.