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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

No study of bioaccumulation conducted with EDTMP-xCaxNa is available. Given the very low estimated value of log Kow (-4), bioaccumulation is expected to be very low. A reliable study of bioaccumulation of DTPMP-xNa in carp, indicates a bioconcentration factor in the exposure phase of <10 (Concentration level 18.8mg/l) and <94 (concentration level 2.03 mg/l). No active uptake mechanisms (i.e. mediated by enzymes) can occur for phosphonates. 

Key value for chemical safety assessment

BCF (aquatic species):
94 dimensionless

Additional information

The registration substance is part of a category family (super-category; see CSR for more details) which consists of several phosphonates that share a common chemistry incorporating alkyl backbones with one or more tertiary amine centres and multiple methylphosphonate groups present.

EDTMP acid (CAS 1429-50-1) has two aminobismethylphosphonate groups, connected by an ethylidene chain. DTPMP acid (CAS 15827-60-8) has three amine centres (five methylphosphonate groups), connected by ethyl chains.

As well as being structural analogues, both phosphonates have consistent chemical properties including high MW (436 and 573 respectively), very low log Kow(≤-3 for both substances) and are highly soluble in water. The substances generally possess similar physico-chemical properties and are not readily biodegradable.

The sodium counterion of these phosphonates is not significant in respect of the properties under consideration and has been assessed in depth in the public literature. Additionally, the counterion is expected to dissociate when in contact with water, including atmospheric moisture.In view of the high levels of calcium ions typically present in natural waters and test media, the Ca2+ion is not expected to be significant.

Therefore, for the purpose of this assessment, read-across is considered valid.

Further information on the super-category and the validity of read-across are presented in the CSR Chapter 1.

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