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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

No simulation studies of biodegradation in water / sediment were available for the registration substance. Studies using the parent acid form of the structurally analogous aminomethylenephosphonate HMDTMP demonstrate that slow but significant levels of degradation occur, particularly under light-exposed conditions, indicating that removal in the environment is to be expected. Half-lives have not been quantitatively determined however.

Key value for chemical safety assessment

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.

 

HMDTMP-H (CAS 23605-74-5) has two aminobismethylphosphonate groups, connected by a hexyl chain. BHMT acid (CAS 34690-00-1) has three amine centres (five methylphosphonate groups), connected by hexyl chains.

 

As well as being structural analogues, both phosphonates have consistent chemical properties including high MW (492 and 685 respectively), very low log Kow(≤-4 for both substances) and are highly soluble in water. The substances generally posses similar physico-chemical properties and are not readily biodegradable.

 

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.