Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

No data are available regarding Absorption/Desorption of HEBMP-H so Kd for the substance is derived from Kd of its sodium salts (cyclic form and linear form): average Kd for linear structure is 1500 l/kg and for cyclic structure is 110 l/kg.

Additional information

Adsorption coefficients have been derived in a reliable OECD 106 test in soil-water systems under a range of conditions. At low concentrations of the range predicted to occur in the environment, the average Kd has been extrapolated to 1500 l/kg (for the linear constituent structure). For the cyclic constituent, the equivalent value was 110 l/kg based on a preliminary test at higher concentration. Adsorption and desorption behaviour of the cyclic constituent is not yet fully understood and until/unless definitively proven otherwise, the chemical safety assessment assumes at this stage that some desorption of cyclic constituent from the substrate is possible. This is a conservative interpretation and is not the case for the linear constituent (and other aminomethylenephosphonates) which show negligible desorption and effectively irreversible binding. Under the negatively-charged, alkaline conditions at the surface of mineral substrate, it would be thermodynamically favourable for the ring structure present in the cyclic constituent molecule to open, and behaviour like the linear constituent is then to be expected.