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Short-term toxicity to aquatic invertebrates

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Description of key information

A 48-hour EC50 value of 66 mg/L and NOEC of 18 mg/L have been determined for the effects of the strcuturally analogous substance ATMP-xNH4 on mobility of Daphnia magna (reliability 2, SafePham Laboratories 1995).
A reliable 48 h EC50 value of 7590 mg active acid/l has been determined for the effects of DTPMP acid, the parent substance of DTPMPxNH4, on the mortality of the freshwater insect Chironomus tentans (reliability 2, EG&G 1976).
A reliable 48 h EC50 value of >252 mg active acid/l has been determined for the effects of DTPMP-xNa on the immobility of the marine copepod Acartia tonsa.

Key value for chemical safety assessment

Additional information

No data are available for the registered substance DTPMPxNH4, however, data are available for the structurally related substance ATMP-xNH4 and for the parent acid substance DTPMP. The data provided indicate that it is the ammonium salt driving the toxicity rather than the DTPMP. Data for DTPMP and its sodium sodium salt have produced EC50 values of 7589 mg active acid/L with the freshwater insect Chironomus tentans and >252 mg active acid/L with the marine copepod Acartia tonsa.

ATMP-xNH4 will dissociate when it is released into aqueous environments to yield ATMP and ammonia.The assessment of short-term toxicity of the substance to aquatic organisms and the resulting hazard classification are therefore, in the absence of an adequate set of test data, based on treating the substance as a preparation. Test data do not indicate that DTPMP acid is toxic to invertebrates following short-term exposure. However, the un-ionised ammonia moiety is however known to be toxic to aquatic organisms and concentration limits, as stipulated in the Annex I (DSD)/Annex VI (CLP) entry for ammonia.

DTPMP and ammonia will also be treated separately for the purposes of deriving PNECs for the aquatic compartment. A PNECaquatic for ammonia has already been derived by the UK Environment Agency for the purpose of setting an Environmental Quality Standard (EQS) under Annex VIII of the Water Framework Directive (WFD). The relevant data are presented in section 7.6 of the CSR. This PNEC is also considered to be adequate for the purpose of risk characterisation of ammonia present in DTPMP-xNH4. A PNEC for DTPMP will be determined using test data for the substance.

Read-across justification between DTPMPxNH4 (CAS 70714-66-8) and ATMPxNH4 (CAS 34274-28-7):

DTPMP acid (CAS 15287-60-8) has three amine centres (five methylphosphonate groups), connected by ethyl chains. ATMP acid (CAS 6419-19-8) has has three methylphosphonate groups connected by a central amine nitrogen. As well as being structural analogues, both phosphonates have consistent chemical properties including high MW (573 and 299 respectively), very low log Kow(<-3 for both substances) and are highly soluble in water. The substances in question generally posses similar physico-chemical properties and are not readily biodegradable

The ammonium counterions of the substances are driving the toxicity of the properties under consideration and hence the read-across is proposed only data with DTPMP acid and sodium salts are available. Therefore, for the purpose of this assessment, read-across is considered valid.