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Toxicity to microorganisms

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Description of key information

No result is available for the registration substance. Two reliable studies, performed with a Na/H salt and a Ca/Mg salt of EDTMP, are available. The EC50 to WWTP micro-organisms was determined to be >100 mg/L as active acid, in two reliable studies conducted according to an appropriate test protocol, and in compliance with GLP. 

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
100 mg/L

Additional information

5.4% Inhibition and 0% inhibition respectively were seen at 100 mg/L loading (in terms of active acid), for an Na/H salt and a Ca/Mg salt of EDTMP; thus the EC50 is >100 mg/L. No NOEC or EC5 was derived by the report authors, however in view of the low level of inhibition (approximately 5%) seen at a loading of 100 mg/l, it is considered acceptable to interpret this concentration as an approximation of the EC5 for the purpose of PNEC derivation.

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 dissociatedto yield EDTMP and sodium ions. Hence some properties (measured or expressed in aqueous media) for a salt can be directly read across (with suitable mass correction) to the parent acid andvice versa(see CSR section 1 for mass correction values). In the present context the effect of the alkaline metal counter-ion (sodium) will not be significant and has been extensively discussed in the public literature. In biological systems and the environment, polyvalent metal ions will be present, and the phosphonate ions show very strong affinity to them.

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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