Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

A 28-day EC10 value of >1000 mg active acid/kg dry weight and a 28-day EC50 of >1000 mg active acid/kg dry weight have been determined for the effects of the test substance on the nitrogen formation rate of soil microorganisms.

A 56-day EC10 value of 543 mg active acid/kg dry weight and a 28-day NOEC value of 556 mg/kg dry weight have been determined for the effects of the test substance on mortality and reproduction of the earthworm, Eisenia fetida.

Both studies are currently available in draft-format only, but the effect concentration values are not expected to change in the final study reports. These studies were assigned reliability 1 and were conducted in accordance with OECD test guidelines and GLP.

Due to its high adsorption and low toxicity to aquatic organisms, HMDTMP was assigned to soil hazard category 3 and a PNECscreen was conducted, based on the equilibrium partitioning method (PEC * 10 / PNECscreen). Testing for toxicity to terrestrial organisms has been carried out with two representing two taxonomic groups and two trophic levels (decomposers and consumers): earthworms and soil microorganisms.The PNECs based on terrestrial ecotoxicity studies is more conservative and asthe terrestrial RCRs are < 1, no further toxicity testing of soil organismsis currently considered to be necessary.

Additional information

The HMDTMP anion can be considered fully dissociated from its sodium cation when in dilute solution.

Water and sodium cations present in the test material would not be expected to contribute significantly to toxicity at the concentrations used. Thus, the active ingredient (a.i.) is the acid form, HMDTMP-H. Test concentrations and test results are presented throughout this report in terms of the active acid equivalent mass (or concentration), HMDTMP-H, expressed as mg a.i./kg soil dry weight.

HMDTMP and its salts are highly adsorbing to soil and soil mineral substrates. The nature of the adsorption is believed to be primarily due to interaction with inorganic substrate or generalised surface interactions. High adsorption is consistent with similar behaviour seen for the analogues ATMP and DTPMP, and other common complexing agents such as EDTA. By reference to findings with other similar substances, the binding occurs very rapidly and is effectively irreversible.