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In accordance with Column 2 of REACH Annex IX, there is no need to further investigate the effects of this substance in a long-term terrestrial toxicity to higher plants study because:

• The substance is involatile and highly adsorbing and low toxicity was observed in the available pelagic organism and aquatic microorganism tests, and there is no reason to expect effects in the terrestrial compartment that were not expressed in the aquatic compartment. 

• Based on the aquatic data set, the most sensitive relevant trophic level is invertebrates. A long-term earthworm reproduction test for a closely related substance within the HEDP category is already available, and low toxicity was observed (NOEC 500 mg/kg active acid, Noack, 2014).

• The soil hazard category 3 (ECHA guidance part R7(c) table R.7.11-2) applies for this substance. According to the specified approach for soil hazard category 3 substances, if PEC/PNEC screen <1 and there is no indication of risk from confirmatory long-term soil toxicity testing then no further toxicity testing for soil organisms is necessary, as has been demonstrated for this substance.

• The phosphonate ligand binds strongly and irreversibly to various minerals present in soil and so bioavailability to soil organisms is extremely limited.

The terrestrial chemical safety assessment has been conducted using the Equilibrium Partitioning method (EQPM).

It is recognised that the aquatic PNEC used in the EQPM does not take into account any indicator for effects in aquatic microorganisms. However, a reliable study of the effects on anaerobic sewage treatment plant micro-organisms with HEDP-H records a lack of effects on bio-gas production up to at least 200 mg active acid/l (Henkel, 1972). A study with HEDP-xNa determined an IC0 value of >250 mg/l for the effects on bioluminescence with the bacterium Photobacterium phosphoreum (Grohmann and Horstman, 1989). Another study with HEDP-H, on aerobic sewage treatment plant micro-organisms, indicates a lack effects on MBAS reduction of up to 300 mg active acid/l after 53 days exposure in a simulation study (Henkel, 1972). These studies demonstrate the low toxicity of HEDP and its salts to micro-organisms. See Section 6.1.7 for further details.

These results show a similar level of effect to that observed in the lowest reliable short-term aquatic toxicity study with fish, where a 96-h LC50 value of 195 mg active acid/L with Salmo gairdneri was determined (EG&G, 1976).

The data on long-term ecotoxicity to fish and invertebrates also suggest that aquatic microorganisms are comparatively less sensitive, where the lowest reliable long-term toxicity NOEC value was observed with invertebrates at 6.25 mg active acid/L.

Therefore it is unlikely that the PNECterrestrial based on aquatic ecotoxicity test results would not be protective for terrestrial microorganisms.

The chemical safety assessment using EQPM does not suggest any unacceptable risks for the terrestrial compartment.