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Data were available for structural analogues, hence read across and molecular weight corrections have been applied, see also the read across justification in section 13.

A number of studies have been done to investigate short term effects on fish of HEDTA, including one study on a marine species (Scophthalmus maximus) (Schlumberger Dowell, 1999) and a number of studies on freshwater species. In the marine species, no mortalities were reported at the maximum exposure concentration of 738 mg/L, recalculated to H3HEDTA would give 592 mg/L.

Data from the freshwater studies reveal an LC50 of 808 mg/L in Lepomis macrochirus, 372 mg/L in Pimephales promelas and between 862 and 1861 mg/L in Leuciscus idus. These all indicate that acute toxicity to fish is low. Recalculation to H3HEDTA gives the worst case LC50 of 299 mg/L.

There are no available studies on the long term toxicity of exposure to HEDTA to Fish. Read-across to EDTA is considered appropriate based on similar ionisation potentials for EDTA and HEDTA. Long-term toxicity of CaNa2EDTA on freshwater fish was measured in an early life study with Brachydanio rerio (BASF, 2001). Results indicated a NOEC of greater than 25.7 mg/L after 35 days exposure, recalculated to H3HEDTA gives >= 18.5 mg/L.

Short term effects on aquatic invertebrates of HEDTA has been investigated in a marine species (Acartia Tonsa) and a freshwater species (Daphnia magna). Results in the marine species indicate a 48 hour LC50 of 2296 mg/L (1843 for H3HEDTA), while data from the freshwater species indicate a 48 hour LC50 of at least 192 mg/L, corresponding to 154 mg/L for H3HEDTA.

HEDTA is likely to show low long-term toxicity to aquatic invertebrates based on read-across to available studies on EDTA. A 21 -day study of toxicity of Na2EDTA on Daphnia magna in a reproduction test indicated a NOEC of 25 mg/L, corresponding to 20.5 mg/L H3HEDTA.

One study of low reliability is available regarding an assessment of toxicity to freshwater algae and aquatic plants, indicating an EC50 of 26 mg/L. The marked inhibitory effect of the structurally similar substance, Na4-EDTA, on the cell multiplication of Scenedesmus subspicatus was shown to be caused by the complexing of essential ferrous ions in the assay. This secondary effect was demonstrated using a modified test system without iron limitation when it was shown that the simultaneous application of equimolar concentrations of FeCl3*6H20 and EDTA up to 263.04 umol/L (100 mg/L Na4-EDTA) produced no inhibition of algal growth. The same is expected to occur with HEDTA. It is generally accepted that studies in which secondary effects have demonstrably affected outcome should not be used in the derivation of PNECs. Expressed as H3HEDTA this would be 72.6 mg/L.

The toxicity of HEDTA on microorganisms is considered likely to be low based on read-across to the structural analogue, EDTA, and one available study of low quality on HEDTA. The toxicity of Na2EDTA, a structural analogue of the substance, on microorganisms in an activated sludge resulted in an EC10 value after 30 minutes of > 500 mg/L. Similar low toxicity was observed in additional studies on activated sludge. Thus, inhibition of degradation activity of activated sludge is not anticipated.