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Based on nominal concentrations, the 3 -h EC50, EC10 and NOEC without ATU (nitrification inhibitor) were determined to be > 648 mg Pt L-1, 648 mg Pt L-1, and 207 mg Pt L-1, respectively. The 3 -h EC50 and EC10 with ATU were both determined to be > 648 mg Pt L-1, and the relative NOEC was determined to be 648 mg Pt L-1. 

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An activated sludge respiration inhibition test was conducted with dihydrogen hexahydroxyplatinate following OECD guideline 209 and EU Method C.11 (Muckle 2014). Three experiments were performed, including a range-finding test, a limit test using the concentration of 1000 mg L-1, and a third test using the concentrations of 320 and 100 mg L-1. Two test series were carried out, with and without the nitrification inhibitor N- allylthiourea (ATU) to discern between inhibition of nitrificators and inhibition of the total population. A positive control was used, and all validity criteria were met. Based on nominal concentrations, the 3-h EC50, EC10 and NOEC without ATU were determined to be > 1000 mg test item L-1 (> 648 mg Pt L-1), 1000 mg test item L-1 (648 mg Pt L-1), and 320 mg test item L-1 (207 mg Pt L-1), respectively. The 3 -h EC50 and EC10 with ATU were both determined to be > 1000 mg test item L-1 (> 648 mg Pt L-1), and the relative NOEC was determined to be 1000 mg test item L-1 (648 mg Pt L-1).

 

For platinum(IV) substances there is some evidence that substances containing a chloro ligand are more toxic than those without a chloro ligand. For this reason, for substances without a chloro ligand, read across for REACH endpoints and for classification purposes is only conducted with other substances that do not contain a chloro ligand. However, for risk assessment purposes measured platinum concentrations in the environment only allow assessment of total platinum concentrations and do not differentiate between the form of the platinum in the environment. The PNEC for platinum(IV) substances is therefore based on pooled ecotoxicity data for all platinum(IV) substances, regardless of the ligands, and is based on the most toxic substance. For platinum(IV) substances the most toxic substance is hexachloroplatinic acid and the PNECs for platinum(IV) substances are therefore based on data for this substance. The key study driving the PNEC STP for platinum(IV) substances is an activated sludge respiration inhibition study for hexachloroplatinic acid.

 

An activated sludge respiration inhibition test was conducted with hexachloroplatinic acid following OECD guideline 209 and EU Method C.11 (Muckle 2015). Two test series were carried out, with and without the nitrification inhibitor N- allylthiourea (ATU) to discern between inhibition of nitrificators and inhibition of the total population. Based on a range-finding test where significant inhibition was observed, two additional tests were performed, where 5 concentrations ranging from 1 to 320 mg test item L-1 were tested with and without ATU, respectively. A positive control was used, and all validity criteria were met. Based on nominal concentrations, the 3-h EC50, EC10 and NOEC values without ATU were determined to be 103 mg test item L-1 (40.33 mg Pt L-1), 6.0 mg test item L-1 (2.35 mg Pt L-1), and 3.2 mg test item L-1 (1.26 mg Pt L-1), respectively. The 3 -h EC50, EC10 and NOEC values with ATU were determined to be 83 mg test item L-1 (32.49 mg Pt L-1), 8.2 mg test item L-1 (3.21 mg Pt L-1), and 10 mg test item L-1 (3.92 mg Pt L-1), respectively.