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EC number: 231-143-9 | CAS number: 7440-33-7
- The ASR system provided the oxygen consumption/depletion curve as a plot of the dissolved oxygen concentration (mg O2/L) versus time (seconds). The analyst selected the appropriate start and end times between which the oxygen depletion curve was linear, and the ASR system automatically calculated the oxygen consumption rate (respiration rate) and expressed these rates as mg O2L-1hr-1.
No microorganisms toxicity data of sufficient quality are available for tungsten metal (target substance). However, microorganisms toxicity data are available for sodium tungstate (source substance), which will be used for reading across. Due to lower water solubility and lower toxicity for the target substance compared to the source substance, the resulting read across from the source substance to the target substance is appropriate as a conservative estimate of potential toxicity for this endpoint. In addition, read across is appropriate because the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the read-across category approach included in the Category section of this IUCLID submission and/or as an Annex in the CSR.
A 30-min. EC50 of >1000 mg sodium tungstate/L (586 mg tungsten/L) was found in a OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test) using domestic activated sludge.
Due to lower transformation/dissolution results for tungsten metal (the target substance) than sodium tungstate (the source substance), the resulting toxicity potential would also be expected to be lower, so read-across is appropriate. In addition, read-across is justified because the classification and labelling is the less severe for the target substance and the PBT/vPvB profile is the same. Finally, the dose descriptor for the target substance is expected to be sufficiently lower than the source chemical, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read across approach.
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