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Toxicity to terrestrial arthropods

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Description of key information

A total of 10 topsoils with contrasting properties that may affect the toxicity of Mo in soil were used for testing a toxicity assay with the arthropod invertebrate, Folsomia candida, after spiking with sodium molybdate.  In addition, an OECD artificial soil was also tested.
The arthropod toxicity assay resulted in only 3 individual high quality NOEC/EC10 selected for PNEC derivation. In the other 8 soils, no toxic effect was observed at the largest dose tested. The bounded NOEC/EC10 values ranged from 37,9 to 1865 mg added Mo/kg dry weight soil.
Additionally, 3 soils were aged outdoors after spiking with sodium molybdate. After 6 and 11 months, subsamples were collected and the same ecotoxicity tests as above were conducted on these soils. The ageing data for the arthropodcould not be used for deriving a Leaching/Ageing factor given that already in the spiked soils, no effects were observed.

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Additional information

For the arthropod invertebrate toxicity assay, Folsomia candida was used as a test species. Only 3 soils resulted in reliable, bounded NOEC values. In all 8 other soils, no toxic effect was observed at the largest dose tested (unbounded NOEC values between >2628 and 3395 mg added Mo/kg dw. the reliable NOEC/EC10 values taken forward for the PNEC derivation ranged from 37.9 to 1865 mg added Mo/kg dw. All data are based on added measured Mo concentrations in soil.

Not much could be concluded regarding the results of the 3 aged soils given that already in the spiked soils, no effects were observed. In one of the 3 aged soils, an effect was noted, although at a concentration greater than the unbounded NOEC in the spiked soil.