Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Soil macroorganisms:

Tungsten carbide was not tested for toxicity to soil macro-organisms, and read across to sodium tungstate was used for this endpoint. In an earthworm reproduction test using Eisenia fetidaand testing sodium tungstate, the NOEC was found to be greater than or equal to the highest concentration tested (≥1000 mg sodium tungstate/L, or approximately 586 mg W/L).

Terrestrial plants:

Tungsten carbide was not tested for toxicity to terrestrial plants, and read across to sodium tungstate was used for this endpoint. In a Seedling Emergence and Seedling Growth TestusingAvena sativa,Raphanus sativusandLactuca sativaand testing sodium tungstate, Lactuca sativa(lettuce) was found to be the most sensitive species, with an identified NOEC of37 mg/kg soil d.w. sodium tungstate (nominal) (approximately 22 mg W/L)based on: Individual Shoot Weight.

Soil microorganisms:

In addiiton, tungsten carbide was not tested for toxicity to soil micro-organisms and read-across to sodium tungstate was used for this endpoint. In both a Carbon and a Nitrogen Transformation Test using sodium tungstate the 28-day EC50 was found to be > 1000 mg/kg soil d.w. (sodium tungstate concentration) (nominal) (approximately 586 mg W/kg).

Birds:

Several older studies on chicken species were identified in which the birds were fed varying amounts of tungsten, in the form of sodium tungstate in their diets. The NOAELs identified from these studies ranged from approximately 45-500 mg tungsten/kg, depending on which endpoints were examined in each study. However, none of these studies were conducted with standard methodology and they were deemed to be less than reliable.

Additional information

Due to similar or lower transformation/dissolution results for tungsten carbide (the target substance) than sodium tungstate (the source substance), the resulting toxicity potential would also be expected to be similar or lower, so read-across is appropriate. In addition, read-across is justified because the classification and labeling is the same or less severe for the target substance PBT/vPvB profile is the same. Finally, the dose descriptors are, or are expected to be, sufficiently similar or higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read across approach.