Tungsten

Endpoint summary

Description of key information

Toxicity to Soil Macroorganisms: No sufficiently reliable studies were identified for tungsten metal toxicity in plants; therefore, read-across to sodium tungstate was used. The 56-day NOEC for earthworms (Eisenia fetida) found in a test conducted according to OECD 222, under GLP standards, and with analytical verification of the test concentrations was ≥1000 mg sodium tungstate/kg soil dw (586 mg W/kg). Other studies withEisenia fetidawere not considered for the risk characterisation, as they were found to be less reliable.

Toxicity to Terrestrial Plants: No sufficiently reliable studies were identified for tungsten metal toxicity in plants; therefore, read-across to sodium tungstate was used. In a Seedling Emergence and Seedling Growth Test using Avena sativa, Raphanus sativus and Lactuca sativa and testing sodium tungstate, Lactuca sativa (lettuce) was found to be the most sensitive species with an identified NOEC of 37 mg/kg soil d. w. sodium tungstate (nominal) (approximately 22 mg W/kg soil) based on: % Emergence, Individual Shoot Height, and Individual Shoot Weight.

Toxicity to Soil Microorganisms: No sufficiently reliable studies were identified for tungsten metal toxicity in plants; therefore, read-across to sodium tungstate was used. In both a Carbon and a Nitrogen Transformation Test using sodium tungstate the 28-day EC50 was found to be > 1000 mg sodium tungstate/kg soil dw (approximately  586 mg W/kg soil dw).

Toxicity to Birds: An LD50 for mallards orally dosed with tungsten-polymer shot was determined.  Results indicated that tungsten-polymer shot orally administered to mallards did not adversely affect them during a 30-day trial and an LD50 of  > 3.07 g tungsten/kg bw was identified (Kelly et al, 1998).   In a separate study in which mallards were dosed with tungsten-nylon pellets once per month over a period 150 days (days 0, 30, 60, 90, 120 and 150),  the NOAEL determined was ≥ 1.21 g tungsten/kg bodyweight per month.  This study revealed that mallard ducks did not have deleterious health effects during the 150-day trial based on mortality, body weights, organ weights, and histology of the liver and kidneys (Mitchell et al, 2001a) or hematological effects (Mitchell et al, 2001b) compared to the control. There were no significant differences in egg production and fertility and hatchability of eggs from tungsten-polymer-dosed ducks compared to control ducks. There was no evidence of differences in percent survivability and body weight of ducklings from tungsten-iron and tungsten-polymer mallards compared to ducklings from control ducks (Mitchell et al, 2001c).  Ingested tungsten does not seem to adversely effect mallards after chronic exposures.