Tungsten trioxide

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.338 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.31 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.034 mg/L

Assessment factor:

100

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

79 mg/L

Assessment factor:

100

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

960 mg/kg sediment dw

Assessment factor:

10

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

96 mg/kg sediment dw

Assessment factor:

10

Extrapolation method:

equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

2.17 mg/kg soil dw

Assessment factor:

10

Extrapolation method:

assessment factor

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

General discussion

 

All PNECs derived are in concentration tungsten ion, as toxicity is expected to occur from the metal ion. The dissolution of tungsten from tungsten trioxide of 18.1% obtained from transformation/dissolution studies was used to estimate the equivalent tungsten concentration contributed from sodium tungstate and to determine if a PNEC needs to be estimated. A PNEC was developed when the tungsten equivalent dose was lower than the recommended limit dose (on a tungsten basis) of the respective study.

Conclusion on classification

Aquatic toxicity classification of inorganic metals and metal compounds is conducted by comparing transformation/dissolution (T/D) data for the substance, generated using the standard protocol (UN GHS, Annex 10) [see Table 5 in Section 1.3 for results] with toxicity data for the most soluble metal substance as described in the CLP technical guidance (section IV. 5 Application of classification criteria to metals and metal compounds) (EU, 2008). The T/D data is ideally tested at the pH at which the highest dissolution is expected, within the range defined by the test protocol (pH 5.5-8.5). Since inorganic tungsten substances have been demonstrated to have a higher T/D rate at pH 8.5 than pH 6, the data used for aquatic toxicity classification of tungsten trioxide was derived at pH 8.5 (24-hour, 7-, and 28-day T/D testing) (CANMET-MMSL, 2010). These T/D values were compared to the corresponding acute (31000 μg W/L, based on the E_rC50) and chronic (3380 μg W/L, based on the E_rC10) aquatic toxicity reference values derived from sodium tungstate testing of algae, as the most sensitive standard aquatic species for sodium tungstate. The results of this comparison demonstrate that tungsten trioxide does not classify for aquatic toxicity. The details of how this classification is derived are described in the table below.

Classification of tungsten trioxide using T/D data comparison to toxicity data according to the CLP technical guidance (European Chemicals Bureau, 2009)

Test type/ duration	T/D loading amount as WO3 (mg/L)	T/D results (μg W/L)	Toxicity reference value (μg W/L)	Comparison of T/D and toxicity values (μg W/L)	Aquatic Toxicity Classification Result
Screening test/ 24-hour	100	18150	Acute= 31000	18150<31000	Refer to full T/D test for classification.
Acute full test/ 7 days	1	607	Acute= 31000	607<31000	No Acute 1 classification
Acute full test/ 7 days	10	6030	Acute= 31000	6030<31000	No Acute 2 classification
Acute full test/ 7 days	100	62400	Acute= 31000	62400>31000	Acute 3 classification*
Chronic full test/ 28 days	1	627	Chronic=3380	627<3380	No Aquatic Classification

* Unless 28-day T/D data is < chronic toxicity reference value, then no acute or chronic classification.

The CLP classification scheme for evaluating aquatic toxicity of metals and metal compounds is the same as that used to classify metals and metal compounds under the Dangerous Substances Directive, with the exception of the name of the classifications (eg DSD cites R phrases; CLP uses acute and chronic categories). Although the DSD does not specifically cite the classification scheme for metals and metal compounds, the scheme was outlined in the ECB documents used in the classification of nickel metal (massive and powder). In addition, this classification scheme was used to evaluate aquatic toxicity of nickel metal and some copper compounds (ECB, 2001; ECB, 2005).