Tungsten dioxide

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

no hazard identified

Marine water

Hazard assessment conclusion:

no hazard identified

STP

Hazard assessment conclusion:

no hazard identified

Sediment (freshwater)

Hazard assessment conclusion:

insufficient hazard data available (further information necessary)

Sediment (marine water)

Hazard assessment conclusion:

insufficient hazard data available (further information necessary)

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

no hazard identified

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

All PNECs presented herein are expressed in terms of the concentration of tungsten ion, as toxicity is expected to occur from the metal ion. The dissolution of tungsten from tungsten dioxide of 0.78% obtained from 100 mg/L loading (pH 8.5) at 24 hours 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 ecotoxicity 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 3 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 than pH 6, the data used for aquatic toxicity classification of tungsten dioxide was derived at pH 8 (24-hour, 7-, and 28- day T/D testing) (CIMM, 2012). These T/D values were compared to the corresponding acute (31000 μg W/L, based on the ErC50) and chronic (3830 μg W/L, based on the ErC10) 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 dioxide does not classify for aquatic toxicity (see table below).  

  

Classification of tungsten dioxide 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 WO2[mg/L]	T/D results [µg W/L] pH 8	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	72	Acute = 31000	72 < 31000	Refer to full T/D test for classification
Acute full test / 7-days	1	33	Acute = 31000	33 < 31000	No classification for acute hazards
Acute full test / 7-days	10	239	Acute = 31000	239 < 31000	No Chronic 2 classification
Acute full test / 7-days	100	4225	Acute = 31000	4225 < 31000	No Chronic 3 classification
Chronic full test / 28-days	1	106	Chronic = 3830	106 < 3830	No Chronic 2 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).