Diarsenic triselenide

Ecotoxicological Summary

Conclusion on classification

The environmental classification is based on the environmental classification of the released consitutents (ions). The Transformation dissolution (T/D) test (OECD 29) is a test that determines the rate and extent to which metals and sparingly-soluble metal compounds can produce soluble available metal ions in aqueous media (I.e. freely available metal ion = toxic entity).The measured dissolved concentration of the individual metal of the complex metal compound/mixtures are compared to their respective Environmental Reference Value (ERV); exceeding one of the individual acute/chronic ERVs, triggers a respective acute/chronic classification of the complex metal compound under consideration.

Both the (marketed) full lenses as the milled test item (< 1mm) were tested.

Milled test item:

At a loading of 1 mg/L Gasir 5 to the OECD 203 (ISO 6341) standard medium at pH 8, for arsenic, average values of 9.53 μg/L As (CV=20%) and 22.7 μg/L As (CV=12%) were found at the 7 days and 28 days endpoints, respectively. Based on the specific surface area ofGasir 5(i.e. 1.54 m2/g test item), an arsenic release per surface of 6.2 mg/m2 and 15 mg/m2 were calculated at the 7 days and 28 days endpoints, respectively. Based on the average arsenic content in the test item (38.1%) and the average dissolved arsenic concentrations in the test solution, an arsenic release of 2.5% and 6.0% could be calculated at the 7 days and 28 days extraction endpoints, respectively. A second-order kinetic equation can describe the transformation/dissolution characteristics of Gasir 5 for arsenic. For selenium average values of 1.46 μg/L Se (CV=9%) and 7.79 μg/L Se (CV=13%) were measured at the 7 days and 28 days endpoints, respectively. Based on the specific surface area ofGasir 5(i.e. 1.54 m2/g test item), a selenium release per surface of 0.95 mg/m2 and 5.1 mg/m2 were calculated at the 7 days and 28 days endpoints, respectively. Based on the average selenium content in the test item (59.8%) and the average dissolved selenium concentrations in the test solution, a selenium release of 0.24% and 1.3% could be calculated at the 7 days and 28 days extraction endpoints, respectively. The transformation/dissolution characteristics ofGasir 5for selenium can be described by a linear kinetic equation.

Full lenses

At a loading of 300 mg/LGasir 5(surface equivalent) to the OECD 203 (ISO 6341) standard medium at pH 8, for arsenic, average values of 2.37 μg/L As (CV=16%) and 3.28 μg/L As (CV=8%) were found at the 7 days and 28 days endpoints, respectively. Based on the exposed surface area of aGasir 5lens (i.e. 734.2 mm2/1884 mL), an arsenic release per surface of 6.1 mg/m2 and 8.4 mg/m2 could be calculated at the 7 days and 28 days extraction endpoints, respectively.

For selenium average values of 0.11 μg/L Se (CV=17%) and 0.39 μg/L Se (CV=17%) were measured at the 7 days and 28 days endpoints, respectively. Based on the exposed surface area of aGasir 5lens (i.e. 734.2 mm2/1884 mL), a selenium release per surface of 0.28 mg/m2 and 1.0 mg/m2 could be calculated at the 7 days and 28 days extraction endpoints, respectively.

These results can be compared with the acute and chronic ecotoxicity reference values (ERVs) at the corresponding pH of arsenic and selenium in order to get information about the toxicity of the test item in aqueous medium and to classify the test item according to the EU-CLP and UN-Globally Harmonized System.

Since the test item is placed on the market as massive (>1 mm materials), it is possible to correct for the exposed surface (using the results of the N-BET analysis).

Short term or Acute toxicity

ERV for As is 430 ug/L and ERV for Se is 550 ug/L.

The additivity method gives the following:

• 9.53 / 430 + 1.46 / 550 < 1 at 1 mg/L (milled test item)
• 2.37 / 430 + 0.11 / 550 < 1 at 300 mg/L (full lenses), also < 1 at 1 mg/L

Long term or Chronic toxicity

ERV for As is 40 ug/L and ERV for Se is 21 ug/L.

The additivity method gives the following:

• 22.7 / 40 + 7.79 / 21 < 1 at 1 mg/L (milled test item), also < 1 at 0.1 mg/L
• 3.28 / 40 + 0.39 / 21 < 1 at 300 mg/L (full lenses), also < 1 at 0.1 mg/L

In conclusion, acute and chronic metal dissolution based on OECD 29 is lower than the respective environmental reference values. Consequently, no acute or chronic aquatic environmental classification is necessary.