Chromium tin calcium silicon sphene

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance is highly insoluble in water, hence indicating that aquatic toxicity is unlikely to occur

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
According to Annex VIII, Column 2, Section 9.1.4. of Regulation (EC) 1907/2006, the test for activated sludge respiration inhibition does not need to be conducted “if there are mitigating factors indicating that aquatic toxicity is unlikely to occur, for instance if the substance is highly insoluble in water”.

Chromium tin calcium silicon sphene can be considered environmentally and biologically inert due to the characteristics of the synthetic process (calcination at a high temperature of approximately 1000°C), rendering the substance to be of a unique, stable crystalline structure in which all atoms are tightly bound and not prone to dissolution in environmental and physiological media. This assumption is supported by available transformation/dissolution data (Pardo Martinez, 2013) that indicate a very low release of pigment components at pH 8. Transformation/dissolution of chromium tin calcium silicon sphene (24-screening test according to OECD Series 29) at a loading of 100 mg/L and pH 6 and 8 resulted in chromium concentrations below the LOD (< 0.5 µg/L) while tin concentrations of 5.4 and 11.5 µg Sn/L were measured, respectively. Thus, metal release from the pigment is maximised at pH 8. The dissolved chromium concentrations remained also below the LOD (< 0.5 µg/L) after 7 and 28 days in the T/D test with 1 mg/L loading at pH 8 while dissolved tin concentrations amount to 2.2 and 3.8 µg Sn/L, respectively. Calcium and silicon were not considered in the T/D assessment since they do not have an ecotoxic potential as confirmed by the absence of respective ecotoxicity reference values in the Metals classification tool (MeClas) database (see also OECD 2002 and 2004). Thus, the rate and extent to which chromium tin calcium silicon sphene produces soluble (bio)available ionic and other calcium-, chromium-, silicon- and tin-bearing species in environmental media is limited. Hence, the pigment can be considered as environmentally and biologically inert during short- and long-term exposure. The poor solubility of chromium tin calcium silicon sphene is expected to determine its behaviour and fate in the environment, and subsequently its potential for ecotoxicity.

Proprietary studies are not available for chromium tin calcium silicon sphene. The poorly soluble substance chromium tin calcium silicon sphene is evaluated by comparing the dissolved metal ion levels resulting from the transformation/dissolution test after 7 and 28 days at a loading rate of 1 mg/L with the lowest acute and chronic ecotoxicity reference values (ERVs) as determined for the (soluble) metal ions. The acute and chronic ERVs are based on the lowest EC50/LC50 or NOEC/EC10 values for algae, invertebrates and fish, respectively, and were obtained from the Metals classification tool (MeClas) database as follows:

Acute ERVs for calcium and silicon are not available since a concern for short-term toxicity was not identified, respectively (see also OECD, 2002 and 2004). For trivalent chromium and tin ions, the acute ERVs are above 1 mg/L (>100 mg Cr3+/L; 9.8 mg Sn/L) and a concern for short-term (acute) toxicity was also not identified (no classification). According to ECHA Guidance on the Application of the CLP Criteria (Version 5.0, July 2017), “Where the acute ERV for the metal ions of concern is greater than 1 mg/L the metals need not be considered further in the classification scheme for acute hazard.” Due to the lack of an acute aquatic hazard potential for calcium, chromium, silicon and tin ions and the fact that (after 7 days T/D at pH 8 and a loading of 1 mg/L) dissolved concentrations of chromium remained below the LOD (< 0.5 µg/L) and the tin concentration amounts to 2.2 µg Sn/L and is well below the lowest acute ERV of 9.8 mg Sn/L, it can be concluded that the substance chromium tin calcium silicon sphene is not sufficiently soluble to cause short-term toxicity at the level of the acute ERVs (expressed as EC50/LC50).

Regarding long-term toxicity, chronic ERVs for calcium and silicon are not available since a concern for long-term toxicity of calcium and silicon ions was not identified (see also OECD, 2002 and 2004). For trivalent chromium and tin ions, the chronic ERVs are above 1 mg/L, and a concern for long-term (chronic) toxicity was also not identified (no classification). According to ECHA Guidance on the Application of the CLP Criteria (Version 5.0, July 2017), ”Where the chronic ERV for the metal ions of concern corrected for the molecular weight of the compound (further called as chronic ERV compound) is greater than 1 mg/L, the metal compounds need not to be considered further in the classification scheme for long-term hazard.” Due to the lack of a chronic aquatic hazard potential for calcium, chromium, silicon and tin ions and the fact that (after 28 days T/D at pH 8 and a loading of 1 mg/L) dissolved concentrations of chromium remained below the LOD (< 0.5 µg/L) and tin concentration amount to 3.8 µg Sn/L whereas the respective chronic ERV is above 1 mg/L, it can be concluded that the substance chromium tin calcium silicon sphene is not sufficiently soluble to cause long-term toxicity at the level of the chronic ERVs (expressed as NOEC/EC10).

In accordance with Figure IV.4 “Classification strategy for determining acute aquatic hazard for metal compounds” and Figure IV.5 „Classification strategy for determining long-term aquatic hazard for metal compounds “of ECHA Guidance on the Application of the CLP Criteria (Version 5.0, July 2017) and section 4.1.2.10.2. of Regulation (EC) No 1272/2008, the substance chromium tin calcium silicon sphene is poorly soluble and does not meet classification criteria for acute (short-term) and chronic (long-term) aquatic hazard.

Chromium tin calcium silicon sphene is poorly soluble. Based on the poor solubility and the corresponding lack of a toxic potential, inhibition of activated sludge respiration or toxicity to microorganisms is not expected. In accordance with Annex VIII, Column 2, Section 9.1.4. of Regulation (EC) 1907/2006, the test for activated sludge respiration inhibition is not necessary.

References:

OECD (2002) SIDS Initial Assessment Report Calcium Chloride CAS N°:10043-52-4. SIAM 15, 22-25 October 2002.

OECD (2004) SIDS Initial Assessment Profile Silicon dioxide, Silicic acid, aluminum sodium salt, Silicic acid, calcium salt. SIAM 19, 19-22 October 2004.

Cross-reference

Reason / purpose for cross-reference:

data waiving: supporting information