Chrome tungsten titanium buff rutile

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
According to Annex VII, Column 2, Section 9.1.2. of Regulation (EC) 1907/2006, the test for growth inhibition of aquatic plants 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 or the substance is unlikely to cross biological membranes”.

Chrome tungsten titanium buff rutile 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 transformation/dissolution data (Pardo Martinez, 2021) that indicate a very low release of pigment components at pH 6 and 8. Transformation/dissolution of chrome tungsten titanium buff rutile at a loading of 1 mg/L resulted in chromium and titanium concentrations < 0.25 µg/L, the corresponding LOD, and tungsten concentrations < 1 µg/L (< LOQ) after 7 and 28 days at pH 6 and pH 8, respectively. Thus, the rate and extent to which chrome tungsten titanium buff rutile produces soluble (bio)available ionic and other chromium-, titanium- and tungsten-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 chrome tungsten titanium buff rutile is expected to determine its behaviour and fate in the environment, and subsequently its potential for ecotoxicity.

Proprietary studies are not available for chrome tungsten titanium buff rutile. The poorly soluble substance chrome tungsten titanium buff rutile 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:

Regarding the acute toxicity, the ERVs of trivalent chromium, titanium and tungsten are above 1 mg/L, and a concern for short-term (acute) toxicity was 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 of chromium, titanium and tungsten ions and the fact that respective dissolved metal concentrations remained below the LOD (< 0.25 µg/L Cr; < 0.25 µg/L Ti) or LOQ (< 1 µg W/L) after 7-days T/D at pH 6 and 8, it can be concluded that the substance chrome tungsten titanium buff rutile is not sufficiently soluble to cause short-term toxicity at the level of the acute ERVs (expressed as EC50/LC50).

Regarding the long-term toxicity, the ERVs of trivalent chromium, titanium and tungsten are also above 1 mg/L, and a concern for long-term (chronic) toxicity was 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 of chromium, titanium and tungsten ions and the fact that the dissolved metal concentrations remained below the LOD (< 0.25 µg/L Cr; < 0.25 µg/L Ti) or LOQ (< 1 µg W/L)) after 28-days T/D at pH 6 and 8, it can be concluded that the substance chrome tungsten titanium buff rutile 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 chrome tungsten titanium buff rutile is poorly soluble and does not meet classification criteria for acute (short-term) and chronic (long-term) aquatic hazard.

Chrome tungsten titanium buff rutile is poorly soluble and unlikely to cross biological membranes. In accordance with Annex VII, Column 2, Section 9.1.2. of Regulation (EC) 1907/2006, testing for growth inhibition of aquatic plants is not necessary.