Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Endpoints based on geometric mean measured values

Short term toxicity to Daphnia magna:

48 h EC50: >0.398 mg/L; OECD 202; Adachi, R. (2018)

Short term toxicity to Pseudokirchneriella subcapitata:

72 h ErC50: >0.2 mg/L; OECD 201; Inoue, H. (2019)

72 h NOEC: 0.025 mg/L; OECD 201; Inoue, H. (2019)

Additional information

Short-term toxicity studies were conducted in accordance with OECD guidelines for testing of algae and Daphnia magna; where the OECD 201and 202 methods were used, respectively. The substance contains inorganic and inorganic-metallic constituents. Inorganics are often highly insoluble, and metallic inorganics, when soluble, dissolve at varying rates and reach equilibrium at different stages dependent on the chemistry of the substance itself and the environmental medium in which it is exposed. 

 

Here, titanium and manganese are the metallic elements both of which dissolve to varying degrees. Although there are forms of these substances that are considered highly insoluble (OECD SIDS for manganese dioxide, 2007, and OECD SIDS for titanium dioxide, 2013), effects were noted below the solubility of the substance for the chronic algal endpoint. Therefore, the level of solubility and the effect it elicits is of ecological relevance and must be put into context using hazard and risk assessment processes when required. 

 

The undissolved and untransformed state(s) of metals are considered to not be bioavailable, and as such, no deleterious effects would be expected if transformation and dissolution have not occurred i.e. if they are not bioavailable, harmful exposure is not possible. Therefore, the bioavailability and subsequent toxic effects are directly correlated to the extent to which these substances transform or dissolve. 

 

The classification and labelling of metals and inorganic metal compounds is, therefore, based not only the observed toxicity (EC/LCx) but also the extent to which the substance can dissolve or transform. It is critical, therefore, to design aquatic toxicity studies to represent worst-case exposure scenarios by ensuring maximal dissolution/transformation is achieved before exposing the relevant test organisms. Determination of the time required to achieve maximal dissolution/transformation of the substance would be dictated by performing a transformation/dissolution test prior to designing and performing adequate (i.e. reliable and relevant) aquatic ecotoxicity studies. The results from these specifically designed aquatic ecotoxicity studies then allow the most appropriate and protective hazard and risk assessment. Thus, to fully interpret a data set for classification and labelling of a metal or inorganic metal compound, such as this, it is integral to have information from dissolution/transformation studies such as the transformation/dissolution medium (ISO 6341). This is particularly the case for those metal compounds that are not considered readily soluble (i.e. the solubility is less than the acute ecotoxicity reference value (ERV)). Here it would not be possible to classify the substance in accordance with the CLP regulation (Regulation (EC) No. 1272/2008) for either acute or chronic toxicity. 

 

This is the case for this substance, based on the currently presented data-set. Neither experimental test (OECD 201 and 202) led to acute toxicity at the level of dissolution tested (dissolution over 48-hours at a loading rate of 100 mg/L). Therefore, it was not possible to derive an acute ERV. According to Annex IV of Guidance on the Application of the CLP Criteria (v5.0, July 2017), classification of metals and inorganic metal compounds must be based upon both the 7-day transformation/dissolution study (at a loading rate of 1 mg/L) and the acute ERV. However, presently there are no data pertaining to the substance’s ability to transform or dissolve. Therefore, it is currently not possible to classify for acute toxicity. The Aquatic Acute Toxicity Classification of the substance is inconclusive. Additionally, as the 7-day transformation/dissolution data is not available, it is also not possible to determine if the aquatic ecotoxicity studies were suitably designed to maximize exposure concentrations.

 

For determining a chronic ERV, information on the NOEC of algae when exposed to the substance can be used. The chronic ERV can be set at 0.025 mg/L. Based on the currently available information, the substance is considered to be not readily soluble; the chronic toxicity value is also < 1 mg/L. However, there are no 28-day transformation/dissolution data available at 0.01, 0.1, or 1 mg/L loading rates. Therefore, it is not possible to classify using the chronic ERV. In this situation, the Guidance on the Application of the CLP criteria v5.0 (2017), suggests using the acute ERV in order to classify the chronic risk. However, the acute ERV is not available as no effects were seen in the current studies. Therefore, it is also not possible to classify for aquatic chronic effects using the acute toxicity values. Therefore, the Aquatic Chronic Toxicity Classification of the substance is also inconclusive. Also, as previously noted for the acute classification, it is also not possible to determine if the aquatic ecotoxicity studies were suitably designed to maximize exposure concentrations.

 

In order to appropriately classify the substance a full suite of transformation/dissolution studies should be conducted, i.e. a 24-hour Dissolution Screening test, a 7-d transformation/dissolution test and a 28-day transformation/dissolution test should be performed (in accordance with guidelines set out in Annex 10 of the globally harmonized system for classification and labelling). Any further acute/chronic aquatic ecotoxicity testing strategy and/or the classification will then be dictated by these results.

Aquatic Acute and Chronic Classification is currently inconclusive.