Chromium (III) oxide

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:

no hazard identified

Sediment (marine water)

Hazard assessment conclusion:

no hazard identified

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

A potential for endocrine disruption 0f chromium (III) substances was not identified in the EU RA on chromates (ECB, 2005), the Voluntary Risk Assessment of metallic Chromium and Trivalent Chromium Compounds (ICDA, 2008) and the CICAD 76 Inorganic Chromium (III) Compounds (WHO, 2009). Taken into account the poor solubility of chromium (III) oxide in environmental media, the natural abundance and speciation of chromium in freshwater, sediments and soil, the essentiality of chromium and the absence of reproductive effects in aquatic invertebrates and fish, chromium (III) oxide is also not expected to possess a potential for endocrine disruption in the environment.

For a documentation and justification of the read-across approach, please refer to the separate document attached to section 13, namely Read Across Assessment Report for chromium (III) oxide.

Conclusion on classification

The rate and extent to which chromium (III) oxide produces soluble (bio)available ionic and other chromium-bearing species in environmental media is limited. Further, the poor solubility of chromium (III) oxide is expected to determine its behaviour and fate in the environment, and subsequently its potential for ecotoxicity. Proprietary studies are not available for chromium (III) oxide (except for one short-term toxicity study on fish, see below). However, the fate and toxicity of chromium (III) oxide in the environment is evaluated by assessing the fate of its ecotoxicologically relevant moiety, the chromium (III) ion, and read-across to data available for other chromium (III) substances is applied.

Based on ECHA’s Guidance on the Application of the CLP Criteria (Version 5.0, July 2017), “the hazard classification schemes for metals and metal compounds are limited to the acute and long-term hazards posed by metals and metal compounds when they are available (i.e. exist as dissolved metal ions, for example, as M+ when present as M-NO3), and do not take into account exposures to metals and metal compounds that are not dissolved in the water column but may still be bioavailable, such as metals in food…”.

For poorly soluble metals and inorganic metal compounds that cannot be easily tested in aquatic toxicity test, the following is stated: ”where the compound is sufficiently poorly soluble that the levels dissolved following normal attempts at solubilisation do not exceed the available L(E)C50, it is the rate and extent of transformation, which must be considered.”

The solubility of chromium (III) oxide in environmental media is low. In a short-term transformation/dissolution test with a loading of 100 mg/L, a dissolved Cr concentration of 0.11 microg/L Cr was determined at pH 6 after 7 days whereas dissolved Cr concentrations were below the LOD (< 1 microg/L) at pH 8 (Hedberg and Wallinder, 2012). Transformation/dissolution at a loading of 1 mg/L resulted in dissolved chromium concentrations below the LOD (< 0.01 microg/L) at pH 6 after 7 days and 28 days. Furthermore, chromium (VI) could not be detected during the test (< 0.01 microg/L). In sum, chromium (III) oxide can be considered environmentally and biologically inert during short- and long-term exposure.

The following acute and chronic aquatic toxicity data were derived in aquatic toxicity tests with soluble chromium (III) substances (including chromium (III) chloride, chromium (III) nitrate, chromium (III) sulphate, chromium hydroxide sulphate and chromium potassium sulfate).

Acute (short-term) aquatic hazard: Acute aquatic toxicity data of chromium (III) substances are available for three trophic levels (algae, invertebrates and fish):

A 72-h ErC50 > 0.148 mg Cr(III)/L was reported for the growth of the freshwater alga Desmodesmus subspicatus.

The reliable 48-h LC/EC50 values of 2 freshwater aquatic invertebrate species (D. magna, C. dubia) range from 3.71 – 14.1 mg Cr(III)/L.

The acute LC50 values for soluble chromium (III) substances range from 4.0 – 40.1 mg Cr(III)/L for 4 freshwater fish species.

Further, in an acute fish toxicity study with the poorly soluble chromium (III) oxide, effects were not observed at the highest nominal test concentration of 10,000 mg/L corresponding to > 1.0 microg dissolved Cr/L (> 2.9 microg dissolved chromium (III) oxide /L).

In accordance with ECHA Guidance on the Application of the CLP Criteria (V 5.0, July 2017), “A poorly soluble substance is evaluated for classification by comparing the dissolved metal ion level resulting from the T/Dp at 7 d, at a loading rate of 1 mg/l with the acute ERV as determined for the (soluble) metal ion.”

The release of chromium from chromium (III) oxide at a loading of 1 mg/L after 7 days at pH 6 (i.e. the pH that maximizes the dissolution) results in concentrations < 0.01 microg dissolved Cr/L and are thus well below the lowest reliable acute effect concentration (3.71 mg/L) The dissolution level of the poorly soluble chromium (III) oxide from the 7 d T/Dp at 1 mg loading at pH 6 is lower than the acute ERV of the soluble chromium (III) ion, thereby not resulting in an acute classification. Thus, in accordance with Figure IV.4 “Classification strategy for determining acute aquatic hazard for metal compounds” of ECHA Guidance on the Application of the CLP Criteria (V 5.0, July 2017) and section 4.1.2.10.2. of Regulation (EC) No 1272/2008, classification for acute (short-term) aquatic hazard is not required for chromium (III) oxide.

 

Long-term (chronic) aquatic hazard: Long-term aquatic toxicity data of chromium (III) substances are available for three trophic levels (algae, invertebrates, fish):

A 72 -h ErC10 of 2.0 µg Cr(III)/L was reported for the growth rate inhibition of the freshwater alga Desmodesmus subspicatus.

The 21-d NOEC for the freshwater invertebrate Daphnia magna was≥0.0144 mg Cr(III)/L.

The chronic 30-d NOEC for dissolved chromium (III) was ≥ 0.018 mg Cr/L for the freshwater fish Danio rerio.

Chromium (III) oxide is evaluated for classification by comparing the dissolved metal ion level resulting from the T/Dp at 28 d, at a loading rate of 1 mg/l with the chronic ERV as determined for the (soluble) chromium (III) ion. The release of chromium from chromium (III) oxide at a loading of 1 mg/L after 28 days at pH 6 (i.e. the pH that maximizes the dissolution) results in concentrations < 0.01 microg dissolved Cr/L and are thus well below the lowest chronic effect concentration (2.0microg/L for algae). Hence, the dissolution level of the poorly soluble chromium (III) oxide from the 28 d T/Dp at 1 mg loading at pH 6 is lower than the chronic ERV of the soluble chromium (III) ion, thereby not resulting in a long-term (chronic) classification. Thus, in accordance with Figure IV.5 „Classification strategy for determining long-term aquatic hazard for metal compounds“ of ECHA Guidance on the Application of the CLP Criteria (V 5.0, July 2017) and section 4.1.2.10.2. of Regulation (EC) No 1272/2008, classification for long-term (chronic) aquatic hazard is not required for chromium (III) oxide.

In sum, chromium (III) oxide does not meet classification criteria of an acute or long-term aquatic hazard of Regulation (EC) No 1272/2008.