Dichromium nitride

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

Conclusion on classification

Dichromium nitride is a poorly soluble inorganic substance. In accordance with ECHA Guidance on the Application of the CLP Criteria (V 5.0, July 2017), “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 release of chromium in environmental media at pH 6 and 8 was determined in an OECD transformation/dissolution test (Brouwers, 2018) and resulted in dissolved trivalent chromium concentrations that were below the LOD (0.5 microg/L) after 7 and 28 days, respectively. Furthermore, dissolved chromium (VI) was not detected (< LOD of 0.05 microg/L) in any solution (pH 6 and pH 8) at any time.

Acute and chronic aquatic toxicity data of inorganic chromium (III) substances were reviewed and summarised in the CICAD for trivalent chromium substances (WHO, 2009). The therein reported effect concentrations originate from published studies and were generated in aquatic toxicity tests with soluble chromium substances (including chromium (III) chloride, chromium (III) nitrate, and chromium potassium sulfate).

Acute (short-term) aquatic hazard:

Acute aquatic toxicity data of soluble chromium (III) substances are available for three trophic levels (algae, invertebrates and fish).

96-h EC₅₀ values ranging from 0.3 - 0.4 mg chromium(III)/L were reported for the growth and biomass of the freshwater alga (Selenastrum capricornutum) whereas a 96-h EC₅₀ of 2 mg chromium(III)/L based on growth was reported for a marine diatom (Ditylum brightwellii).

The acute LC50 values of 15 freshwater invertebrate species range from 0.1 - 442 mg/L and range from 10 to 100 mg/L for five marine invertebrates.

The 96-h LC50 values of 12 freshwater fish species range from 3.3 - 151 mg/L and for two marine species from 31.5 – 53 mg/L.

In accordance withECHA 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 TDp at 7d, at a loading rate of 1 mg/l with the acute ERV as determined for the (soluble) metal ion.”

The release of chromium from dichromium nitride at a loading of 1 mg/L at pH 6 and pH 8 after 7 days results in concentrations < 0.5 microgdissolved Cr/L and are thus well below the lowest acute effect concentration (0.1 mg/L) reported by WHO (2009). The dissolution level of the poorly soluble metal compound from the 7/d T/Dp at 1 mg loading for both pH levels is lower than the acute ERV of the soluble metal 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 dichromium nitride.

Long-term (chronic) aquatic hazard:

Chronic aquatic toxicity data of soluble chromium (III) substances are available for two trophic levels (invertebrates and fish).

A NOEC/EC10 was not reported for algae or aquatic plants. However, based on short-term LC/EC50 values, algae do not appear to be the most sensitive taxonomic group. A 14- to 21-d EC50 (biomass) of 0.6. mg/L was reported for Selenastrum capricornutum.

A 21-d (NOEC) (reproduction) of 0.7 mg/L and two NOEC (life cycle) values of 0.047 mg/L and 0.129 mg/L were reported for Daphnia magna whereas a 293-d NOEC (behaviour and reproduction) of 50.4 mg/L is listed for the (marine) polychaete (Neanthes arenaceodentata). The 72-d NOEC (survival) of 0.05 mg/L was derived for rainbow trout (Oncorhynchus mykiss) (WHO, 2009).

The release of chromium from dichromium nitride at a loading of 1 mg/L at pH 6 and pH 8 after 28 days results in concentrations < 0.5 microg dissolved Cr/L and are thus well below the lowest chronic effect concentration (0.047 mg/L) reported by WHO (2009). 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 (acute) aquatic hazard is not required for dichromium nitride.

The conclusion on a lack of an aquatic hazard potential of dichromium nitride is in accordance with a Tier 2 assessment (using T/Dp data) performed with MECLAS version 4.5 (http://www.meclas.eu/accessed on 14.05.2018). The Metals Classification Tool (MECLAS) is a web enabled classification tool always updated to the latest classification guidance, legal ruling, information on toxicity references and available self-classifications.

In sum, it can safely be assumed that dichromium nitride does not meet classification criteria of an acute or long-term aquatic hazardof Regulation (EC) No 1272/2008.

 

 

Reference:

WHO (2009): Concise International Chemical Assessment Document 76 (CICAD). Inorganic chromium(III) compounds (evaluation), International Programme of Chemical Safety (IPCS), WHO, Geneva.