Barium oxide (BaO), solid soln. with calcium oxide, magnesium oxide, phosphorus oxide (P2O5), strontium oxide and zinc oxide, copper-doped

Ecotoxicological Summary

Conclusion on classification

The standard approach for classifying poorly soluble metals is to use the data generated from T/D tests, and compare this with relevant acute or chronic Ecotoxicity Reference Values (ERV) for the soluble metal compounds (Guidance on the application of the CLP criteria, ECHA, 2017).

The T/D tests for strontium apatite, copper doped have revealed that both copper and strontium are released from the UVCB in test medium at pH 6 to a larger degree than at pH 8, therefore the results at pH 6 are taken into consideration for classification purposes as a worst-case scenario.

According to the guidance on CLP criteria (ECHA, 2017) the acute and chronic hazard should be assessed for a metal compound if the respective acute or chronic ERV value for the metal ion of concern is ≤1 mg/L. A metal should be classified for acute aquatic hazard if the dissolved metal ion concentration after a period of 7 days at a loading rate of 1 mg/L exceeds the acute ERV. Where the chronic ERV for the metal ions of concern is ≤ 1 mg/L, the 28-day results from the T/D test should be used to aid classification.

For strontium, the lowest acute toxicity value is an unbounded 96-h LC50 of >40.3 mg Sr/L for fish, Cyprinus carpio[1]. The lowest chronic NOEC of 21 mg Sr/L was reported for Daphnia magna (Biesinger and Christensen 1972).The acute and chronic ERV values for strontium are >1 mg/L therefore strontium does not need to be taken into account in the classification for environmental hazard.

For copper, a significant number of short- and long-term aquatic data is available. The lowest acute toxicity value reported for copper at pH 6 is a LC50 of 4.4 µg Cu/L (Errickson et al. 1996[2]).The second lowest acute value at pH 6 is a LC50 of 9.5 µg Cu/L reported for Ceriodaphnia dubia (Schubauer-Beringan et al. 1993). The LC50 of 4.4 µg Cu/L was determined in a study with larvae of fathead minnows (< 24 h old) and is an outlier to the other acute effect values for copper and therefore is considered as an unreasonable worst-case. For that reason, the value of 9.5 µg Cu/L from the study with C. dubia (Schubauer-Beringan et al. 1993) is used as the acute ERV for classification of strontium apatite, copper doped. A large amount of chronic data are available for copper. The lowest chronic NOEC value of 4.2 µg Cu/L at pH 6.3 was determined in a toxicity study with Pseudokirchneriella subcapitata conducted according to the OECD 201 guideline (Heijerick et al. 2005) and this value is used as the chronic ERV for classification of strontium apatite, copper doped. Although there is a large number of studies with copper, the values selected from the studies abovementioned are considered to represent a sufficient level of protection for the environment and therefore are used as acute and chronic ERVs for classification of strontium apatite, copper doped.

Based on comparison of copper solubility determined in the T/D study with relevant ERV values, strontium apatite, copper doped is assigned an acute classification Aquatic Acute 1, as the concentration of dissolved copper released after 7 days in the TD test is higher than the acute ERV for copper. There is no data on the release of copper at loading rate of 0.1 mg/L after 28 days. However, based on the composition of strontium apatite copper doped the maximum possible release of copper at 0.1 mg/L loading rate is 2.78 µg/L. Therefore, the substance does not need to be classified as Aquatic Chronic 1. The dissolved copper concentration released after 28 days in the T/D test at a loading rate of 1 mg/L is greater than the chronic ERV value derived for soluble copper, therefore strontium apatite, copper doped is classified as Aquatic Chronic 2. The comparison of copper solubility determined in the T/D study with relevant ERV values and the impact on classification are presented in the following table:

Table 1              Determination of classification of strontium apatite, copper doped

Constituent	Acute hazard			Chronic
	Copper release (µg/L)* 7 days	ERV (µg/L)	Proposed classification	Copper release (µg/L)* 28 days	ERV (µg/L)	Proposed classification
Copper	17.68	9.5	Acute 1**	20.91	4.2	Chronic 2

* In the T/D test at 1 mg/L loading rate

**An M factor should be derived for any substance classified as Acute or Chronic Category 1 for the environment. M factors allow the appropriate classification of mixtures containing these substances to be derived, and allow the more environmentally hazardous components to be more highly weighted than less hazardous components.

Although strontium apatite, copper doped is classified as Acute Category 1 it is not appropriate to derive M factors for this complex UVCB. If this substance was present in a mixture then it would be more appropriate (and simpler) to derive the classification based on the component substances directly, rather than by using the classification of the strontium apatite, copper doped.

 

 

 

[1]Based on ECHA dissemination portal, accessed on 27^thDecember 2017.

[2]Erickson RJ, Benoit DA, Mattson VR, Nelson HP Jr., Leonard EN. 1996. The effects of water chemistry on the toxicity of copper to fathead minnows. Environ Toxicol Chem 15: 181-193