The approach to hazard classification of relatively insoluble metals such as copper is different from that for organic compounds, with a number of specific guiding principles and study designs. This approach is presented in Annex 9 of the 7th Revised Edition of the GHS guidance (UN, 2017). The environmental hazard assessment described in the report follows the principles and criteria presented within Annex 9, specifically Section 7.5 (“Application of classification criteria to metals and metal compounds”; UN, 2017).
Determining GHS environmental hazard classifications for various forms of copper metal is done by comparing the available aquatic toxicity data for copper ions and solubility data for specific forms of copper. In other words, GHS hazard classifications are determined by comparing the intrinsic toxicity of the copper ions to the rate and amount of ions that enter solution for each form of copper metal. Key concepts that support this approach are defined below.
“Bioaccumulation means net result of uptake, transformation and elimination of a substance in an organism due to all routes of exposure (i.e. air, water, sediment/soil and food).”
“Bioavailability (or biological availability) means the extent to which a substance is taken up by an organism, and distributed to an area within the organism. It is dependent upon physico-chemical properties of the substance, anatomy and physiology of the organism, pharmacokinetics, and route of exposure. Availability is not a prerequisite for bioavailability.”
“Bioconcentration means net result of uptake, transformation and elimination of a substance in an organism due to waterborne exposure.”
Removal/Partitioning from the Water Column
“Metals and metal compounds can undergo interactions with the media which affect the solubility of the metal ion, partitioning from the water column, and the species of metal ion that exists in the water column. In the water column, it is generally the dissolved metal ions which are of concern for toxicity. The interaction of the substance with the media may either increase or decrease the level of ions and hence toxicity. It is thus necessary to consider whether metal ions are likely to be formed from the substance and dissolve in the water, and if so whether they are formed rapidly enough to cause concern.”
The aquatic environment hazard classification of all copper forms considered bioavailability through the use of transformation-dissolution data, as described in GHS Annex 9 (UN, 2017). Copper does not bioaccumulate because it is an essential element: tissue concentrations in organisms are well-regulated, and the bioconcentration factor decreases with increasing copper exposure. In addition, all three forms of copper metal were considered rapidly removable from the water column. The concept of a metal being “rapidly removable” from the water column has not yet been accepted by all jurisdictions, nor has the conclusion that copper metal should be considered rapidly removable from the water column for the purpose of GHS hazard classification. Various international bodies are conducting ongoing discussions that aim to reach an agreed-upon approach to assessing the persistence and degradability of metals, based on the best available science, for the purposes of classifying their environmental hazards.
Copper massive is classified as an Acute Aquatic Toxicity Category 3 hazard. Copper powder is classified as an Acute Aquatic Toxicity Category 1 (M factor = 1) and Chronic Aquatic Toxicity Category 3 hazard. Finally, coated copper flakes are classified as an Acute Aquatic Toxicity Category 1 (M factor = 10) and Chronic Aquatic Toxicity Category 2 hazard. Table 4.13 of the report summarizes these hazard classifications and presents the GHS hazard statement codes, when applicable. Tables 4.4 (copper massive), 4. 7 (copper powder), and 4.10 (coated copper flakes) of the report also present summaries of the justifications for each classification.
Table 4.13 Summary of GHS Environmental Hazard Classifications for Copper Metal Forms
|Copper Metal Form||GHS Hazard Classifications||GHS Hazard Statement Code|
CAS: 7440-50-8, EC: 231-159-6
|Acute Aquatic Toxicity Category 3||H402: Harmful to aquatic life|
CAS: 7440-50-8, EC: 231-159-6
|Acute Aquatic Toxicity Category 1 (M factor = 1)||H400: Very toxic to aquatic life|
|Chronic Aquatic Toxicity Category 3||H412: Harmful to aquatic life with long lasting effects|
|Coated Copper Flakes|
No CAS or EC numbers allocated
|Acute Aquatic Toxicity Category 1 (M factor = 10)||H400: Very toxic to aquatic life|
|Chronic Aquatic Toxicity Category 2||H411: Toxic to aquatic life with long lasting effects
Notes: GHS = Globally Harmonized System of Classification and Labelling of Chemicals (UN, 2017); M Factor = Multiplying Factor.
It is important to highlight some differences between the GHS and the European Union’s Harmonized Classification, Labelling, and Packaging classifications (CLP) classification schemes. One important difference is that the GHS includes Acute Aquatic Toxicity Categories 1, 2, and 3, while the CLP scheme only includes Category 1 for acute aquatic toxicity hazard (UN, 2017; ECHA, 2017). Similarly, the South Korean guidance on classifying acute aquatic toxicity hazards includes only Acute Aquatic Toxicity Category 1. As a result, substances cannot be classified as Acute Aquatic Toxicity Category 2 or 3 hazards in those jurisdictions. In addition, other jurisdictions (e.g., the United States and Canada) have not adopted hazard categories for any aquatic toxicity hazards. These differences between the various hazard classification schemes and how they are adopted (or not) by different jurisdictions may thus result in differing aquatic toxicity classifications for the same metal, even when the same data are evaluated.
It is also worth noting that, although the GHS hazard classification for chronic aquatic toxicity for coated copper flakes (i.e., Category 2) is based on the most relevant currently available data, coated copper flakes are assigned a mandatory Category 1 hazard (M factor = 1) under the CLP (EC No. 1272/2008; EC, 2016). The CLP classification for chronic aquatic toxicity used a surrogate approach, because the chronic toxicity data for coated copper flakes were considered inadequate at the time (ECHA, 2014a). In addition, the assessment of coated copper flakes did not consider copper to be rapidly removable from the water column (ECHA, 2014a).