The approach to hazard classification of 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 8th Revised Edition of the GHS guidance (UN, 2019). 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, 2019).
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.
“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.”
(GHS, section 4.1.1)
Transformation AND Dissolution
“The level of the metal ion which may be present in solution following the addition of the metal and/or its compounds, will largely be determined by two processes: the extent to which it can be dissolved, and the extent to which it can react with the media to transform to water soluble forms.”
Degradability / Rapid Environmental Transformation and RemovaL
“For inorganic compounds and metals, the concept of degradability (GHS Chapter 4.1) has limited or no meaning. Rather, the substance may be transformed by normal environmental processes to either increase or decrease the bioavailability of the toxic species. (…) Speciation of the soluble form can be affected by pH, water hardness, and other variables, and may yield particular forms of the metal ion which are more or less toxic. In addition, metal ions could be made non-available from the water column by a number of processes (e.g. mineralization and partitioning). Sometimes these processes can be sufficiently rapid to be analogous to degradation in assessing chronic classification.”
(GHS, section A18.104.22.168 and A22.214.171.124)
Acute and chronic aquatic toxicity1
“Acute aquatic toxicity” means the intrinsic property of a substance to be injurious to an organism in a short-term aquatic exposure to that substance. Chronic aquatic toxicity means the intrinsic property of a substance to cause adverse effects to aquatic organisms during quatic exposures zhich are determined in relation to the life-cycle of the organism.” (GHS, section 4.1.1)
“In the water column, it is generally the dissolved metal ions which are of concern for toxicity.” (GHS, section A9.1.15)
“The hazard classification schemes for metals and metal compounds are limited to the hazards posed by metals and metal compounds when they are available (i.e. exist as dissolved metal ions).”
(GHS, section A126.96.36.199) (1) In practice, the toxicity of dissolved metal ions to aquatic organisms is evaluated based upon ecotoxicity data obtained for soluble inorganic metal compounds.
Physical forms, particle size and surface area
“Particle size, or moreover surface area, is a crucial parameter(…). Where it can be shown that the tested powder (…) has been produced by a special process and cannot be generated from the massive metal, classification of the massive can be based on testing of a more representative particle size or surface area, if such data are available. The powder may be classified separately based on the data generated on the powder.”
(GHS, section A188.8.131.52)
“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).”
(GHS, section 4.1.1)
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, 2019). 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, both forms of copper metal were considered rapidly removable from the water column. The concept that a metal may undergo rapid environmental transformation and removal (as equivalent to the degradability of organic substances) has not yet been accepted by all jurisdictions, nor has the conclusion that copper ions undergo rapid environmental transformation and removal.
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 a Chronic Aquatic Toxicity Category 2 hazard. Table 4.10 of the report summarizes these hazard classifications and presents the GHS hazard statement codes, when applicable. Tables 4.4 (copper massive) and 4.7 (copper powder) 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 2||H411: Toxic to aquatic life with long lasting effects|
Notes: CAS# = Chemical Abstracts Service Registration Number; EC# = European Community Number; GHS = Globally Harmonized System of Classification and Labelling of Chemicals (UN, 2019); M Factor = Multiplying Factor.
It is important to highlight some differences between the GHS and the European Union’s 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, 2019; 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 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.