Slimes and Sludges, copper electrolytic

Endpoint summary

Additional information

The hazard assessment of inorganic UVCBs for the purpose of classification and derivation of fate properties and safe effect thresholds (e.g. PNEC) is a cumbersome and complex process. Due to the intrinsic variability of the composition of an UVCB, it is difficult to select a sample that would unambiguously be representative for the (eco)toxicological hazard profile of the UVCB and could subsequently be used for testing. Instead of direct testing, a precautionary approach is taken where the UVCB is treated as a complex metal containing substance containing a number of discrete constituents (metals, metal compounds, non-metal inorganic compounds etc.). For each of these constituents, the fate and hazard profile is used for deriving the proper classification of the UVCB (using the mixture rules) and/or for the derivation of the PNECs of the constituent (forwarded to the risk assessment). Using the fate of all individual constituents circumvents indirectly the issue of varying composition of an UVCB as it implicitly assumes that each time the UVCB substance consists of the pure substance, i.e. that each constituent would be present and bioavailable at a 100% concentration in the UVCB substance. This can be considered a conservative approach. A main outcome of the constituents’ based assessment is the selection of all the constituents for which any environmental hazard is identified. This selection defines the scope of the further exposure and risk assessment (CSR, Ch. 9&10).

 

The actual hazard profile and environmental fate properties of the inorganic UVCB substance and the individual constituents are dependent on the speciation of each and every constituent andhence this information needs to be collected and the correspondinginformation for the environmental fate properties will be used. Different scenarios can be encountered.

·      When the speciation of a constituent is known, this is used as such for the environmental fate properties assessment.

·      When the speciation is unknown or few metal species co-exist, the worst-case speciation for the purpose of environmental fate assessment and environmental hazard assessment is selected, i.e. the speciation that would lead to the most severe effects.

The UVCB is a complex inorganic metals containing substance. The physico-chemical characterization of the UVCB (see relevant section in IUCLID) demonstrates the presense of different metal speciation; intermetallic, metal sulphates and metal oxides that settled down and precipitated during electro refining. This resulted in relatively high solubilisation potential in water for most of the metals present in the UVCB (e. g. Cu, Ag, As).

More particularly the following needs to be taken into account when considering information on environmental fate of this UCVB:

Stability and bio degradation: The classic standard testing protocols on hydrolysis, photo-transformation and biodegradation are not applicable to inorganic substances such as this UVCB. This was recognized in the Guidance to Regulation (EC) No 1272/2008 Classification, Labelling and Packaging of substances and mixtures (metal annex): “Environmental transformation of one species of a metal to another species of the same does not constitute degradation as applied to organic compounds and may increase or decrease the availability and bioavailability of the toxic species. However as a result of naturally occurring geochemical processes metal ions can partition from the water column. Data on water column residence time, the processes involved at the water – sediment interface (i. e. deposition and re-mobilisation) are fairly extensive, but have not been integrated into a meaningful database. Nevertheless, using the principles and assumptions discussed above in Section IV.1, it may be possible to incorporate this approach into classification.”

As outlined in CLP guidance (2009), understanding of the rate and extent of transformation/dissolution of sparingly soluble inorganic substances to soluble, potentially available metal species is relevant to the environmental hazard assessment.

Given the dominant presence of metal sulphates in this complex UVCB and the high solubilization potential observed for several metals (see physico-chemical characterisation Liipo, 2010), no transformation/dissolution data was carried out and a conservative approach was adopted by considering the UVCB as fully soluble in water.

Attenuation of the released metal ions: once released from the UVCB, the metal-ions will be sorbed to mineral and particulate organic matter surfaces in the water, sediment and soil and will bind to the dissolved organic and sulphide materials present in water, soil and sediment compartments. Binding, precipitation and partitioning allows for a reduction of "bio-available metal species" and thus potential metal toxicity as a function of time.

Transport and distribution: assessing transport and distribution of the UVCB substance has no meaning. The mechanisms of distribution over liquid/solid phase (adsoprtion/desorption, precipitation and removal from water column) of the metals contained in the UVCB have been assessed in the respective risk assessments and/or Chemical Safety reports. Partition coefficients for soil/water, sediment/water and suspended matter/water are available for different metals contained in the UVCB and further used for environmental exposure assessment, if relevant.

Bioaccumulation and secondary poisoning: the assessment of the bio accumulation and secondary poisoning potential of this UVCB as no meaning. Accumulation data (BCF and BAF values) are available for relevant metal constituents of this UVCB. Metals like Cu, Zn for example are essential and well regulated in all living organisms and therefore the bioaccumulation criterion is not applicable. While some metals do not magnify in aquatic and terrestrial systems, for other metals secondary poisoning is to be considered relevant based on their known bioaccumulation potential.

According to the CLP Guidance for complex substances (section III 3.2) it is not recommended to estimate an average or weighted BCF value but identify one or more constituents for further consideration. Therefore, secondary poisoning of some constituents contained in the UVCB was further taken into account in the environmental exposure assessment.

 

Summary of the information on environmental fate and pathways for the purpose of classification:

The UVCB environmental hazard assessment is driven by the hazard assessment of the individual UVCB constituents. For the purpose of the hazard assessment, the UVCB is treated as a complex metal containing substance with a number of discrete constituting compounds (metals, metal compounds, non-metal inorganic compounds). The hazard classifications of each compound are then factored into a combined classification of the UVCB as a whole. For environmental endpoints, additivity and/or summation algorithms are applied to quantitatively estimate the mixture’s toxicity to aquatic organisms. More information can be found in the MECLAS output (see Annes I of the CSR). No further specific environmental fate information on the constituents is required to directly derive the hazard of the UVCB. Since the removal from the water column behaviour of the individual constituents can have an indirect impact on their respective environmental classification, an overview is given in the table below.

 

Table18:Summary of the information on environmental fate and pathways for the purpose ofclassification

UVCB constituent			Attenuation/ removal from water column
Element	Speciation used for classification
Cu	Cu sulfate	yes, see Waeterschoot et al (2012) and MECLAS (Annex I of this CSR)
Ag	Ag powder	No, see Waeterschoot et al (2012) and MECLAS (Annex I of this CSR)
Ni	Ni sulfate	Yes, see Waeterschoot et al (2012) and MECLAS (Annex I of this CSR)
Pb	Pb compounds	Yes see Waeterschoot et al (2012) and MECLAS (Annex I of this CSR)
Co	Co sulfate	No see Waeterschoot et al (2012) and MECLAS (Annex I of this CSR)
Zn	Zn sulfate	Yes see Waeterschoot et al (2012) and MECLAS (Annex I of this CSR)
Sn	Sn compounds	Yes see Waeterschoot et al (2012) and MECLAS (Annex I of this CSR)
Sb	Sb2O3	Yes see Waeterschoot et al (2012) and MECLAS (Annex I of this CSR)
Te	TeO2	No see Waeterschoot et al (2012) and MECLAS (Annex I of this CSR)
Se	Se metal	No see Waeterschoot et al (2012) and MECLAS (Annex I of this CSR)
Ba	Ba sulfate	No see Waeterschoot et al (2012) and MECLAS (Annex I of this CSR)
As	4.13% As, 10.18% Arsenic compounds and 85.69% As2O3	No see Waeterschoot et al (2012) and MECLAS (Annex I of this CSR)
Bi	Bi compounds	No See Waeterschoot et al (2012) and MECLAS (Annex I of this CSR)
S	SO4^2-sulfate	Taken into consideration in corresponding metal sulfates

* see IUCLID/CSR section 1.2 composition and IUCLID 4.23 additional Physico-chemical Information

Summary of the information on environmental fate and pathways for the purpose of risk assessment:

The environmental (risk) assessment is based on all constituents of the UVCB that are hazardous to the environment. For the environment, most often, it is the metal ion that is the toxic driver (ECHA, 2008, R.7.13-2). Considering the composition and physico-chemical characterisation of this UVCB, full solubilisation of the various constituting species is assumed in the aquatic environment.

 

Table19:Summary of the information on aquatic environmental fate and pathways for thepurpose of risk assessment

UVCB constituent			Transport/ distribution		Bio accumulation		Secondary poisoning
Element	Speciation used for environmental fate
Cu	Metal ion	Partitioning coeff. available	No See McGeer et al., 2013	Not needed
Ni	Metal ion	Partitioning coeff. Available	BCF value available	Quantitative assessment conducted
Pb	Metal ion	Partitioning coeff. Available	BCF value available	Quantitative assessment conducted
As	Metal ion	Partitioning coeff. Available	BCF value available	Quantitative assessment conducted
Zn	Metal ion	Partitioning coeff. Available	No See McGeer et al., 2013	Not needed
Ba, Co, Sn, Sb, Te, Se, Ag	Metal ion	Quantitative exposure assessment conducted*	Quantitative exposure assessment conducted*	Quantitative exposure assessment conducted*
S	Sulphate ion	Qualitative exposure assessment conducted*	Qualitative exposure assessment conducted*	Qualitative exposure assessment conducted*

* More information on the scope of the UVCB assessment can be found in section 9 of the CSR.

When quantitative exposure and risk assessment were conducted on a metal constituent, the environmental fate information on this individual metal is reported in the respective IUCLID endpoint summary sheet. The information is taken from the respective metal REACH IUCLID dossiers (see Annex II of this CSR) and is summarized in the table below.

 

Table20:Overview of solid water partition coefficients (Kd), bioaccumulation factors and the fraction of emission directed to water by STP for the Copper intermediates.

	Unit	Cu	Pb	As	Ni	Zn
Suspended matter (freshwater)	L/Kg	30,246	295,121	10,000	26,303	110,000
Suspended matter (marine)	L/Kg	131,826	1,518,099	10,000	15,848	6,010
Sediment (freshwater)	L/Kg	24,409	154,882	6,607	7,079	73,000
Soil	L/Kg	2,120	6,400	191	724	158
BCF/BAF (aquatic)	L/kg	NR	1,553	270 (fresh) 5,866 (marine)	270	NR
BCF/BAF (terrestrial)	kg/kg dw	NR	0.39	NA		NR
Removal rate STP to sludge	%	80	84	26*	40	82
Reference		Cu CSR (2010)	Pb CSR (2010)	Crommentuyn et al. (1997)	Ni CSR (2010)	Zn CSR

*The fraction of Arsenic removed by a biological STP was calculated by means of EUSES 2.1.