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Environmental fate & pathways

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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 and DNELs 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 bio-available 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 and hence this information needs to be collected and the corresponding information 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.

Conclusions on environmental fate properties are based on available and/or environmental fate worst-case speciation information for each of the iUVBC constituents. Environmental fate properties for the iUVCB are assessed by assessing constituents’ transport and distribution, bioaccumulation potential and secondary poisoning. The other parameters, such as biodegradation or hydrolysis, are not applicable or relevant for inorganic constituents.

 

The iUVCB classification is calculated by applying the CLP mixture rules based on the classification of the known or worst-case speciation for each constituent and worst-case constituent concentration in the iUVCB (i.e. maximum of the legal entity typical value), using the MeClas tool. Depending on the availability of information, the iUVCB classification can be refined following the MeClas Tiered approach.

The quantitative assessment of "Slimes and sludges, electrolytic refining of tin, lead and silver containing alloy" is based on the Sn, Ag, Sb, Pb, As and Ni constituents, because other constituents, except for HBF4, do not significantly add to the hazard properties of this UVCB (see classification and labelling). Because HBF4 only results in hazards for eyes, this is covered in a qualitative way.