REACH Metals Gateway

Guidance on Complex Materials

Guidance on the classification of inorganic UVCB substances for Human Health hazards.

This industry note describes a tiered approach and its application to hazard classification of inorganic UVCB substances for human health hazards. The information necessary to conduct the assessment is identified at 3 levels: elemental composition, mineralogy / speciation, and information on bioaccessibility.

The tiered methodology described here has been implemented in the online tool MeClas which complies with the UN GHS and EU CLP classification procedures and is available free of charge at www.meclas.eu

The solution following the addition of the metal and/or its compounds. It will largely be determined by two processes: the extent to which it can be dissolved, i.e., its water solubility, and the extent to which it can react with the media to transform to water soluble forms. The rate and extent at which this latter process, known as ‘transformation’ for the purposes of this guidance, takes place can vary extensively between different compounds and the metal itself, and is an important factor in determining the appropriate hazard class.  

The OECD transformation and dissolution protocol (TDP, OECD 2001), is an effective approach to test the solubility (or lack) of metal and inorganic compounds in standard conditions. It allows to compare the soluble fraction 
(after a standard period of 7 and 28 days) with the subsequent acute and chronic Ecotoxicity Reference Values. 
For the classification of organics, degradation is considered when establishing the classification. The term ‘degradation’ refers to the decomposition of organic molecule and as such cannot be applied to metals. Rather, the substance may be transformed by normal environmental processes to either increase or decrease the bioavailability of the toxic species (‘transformation’).  
Environmental transformation processes of metals and metal compounds to non-bioavailable forms influences classification as hazardous to the aquatic environment, questions surrounding removal from the water column and whether such mechanisms should be taken into account for aquatic hazard classification has been open for many years. 

Industry has developed both the Unit World Model (UWM) and the Extended Transformation/Dissolution protocol (T/Dp-E) which respectively model and measure both removal and the absence of remobilisation due to resuspension, with the aim of making the concept (also known as ‘rapid removal’) applicable for the EU CLP.  

Last page update: 16 November 2023