Background
There are a number of trace elements that were considered just as laboratory curiosities but now, however, are key components for the development of new technologies. For most of these elements, the present understanding of their concentrations, transformation and transport in the different environmental compartments is scarce and/or contradictory. These elements, here defined as technology-critical elements (TCEs) – and include Ga, Ge, In, Nb, Ta, Te, Tl, the platinum group elements (PGE: Ir, Os, Pd, Pt, Rh and Ru), and most of the rare earth elements (REE: Ce, Dy, Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Sm, Tb, Y, Yb) – are undergoing a significant change in their cycle at the Earth’s surface due to their increase use in a variety of technological applications. Their impact on their biogeochemical cycles and potential biological and human health threats needs to be further explored.
The current significant gaps in the knowledge on TCEs, from their environmental levels and fate to their potential (eco)toxicological impact, are mainly explained by two factors: (i) their typical ultra- trace concentrations, making their analytical determination extremely difficult and/or time- consuming, and (ii) the absence of any significant industrial role (apart some biomedical applications) prior to their massive use in the increasing demand of new technological applications, therefore discouraging scientists to assess the (eco)toxicological aspects of the TCEs. However, this scenario is changing rapidly and substantially. The current use of TCEs in new technological products is resulting in significant changes in the processes associated with their natural environmental cycle at the Earth’s surface due to increased mining activities, use in a variety of products, increased exposure of the biosphere, unknown biogeochemical or anthropogenic cycling and unknown potential toxicological endpoints and harmful effects. At all stages of their life cycle, these elements and their compounds can be released into the environment and come in contact with the biosphere. The wider impact of the increasing use of many TCEs within a range of environmental compartments is poorly understood; for several TCEs no field data is available.
Technology-critical elements (TCEs) in red
The need for an evaluation and assessment on the analytical, environmental and toxicological aspects of the TCEs
The current significant gaps in the knowledge on TCEs, from their environmental levels and fate to their potential (eco)toxicological impact, are mainly explained by two factors: (i) their typical ultra-trace concentrations, making their analytical determination extremely difficult and/or time-consuming, and (ii) the absence of any significant industrial role (apart some biomedical applications) prior to their massive use in the increasing demand of new technological applications, therefore discouraging scientists to assess the (eco)toxicological aspects of the TCEs.
However, this scenario is changing rapidly and substantially. The current use of TCEs in new technological products is resulting in significant changes in the processes associated with their natural environmental cycle at the Earth’s surface due to increased mining activities, use in a variety of products, increased exposure of the biosphere, unknown biogeochemical or anthropogenic cycling and unknown potential toxicological endpoints and harmful effects. At all stages of their life cycle, these elements and their compounds can be released into the environment and come in contact with the biosphere. The wider impact of the increasing use of many TCEs within a range of environmental compartments is poorly understood; for several TCEs no field data is available.
