"To group or not to group, this is the question” – but is that so relevant?

The first concerns about the potential hazardous effects induced by inhalation of occupational dust arose more than 100 years ago, when asbestos exposure was observed to be associated with lung diseases. Over the years, attention progressively shifted towards environmental air pollution (e.g., particulate matter, micro- and ultrafine particles, tire debris, combustion-derived particles). More recently, products of nanotechnology (e.g., nanoparticles, nanorods, nanowires) and advanced (nano)materials (e.g., composites, multicomponent nanomaterials, nanotubes) have come under scrutiny as potential sources of respirable toxicants. However, even after decades of research, particle and fibre inhalation toxicology still represents a major challenge for human and occupational risk assessment.
What have we learned from a century of research? How can we best exploit the existing knowledge? How can experimental efforts for chemical hazard and risk assessment be minimized while complying with the need to reduce animal testing?
Among the New Approach Methodologies for testing and assessment (NAMs), grouping and read across has emerged as a promising strategy for the hazard assessment of new materials. However, how can this approach cope with the increasing physical and chemical complexity of novel substances? Is the verification of the “grouping hypothesis” the only successful outcome of its application? A realistic case study will be analysed in an attempt to address these questions.

If you want to know more:
Stone et al 2020, Nano Today 35, https://doi.org/10.1016/j.nantod.2020.100941
Stone et al 2025, Materials Today 90, https://doi.org/10.1016/j.mattod.2025.08.024