The classification of TiO2 by the European Chemical Agency in 2017 has initiated a series of events and discussions that forward a workshop on particle overload and the consequences drawn from rodent inhalation studies. After the EU classification of titanium dioxide, the suggestion has been raised that Poorly Soluble particles of Low Toxicity (PSLTs) can be evaluated as a group.  Collectively, these actions and proposals raise some important questions on how inhalation data is being applied to ensure the best science is used to evaluate, classify as to hazard and assess risk of inhaled particulate materials. To understand the science and events which surround the classifications of carbon black and titanium dioxide and potential future classification of PSLTs, Paul Borm (Nanoconsult) in collaboration with Kevin Driscoll sought perspective from 23 international experts extensively involved in inhalation toxicology research. This survey is the basis to organize a workshop on April 1st and 2nd 2019 in Edinburgh (UK), which will be hosted by the Institute of Occupational Medicine (IOM) and the University of Edinburgh (ELEGI), and sponsored by ICBA, TDMA and several other industrial sponsors. Participation is by invitation only and we anticipate to gather 40-50 participants from academia, regulatory gremia, and industry.

There is significant value to have discussions in an open forum with the opportunity for broader input and comment and determining where consensus exists on questions such as:

  • Is there a technical basis to evaluate PSLTs as a group? if so, how would they be defined?
  • Should distinctions be made in classifying materials depending on particle size, for example nano size materials versus larger micron size?
  • How should maximum tolerated doses be determined for inhalation studies with poorly soluble particles and how should responses above those levels be extrapolated?
  • Is the rat lung response to high doses of particles like titanium dioxide and carbon black unique to that species, or is the rat a human relevant, sensitive species”;