Particles Platform Workshop Outcomes – 2 October – 2025 “A Proportionate approach to the regulation of particles based on the latest science”
The Particles Platform Workshop, titled "A Proportionate approach to the regulation of particles based on the latest science" was held on 2 October 2025 in Brussels and online.
The Workshop covered the latest scientific and regulatory developments concerning particles, with a particular focus on defining and categorising “poorly soluble low toxicity particles” (PSLTs)
and their broader health and regulatory implications. Key topics included the need for a clear and holistic definition of PSLTs, the importance of understanding particle characteristics and their interactions with biological systems, and the importance for industry of harmonising regulatory approaches at both the European and international levels, particularly related to classification as Specific Target Organ Toxicity – Repeated Exposure (STOT RE). The discussion also explored the impact of recent legal decisions, such as the annulment of the harmonised classification and labelling (CLH) under the Classification and Labelling Regulation (CLP) of certain forms of titanium dioxide (TiO₂), and the complexity of the legal and scientific frameworks applicable to particles.
The way forward will require continuous scientific dialogue to refine the definitions and scope of key terms like PSLTs, and to ensure future regulations remain proportionate, transparent, and based on the latest science. The workshop highlighted the value of international harmonisation and further collaboration among regulators, scientists, and industry to close possible regulatory gaps and safeguard both workers and public health.
Read the full workshop summary here.
As a follow up, the Particles Platform Partners recommend the establishment of an ECHA Expert Group with experts from ECHA, the Commission, member states, academia, industry
and other stakeholders to address the scientific and regulatory challenges related to particles including the following aspects:• Targeted update of OECD guidance document 39 for inhalation of particles and the guidance values for STOT RE in the UN GHS
• How to apply the outcome of inhalation studies on rats for human health assessment
• The use of new approach methodologies (NAMs) including in vitro and in silico models for hazard assessment of particles
• Updating the ECHA Guidance on CLP for particle-related aspects such as lung overload in rat inhalation studies
• Follow the developments of the ECHA PSLT scoping project for occupational exposure limit values (OEL) and provide feedback to ensure an integrated approach
