• Project number: F 2528
• Institution: Federal Institute for Occupational Safety and Health (BAuA)
• Status: Completed Project

Description:

When new materials are developed, this not only creates opportunities for innovative products and more efficient production processes, but also requires the systematic identification and consideration of potential safety and health risks during man-ufacturing and use.

The HARMLESS project pursued a new approach to support the safe design of in-novative materials. Modern testing methods (NAM) were integrated into a user-friendly toolbox and combined with a digital decision-support system that automatically selects suitable methods and presents results in a comprehensible way. The aim was to provide companies of all sizes — including small enterprises — with straightforward access to reliable safety information. Case studies helped to test and further refine the system under real-world conditions.

BAuA investigated the ability of phagocytic cells to remove fibrous particles from the lung and which fibre properties can inhibit this process. In addition to the already known influence of length, respirability, and biopersistence, the results showed that high bending stiffness of fibres is also a decisive factor preventing their uptake by phagocytic cells. Together, these four properties sufficiently characterize fibres to allow the derivation of potential health risks and their classification as “critical fibres.” They also form the basis for developing guidelines for innovative fibre material design that ensure a high level of chemical safety and support sustainable development.

Based on laboratory findings and model calculations, a threshold value for bending stiffness (rigidity) was determined, below which fibres can be bent and compacted by cells and thus fully internalized. This threshold was also used to derive a minimum fibre diameter, which has been included as an important criterion for critical fibres in regulatory proposals.

Another research focus examined the tendency of multi-walled carbon nanotubes (MWCNTs) to release critical fibres into the air under mechanical stress, where they could potentially be inhaled. The results showed that the release of individual fibres strongly depends on their arrangement within the powder and on their stiffness. These characteristics, in turn, depend on the manufacturing process. By combining microscopic diameter measurements with model-based estimates, a method was developed to classify MWCNT powders into low, moderate, or high propensity to re-lease critical fibres. This enables prediction of situations in which processing is likely to result in increased release of individual critical fibres.

With the new approach developed in this project, the practical toolbox and digital decision-support system, the safe development of new materials is now facilitated and risk assessment made more transparent and accessible.