Microplastic (MP) is an emerging contaminant that has generated intense public concern. A standardized approach for human risk assessment, both for inhaled and ingested MP, is not available to date. In addition to a lack of appropriate reference materials, there are analytical challenges in the detection and dose definition, and information about relevant physicochemical properties of MP materials that drive human toxicity is missing. Another challenge for scientists is the development of a tiered testing and assessment approach that is mainly based on mechanistic evidence from human in-vitro models. Fraunhofer ITEM scientists are addressing these topics in two projects: In the “Brigid” project recently launched by Plastics Europe, the oral route of exposure is under investigation, while the Cefic-LRI project aims to develop a tiered approach for the assessment of inhalable MP.
Based on solvent precipitation, the scientists initially developed appropriate methods for the generation of MP reference particles with an upper size fraction < 10 µm. At present, tools for visualization and quantification of MP particles in cells and biological matrices are under development. The aims of the next phase in the Cefic-LRI project are to identify MP descriptors that determine inhalation toxicity and to finally rank these descriptors by their relevance for the assessment of human health hazards from inhalation.