Oral exposure to micro- and nanoplastics: Developing a modular and flexible risk assessment framework for human health

Efficient strategies for the human health risk assessment of micro- and nanoplastics (MNPs) are urgently needed to address the complexity and diversity of these materials. Here, we propose a risk assessment framework for MNPs following the oral route of exposure. The framework is based on a flexible and modular approach, drawing on modern concepts in risk assessment, such as Integrated Approaches to Testing and Assessment (IATAs) or Adverse Outcome Pathways (AOPs), and substantially relies on New Approach Methodologies (NAMs). The framework is structured into three different main steps: i) basic physicochemical characterization of testing materials, ii) intestinal crossing, iii) hazard assessment testing. Each step of the framework is supported by scientifically sound methods, enabling a mechanistic and hypothesis-driven risk assessment of MNPs.