Development of a nano-specific safe-by-design module to identify risk management strategies

This article describes the development of a Safe-by-Design (SbD) module and its integration into an easy-to-use tool, named the Nano Exposure Quantifier-Safe-by-Design (NEQ-SbD) tool. The NEQ-SbD tool guides its user to lower the exposure to nanomaterials at the worksite where nanomaterials are manipulated or handled during a wide range of activities. This allows the tool user with an informed decision to assess airborne exposure and to select, compare, and identify appropriate risk management measures (RMM). The SbD module was developed using various information sources that can support and guide the SbD process, including the (i) RMM effectiveness based on analyses of an Exposure Control Efficacy Library (ECEL), (ii) RMM performance using a Computational Fluid Dynamics (CFD) model, (iii) e-cards based on a qualitative analysis of RMM information sources, and (iv) guidance for SbD strategy using an exposure directionality assessment. This information has been integrated in the user interface of the SbD module and NEQ-SbD tool to facilitate the SbD decision-making process. The SbD concept applied in the integrated NEQ-SbD tool introduces a comparison between a baseline exposure assessment and an (improved) SbD exposure assessment. The integrated NEQ-SbD tool consists of 4 modules including (i) a baseline exposure assessment, (ii) baseline results, (iii) SbD assessment, and (iv) SbD comparative results. The main purpose of the SbD module lies in guiding the user to the most sensitive (exposure) parameters and allowing a side-by-side comparison of potentially suitable RMMs. The integrated NEQ-SbD tool also offers a tiered approach and seamlessly shifts from a tier-1 to tier-2 uncertainty of an exposure assessment. The SbD module is illustrated using a worked example for the transfer of nano powders, showing the possibility of identifying SbD solutions for both safe-by-process and safe-by-material design purposes. The NEQ-SbD tool is a valuable tool for the SbD of nanomaterials and as a decision-making tool to support SbD risk management strategies that lead to minimizing health risks associated with occupational exposures.