Application of the Tier 3 NIOSH occupational exposure banding process for the graphene family of nanomaterials: A case study

Graphene is a class of two-dimensional (2D) nanomaterials composed of single or multiple layers of carbon atoms. To date, there are limited clinical data and no epidemiological research available to assess graphene toxicity in humans. Despite the growing amount of animal toxicity data, there are currently no occupational exposure limits (OELs) for any type of graphene nanomaterial published by international authoritative organizations to ensure their safe handling within workplaces. In the absence of consensus OELs for graphene, the National Institute for Occupational Safety and Health (NIOSH) occupational exposure banding process was used to assign an occupational exposure band (OEB). The NIOSH banding process is organized into a three-tiered system and is a resource for occupational safety and health (OSH) professionals to guide risk management and exposure control decisions when OELs are not available. To the authors' knowledge, there are no Globally Harmonized System of Classification and Labeling of Chemicals (GHS) H-codes/statements available for graphene to conduct a Tier 1 analysis. Even though data were available from authoritative sources for three of nine health endpoints, the data were insufficient to support banding in a Tier 2 assessment. Therefore, a Tier 3 assessment using the NIOSH banding process was applied to the graphene family of nanomaterials (GFN) as a case study based on the specific physicochemical and toxicological properties with uncertainty factor adjustments. The band assignment was replicated by three individuals with advanced toxicology and industrial hygiene knowledge to ensure a consistent outcome. The results found that three of the six endpoints banded were "E," representing an air concentration ≤0.01 mg/m³, while the other three ranged from "A" to "C." This indicates that the graphene materials evaluated may have potential effects at low exposure concentrations (≤0.01 mg/m³). These findings suggest an OEB may be a suitable option for OSH professionals attempting to mitigate risk for GFN in the absence of an OEL and may provide a reasonable initial estimate for recommended workplace exposure and control measures.