Industrywide exposure assessment study of workers exposed to graphene and other two-dimensional nanomaterials

National Institute Of Environmental Health Sciences

Investigators

Abstract

The past decade has witnessed an extraordinary increase in research progress and innovation on ultrathin two-dimensional (2-D) nanomaterials. These 2-D nanomaterials include industrial scale materials, such as graphene, as well as emerging materials such as hexagonal boron nitride, silicene, molybdenum disulfide, and many others that have generated considerable interest as they demonstrate a vast array of unique physical properties. Two-dimensional nanomaterials offer great potential in numerous applications such as in electronics, energy storage, water remediation, paints and coatings, sensors, lighting, composites, and biomedicine. As the utilization of 2-D nanomaterials continues to rise, with greater expansion into industrial applications, the potential for workplace and environmental exposures throughout the life cycle of these materials will successively increase as well. To date, there have been relatively few studies in the published literature evaluating the toxicity of these materials, and even fewer data are available regarding workplace exposures and the development of exposure assessment methodologies. In FY23, the study team conducted five site visits to companies handling or producing graphene materials and recruited 20 additional individuals that participated in the industrial hygiene sampling. The companies visited included a facility that functionalized graphene oxide materials and four graphene manufacturers that produced a variety of different types of materials which included graphene nanoplatelets and graphene oxide materials of few-layers and multi-layers. Several of these facilities had the capacity to produce up to a half a ton of graphene materials daily. The study team is currently developing a manuscript that will assign an exposure band for graphene based on the available in vivo and in vitro animal toxicity data. Since there are no occupational exposure limits for graphene, using this approach will create a benchmark that will provide a meaningful context for the collected exposure measurements, giving the participating companies, and the graphene industry as a whole, the ability to make safety and health decisions based upon their air sampling results. Finally, laboratory experiments characterizing the physical properties and assessing the dispersibility in air (dustiness) were also completed for five industrially relevant graphene materials and may be compared to seven industrially relevant graphite materials and one carbon black. The relative dustiness or exposure potential between the bulk powders will be compared, and the resulting aerosol size fractions will be used to help interpret exposure concentrations measured during site visits. The results of the dustiness experiments are currently being drafted into a manuscript for submission to a scientific journal in early FY24.