Occupational exposure to graphene and silica nanoparticles. Part I: workplace measurements and samplings

Few-Layers Graphene (FLG) are able to improve the performance of materials, due to their chemical-physical properties. Engineered amorphous silica nanoparticles (SiO₂NPs) are among the most widespread nanomaterials (NMs) in the world. Such nanomaterials are two case studies of the research project 'NanoKey' that integrated the exposure assessment through personal measurements and sampling in the workplace, as described in the present work (part I), with the biomonitoring of exposed workers (reported in part II). Measurement campaigns were conducted according to OECD and WHO harmonized approach in two production sites. The set of instruments included real-time devices for high-resolution measurements at the nanoscale and time-integrated samplers for the off-line gravimetric analysis and chemical and morphological (SEM-EDS) characterization of exposure in order to identify the contribution of production compared to the background. Values of particle number concentration (PNC) and lung deposited surface area (LDSA) within the FLG production resulted higher than the background far field (FF), even if they are always similar to the near field (NF) ones: the average diameter (D_avg) during the production was higher than the NF background but always lower than the FF values. SEM-EDS analysis highlighted the presence of structures comparable to those produced. During the SiO₂NPs production, the PBZ values showed PNC and LDSA levels higher than the background, with a decrease in the D_avg probably due to NPs emission. SEM-EDS confirms the presence of rare silica nanoparticles. Since the exposure to airborne NMs cannot be excluded in both production sites, a prevention-through-design approach to mitigate the potential risk for workers has been recommended.