CEM - Abstract

Abstract Information :

Incidental nanoparticles (INPs) are unintentionally generated because of an anthropogenic process, such as high energy industrial processes: engines combustion, plasma cutting, welding, laser ablation, iron casting, thermal spraying, firing, etc. These industrial processes can be defined as permanent releasers to workplace air of INPs (up to millions of NP/cm3), which may lead to chronic exposures if these sources are not recognized as such and if control measures are omitted or not adequately designed. Therefore, at present, concentrations are frequently in exceedance of the non-binding recommendations, referred to as nanoreference value (NRV: 4·104 NP/cm3). The NRV proposed for INPs is the limit established for manufactured nanomaterials group 2b, due to there are no specific limit values for INPs. The definition of limit values, as a tool for preventive risk assessment, requires the availability of information on the characterization of the nanoparticle properties in the processes responsible for the generation of INPs for ranking their hazards in the existing or adapted provisional NRVs. The aim of this work was to assess occupational exposure to INPs in work environments occurring during critical industrial activities such as ceramic tile firing and thermal spraying of ceramic coatings. For the latter activity, the case studies selected were high-velocity oxy-fuel thermal spraying (HVOF) and atmospheric plasma spraying (APS). The detailed INPs characterisation, will allow us to evaluate the appropriateness of the current NRV and optimise the performance of tailored risk management tools to minimize the impact of INPs. In this regard, an exhaustive characterisation of INPs has been carried out in three representative industrial scenarios: Nanoparticle release was monitored under real-world operating conditions, in one thermal spraying and one tile firing facility. INPs monitoring has been carried out at the emission source (ES) and in the worker area (WA). Nanoparticles were characterised in terms of particle mass concentration, particle number concentrations and size distributions. Size-resolved aerosol chemical composition was carried out by collecting samples on polycarbonate filters using ELPI+ and PTFE filters using SKC PCIS cascade impactors, followed by acid digestion and analysis by ICP-MS and ICP-OES. Particle morphology was assessed by SEM-EDX. The mean particle number concentrations (C) and size (S) were calculated in the ES and WA (Table 1). It should be noted that the data in the WA refer to full-shift averages. The high concentrations evidenced the need to implement mitigation techniques, given that the mean concentrations in the WA exceeded the NRV: 4·104 NP/cm3. Table 1. Mean particle number concentrations and sizes monitored in the ES and in the WA (NanoScan monitor (20-420 nm)). ============== ========= ======== ======== ========= Industrial activity ES C ES S WA C WA S ============== ========= ======== ======== ========= HVOF 9.75E+06 40 6.82E+04 49 APS 4.47E+06 55 6.11E+04 50 Tile Firing 3.14E+05 44 2.51E+05 57 ============= =========== ========= ======= ======== C:NP/cm3 S:nm The chemical composition analysis showed the influence of characteristic tracers of the processes evaluated. Particle morphology was variable as a function of the emission sources, with relatively spherical particles, as well as irregular ones and aggregates.