Multiparametric approach as a tool for the evaluation of nanoparticles emissions from laser printers in the professional exposure assessment

Recently published studies focused on potential sources of indoor unintentionally formed nanoparticles (NPs), e.g. from combustion processes, have evidenced that laser printers and photocopiers release, during the heating in printing processes, substances that represent a human health hazard. Generally, the evaluation of occupational exposure to NPs in workplaces needs dimensional and chemical characterization. However, the main problem is linked to the choice of the appropriate sampling and dimensional separation techniques. Therefore, a convenient multiparametric approach to improve the knowledge on NPs exposure from laser printers is characterized by the contemporary use of different sampling, measuring and chemical analysis instrumentations. In the present work, as the study performed on a single predominant source allows to overcome the problems connected with the simultaneous contributions of different and time dependent sources, for the evaluation of professional exposure to NP preliminary results of emissions from isolated laser printers (different in brands and in toner‘s age), obtained by measures performed in an experimental box-chamber, are reported and discussed. In particular, in order to combine chemical and dimensional results, the experimental design has included: size-resolved characterization measurements (by a Fast Mobility Particle Sizer -FMPS) and the chemical characterization, obtained on size-segregated particles collected by multistage cascade impactor (NanoMoudi 122R), was performed by an Inductively Plasma Mass Spectrometer (ICP- MS) and a Gas-Chromatography Mass (GC-MS) respectively for the detection of metal ions (by which toners are charged) and Volatile Organic Compounds (VOCs) and Semi-Volatile Organic Compounds (SVOCs). Size segregated samples were also analysed by Scanning Electron Microscope (SEM) in order to correlate the obtained chemical results with morphological information (e.g. relating the formation of aggregates and/or agglomerates of NPs). Furthermore, fluctuations of ozone and VOCs concentrations inside the experimental box during the printing process, were detected by a photometric gas analyzer (Thermo Environmental Instrument 49C Ozone Analyzer) and a photoionization detector (PID) (MultiRae IR-Multi-GAS MONITOR PGM-54) respectively, whilst changes in temperature and humidity were checked by a microclimatic control instrumentation (BABUC). The standardisation of the multiparametric approach proposed can represent a valid support for the overall characterization of particles emitted from specific sources (such as laser printers) and for the arrangement of appropriate prevention and protection interventions which fulfill high standards of occupational health and safety of workers. Furthermore, the results obtained by the application of this approach can be considered a useful tool for the definition of Occupational Exposure Limit Values for NPs and, for this purpose, future efforts should be directed to study the complementary of different kinds of measurements.