Physicochemical and Toxicological Characterizations of Laser Printer Emissions.

Sandra Pirela, Georgios Pyrgiotakis, Georgios Sotiriou, Philip Demokritou

There is evidence associating the use of laser printers and emission of PM, ozone and VOCs. Recently, there have been concerns associated with the incorporation of engineered nanomaterials into toner formulations to improve quality but the implications on exposures are unknown. In this study, a realistic exposure system was developed to generate exposure atmospheres associated with commonly used laser printers. The printers were placed in a controlled environmental chamber and their emissions monitored during a continuous print job lasting 60 minutes. Real time instrumentation was used to measure emitted particle number concentration, size distribution, mass concentration, ozone, carbon dioxide, carbon monoxide levels, relative humidity and temperature. The effect of various operational parameters, such as warm-up period, drum temperature and page coverage, on the emission profile was investigated. The printers were then ranked based on their emission profiles and the 3 highest emitters underwent further physico-chemical and morphological analysis. Emitted PM was sampled and size-fractionated using the Harvard Compact Cascade Impactor. Morphological examination of the laser printer emissions and toner powder was performed using TEM. Surface chemistry was assessed using EDS. Furthermore, the collected PM was then extracted from the impaction substrates and stabilized in deionized water, followed by characterization for hydrodynamic diameter and zeta potential via DLS. Chemical evaluation included SF-ICP-MS, GC/MS, and organic and elemental carbon analysis. An in vitro toxicological evaluation was done to investigate the biological response of various cell lines to the collected PM. Results show peak emissions to be model-dependent and varied between 3,000 to 1,200,000 particles/cm^3 with modal diameters ranging from 49 to 208 nm. Preliminary toxicological data showed that laser printer emissions may induce biological responses, such as increased pro-inflammatory cytokines and decreased cell viability. These results suggest that printer-emitted particles may be deleterious to lungs of those exposed to them.