ULTRAFINE PARTICLES IN WORKING ENVIRONMENT AND AMBIENT AIR: REAL-TIME MEASUREMENTS, CHARACTERIZATION AND EVALUATION OF EXPOSURE ROUTES

Ultrafine particles (UFPs) are released in ambient air from natural and anthropogenic sources but also certain workplace conditions are responsible for the unintentional emission of this kind of particles. The small size and corresponding large specific surface area of UFPs and nanoparticles (NPs) are responsible for the great biological activity per given mass. Other specific characteristics of UFPs such as number concentration, shape, agglomeration state and chemical composition play an important role in determining toxicity and reactivity. Even though UFPs represent a major concern in terms of human exposure, excluding some guidelines for workplace air currently there is no legal threshold for controlling them in ambient air. The aim of this thesis is to measure and characterize UFPs that can be found in working environments and ambient air and, afterwards, explore possible exposure routes. UFPs emission from three kinds of industrial processes were investigated in real working conditions by means of real-time measurements of number concentration and size, morpho-chemical characterization and quantitative analysis of metals in airborne and deposited particles. We demonstrated that iron/manganese oxide nanoparticles are the most representative particles released during automatic gas tungsten arc welding (GTAW) of steel. Moreover, despite the respect of the American Conference of Governmental Industrial Hygienists (ACGIH) limits for respirable aluminium, we found that oxy-fuel welding and the die casting production cycle of aluminium-based products involve the release of UFPs with a chemical composition consistent with the raw materials. From our findings, surface and skin contamination seems to be a secondary source of exposure to UFPs, suggesting a possible increased risk in workers mainly for inhalation exposure. Regarding the evaluation of the presence of UFPs in ambient air, a study was performed in proximity of an industrial “hot spot” in Servola district in Trieste where an integral cycle steel plant is located. Particle number concentration (PNC) in the range 10-300 nm in “Servola” site was about two times higher than “background” values. Moreover, an increase of PNC corresponding to a decrease of the particle size and vice versa was observed. In the particulate matter, agglomerates of nanoparticles containing Fe, Zn and Mn were observed by means of a transmission electron microscope coupled with an energy-dispersive X-ray analytical system (TEM-EDS). The contribution of Fe concentration in the PM1 and, in particular, in the particle fraction below 250 nm seems to be not negligible. This result is highly significant from a toxicological point of view. Servola district is densely inhabited and people live very close to the integrated steel plant that is a relevant emission source. Afterwards, nanoparticles compatible with those found in the aforementioned studies were tested in vitro using the method of static Franz diffusion cells in order to explore possible exposure routes. In particular, dermal and meningeal absorption of Al2O3NPs and MnFe2O4NPs respectively were investigated leaning, in both cases, towards a reassuring absorption profile in physiological conditions.