Characterization and Quantification of Ultrafine Particles and Carbonaceous Components from Occupational Exposures to Diesel Particulate Matter in Selected Workplaces

Abstract

Questions still exist regarding which indicator better estimates worker’s exposure to diesel particulate matter (DPM) and, especially for ultrafine particles (UFP), how exposure levels and the characteristics of the particles vary in workplaces with different exposure conditions. This study aimed to quantify and characterize DPM exposures in three workplaces with different exposure levels: an underground mine, a subway tunnel, and a truck repair workshop. The same sampling strategy was used and included measurements of the particle number concentration (PNC), mass concentration, size distribution, transmission electron microscopy (TEM), and the characterization of carbonaceous fractions. The highest geometric means (GMs) of PNC and elemental carbon (EC) were measured in the mine [134 000 (geometric standard deviation, GSD = 1.5) particles cm−3 and 125 (GSD = 2.1) µg m−3], followed by the tunnel [32 800 (GSD = 1.7) particles cm−3 and 24.7 (GSD = 2.4) µg m−3], and the truck workshop [22 700 (GSD = 1.3) particles cm−3 and 2.7 (GSD = 2.4) µg m−3]. This gradient of exposure was also observed for total carbon (TC) and particulate matter. The TC/EC ratio was 1.4 in the mine, 2.5 in the tunnel and 8.7 in the workshop, indicating important organic carbon interference in the non-mining workplaces. EC and PNC were strongly correlated in the tunnel (r = 0.85; P < 0.01) and the workshop (r = 0.91; P < 0.001), but a moderate correlation was observed in the mine (r = 0.57; P < 0.05). Results from TEM showed individual carbon spheres between 10 and 56.5 nm organized in agglomerates, while results from the size distribution profiles showed bimodal distributions with a larger accumulation mode in the mine (93 nm) compared with the tunnel (39 nm) and the truck workshop (34 nm). In conclusion, the composition of the carbonaceous fraction varies according to the workplace, and can interfere with DPM estimation when TC is used as indicator. Also, the dominance of particles <100 nm in all workplaces, the high levels of PNC measured and the good correlation with EC suggest that UFP exposures should receive more attention on occupational routine measurements and regulations.

3D Imaging of Roadside and Underground Railway Particulate Matter Structures

“…In this study, confocal microscopy was successfully applied to investigate the structure, size, and appearance of particulate matter (PM) collected beside a busy London road as well as two platforms at a London underground railway station. It has been previously shown that the composition of PM changes between types of workplace . The jagged nature of some particles may not be clear on 2D imaging alone which may explain why some SEM studies have suggested roadside particles may have a more spherical appearance; nevertheless, our SEM imaging of underground railway station PM was consistent with confocal microscopy in showing that some particles can have sharp appearing edges.…”

“…It has been previously shown that the composition of PM changes between types of workplace. 17 The jagged nature of some particles may not be clear on 2D imaging alone which may explain why some SEM studies have suggested roadside particles may have a more spherical appearance; 13 nevertheless, our SEM imaging of underground railway station PM was consistent with confocal microscopy in showing that some particles can have sharp appearing edges. The geometries of microparticles have previously been shown to affect interaction with cancer cells; 18 in that study, microparticles were found not to enter cells if the surface in contact was round, whereas sharp particles could attach to cells.…”

Characteristics of Occupational Exposure to Diesel Engine Exhaust for Shipyard Transporter Signal Workers

“…In December 2018, the European Union adopted a legal OEL of 50 µg/m 3 for EC; the regulation will take effect in 2026 in underground mines and tunnel construction and in 2023 in other industries. CAREX Canada recently set a recommended OEL of 20 µg/m 3 for EC in mining and 5 µg/m 3 in other industries [15,30,31]. In this study, the mean exposure level in all signal workers was 4.16 µg/m 3 , which corresponds to a low exposure group that includes truck, bus, or taxi drivers and household-waste collectors.…”

Environmental and Occupational Short-Term Exposure to Airborne Particles and FEV1 and FVC in Healthy Adults: A Systematic Review and Meta-Analysis

“…Such exposures can occur while commuting [22], performing physical activity near a high traffic route [23][24][25], during episodes of high daily average concentrations of fine and ultrafine particles [26,27], and in microenvironments near transport hubs, roadways, underground train stations, and industrial sites [28][29][30][31]. In addition, millions of workers worldwide are daily exposed to processes and tasks associated with the emission of particles at concentrations higher than the typical urban background, such as welding fumes, forest fires, wood dust, and diesel engine exhaust [32][33][34][35], which are known to contribute to mortality by respiratory outcomes [36,37].…”