Abstract
A fluidized bed aerosol generator was connected to a 13-stage cascade impactor (nanoMOUDI) for the size fractionation of urban dust (<10 µm), followed by the gravimetric analysis of loaded PTFE filter samples. This method was used to characterize the PM10 (thoracic) fraction of road dust sampled from expressways, arterial roads and local roads in Toronto, Canada. The fine particle fractions (<1.8 µm) of all the studied samples accounted for 51–72% of the resuspended PM10 (by weight). Elemental analysis using ICP-MS and ICP-OES revealed an overall trend of element enrichment in the <1.8 µm fraction compared to the coarse fraction (1.8–10 µm) of the road dust. By contrast, archived house dust samples displayed the reverse trend for most elements. The lung bioaccessibility of target elements (Al, B, Ba, Co, Cr, Fe, La, Mn, Mo, Sb, Sr, Ti, V and Zn) was assessed for each road dust fraction using 0.1 M ammonium citrate (pH 4.4) to simulate intracellular fluid and Gamble solution (pH 7.2) to simulate interstitial lung fluid. The <1.8 µm fraction of local road dust displayed significantly higher bioaccessibility (p < 0.05) for Zn when using Gamble solution, and for seven out of the 14 target elements when using ammonium citrate. These results show the importance of characterizing the fine fraction of road dust.
Highlights
The health impacts of exposure to airborne particulate matter (PM) can include an increased risk of respiratory problems, cardiovascular effects and cancers [1,2]
A comparison of the relative proportions of fine particles (PMfine) versus coarse particles (PMcoarse) can be derived from Figure 1, by combining the wt% values for the ten fine fractions (1.8 to
This study addressed the need for a relevant methodology for isolating and sizefractionating urban dust particles within the thoracic fraction (
Summary
The health impacts of exposure to airborne particulate matter (PM) can include an increased risk of respiratory problems (e.g., dyspnea, asthma and chronic bronchitis), cardiovascular effects (e.g., vascular inflammation and atherosclerosis) and cancers [1,2]. A relatively new area of interest in the field of public health is the impact of resuspended road dust on human health, on the respiratory and cardiovascular systems [6]. Road dust is a complex medium that is generated by the accumulation of particles derived mainly from vehicular exhaust and nonexhaust sources (particles emitted from tire and brake wear, road surface erosion and urban soil) [7]. Due to the turbulence created by road transportation and wind, resuspended road dust is recognized to be an important source of atmospheric PM, in large urban centres [8,9]. Particular concerns have been raised about inhalation exposures to vehicular sources of transition metals (e.g., Zn, Mn and Cu), which generate reactive oxygen species (ROS) [12,13] and which tend to display high bioaccessibility in the respiratory tract [5]
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