An investigation into the use of < 38 µm fraction as a proxy for < 10 µm road dust particles

Abstract

It is well documented that a large portion of urban particulate matters is derived from road dust. Isolating particles of RD which are small enough to be inhaled, however, is a difficult process. In this study, it is shown for the first time that the\ 38 lm fraction of road dust particles can be used as a proxy for road dust particles \ 10 lm in bioaccessibility studies. This study probed similarities between the \ 10 and \ 38 lm fractions of urban road dust to show that the larger of the two can be used for analysis for which larger sample masses are required, as is the case with in vitro analysis. Road dust, initially segregated to size \ 38 lm using sieves, was again size segregated to \ 10 lm using water deposition. Both the original \ 38 lm and the separated \ 10 lm fractions were then subject to single particle analysis by SEM-EDX and bulk analysis by ICP-OES for its elemental composition. Dissolution tests in artificial lysosomal fluid, representative of lung fluid, were carried out on both samples to determine % bioaccessibility of selected potentially harmful elements and thus probe similarities/differences in in vitro behaviour between the two fractions. The separation technique achieved 94.3% of particles \ 10 lm in terms of number of particles (the original sample contained 90.4% as determined by SEM-EDX). Acid-soluble metal concentration results indicated differences between the samples. However, when manipulated to negate the input of Si, SEM-EDX data showed general similarities in metal concentrations. Dissolution testing results indicated similar behaviour between the two samples in a simulated biological fluid.

Simulated biological fluids – a systematic review of their biological relevance and use in relation to inhalation toxicology of particles and fibres

“…ALF has since been slightly modified compositionally to test a variety of materials such as stainless steels (Herting et al 2007), alloys (Hedberg et al 2010), and occupational dust (Witt et al 2014;Brown et al 2019;Figueroa-Lara et al 2019). A study on stainless steel alloys determined preferential leaching of Fe followed by Ni and Cr, primarily in the first hour of immersion in ALF (Herting et al 2008).…”