Experimental determination of deposition of diesel exhaust particles in the human respiratory tract

Abstract

a b s t r a c tDiesel emissions are a major contributor to combustion-generated airborne ambient particles. To understand the role of diesel particulate emissions on health effects, it is important to predict the actual particulate dose deposited in the human respiratory tract, with respect to number, surface area and mass. This is complicated by the agglomerate nature of some of these particles. In this study the respiratory tract deposition fraction in the size range 10-500 nm, was determined for 10 healthy volunteers during both idling and transient engine running conditions of a heavy duty diesel engine. The aerosol was characterized with respect to both chemical and physical properties including size resolved particle effective density. The dominating part of the emitted particles had an agglomerate structure. For those formed during transient running conditions, the relationship between particle mass and mobility diameter could be described by a power law function. This was not the case during idling, most likely because of volatile compounds condensing on the agglomerates. The respiratory tract particle deposition revealed large intra-subject variability with some subjects receiving a dose that was twice as high as that of others, when exposed to the same particle concentration. Associations were found between total deposited fractions (TDF), and breathing pattern. There was a difference between the idling and transient cycle with TDF being higher with respect to number during idling. The measured size-dependent deposition fraction of the agglomerated exhaust particles from both running conditions was nearly identical and closely resembled that of spherical hydrophobic particles, if plotted as a function of mobility diameter. Thus, for the size range covered, the mobility diameter could well describe the diameter-dependent particle respiratory tract deposition probability, regardless of the agglomeration state of the particles. Whilst mobility diameter well describes the deposition fraction, more information about particle characteristics is needed to convert this to volume equivalent diameter or estimate dose with respect to surface area or mass. A methodology is presented and applied to calculate deposited dose by surface area and mass of agglomerated particles. The methodology may be useful in similar studies estimating dose to the lung, deposition onto cell cultures and in animal studies.

A Set-up for Respiratory Tract Deposition Efficiency Measurements (15-5000 nm) and First Results for a Group of Children and Adults

“…The set-up used for the respiratory tract deposition measurements was an improved version of a set-up described in several previous publications (e.g., Löndahl et al, 2006;Rissler et al, 2012), and followed the general experimental guidelines described in Löndahl et al (2014). The new setup is referred to as RESPI 2 .…”

“…An SMPS classifies the particles according to their mobility diameter, d me (identical to the thermodynamic diameter). The mobility diameter is related to the diffusivity of the particles and has been proven to be the equivalent diameter that best describes the lung deposition for particles < 300 nm), regardless of particle shape or density (Heyder et al, 1986;Schmid et al, 2008;Rissler et al, 2012). Deposition by diffusion is governed by the particle diffusivity, D, which is related to mobility diameter as 1/d me .…”

“…Eq. (1) was based on Rissler et al (2012), with minor modifications. The equation was fitted to the DF(d p ) curves of each subject by using a least square approach.…”

Size-Resolved Respiratory Tract Deposition of Sub-Micrometer Aerosol Particles in a Residential Area with Wintertime Wood Combustion

“…The estimations of volume and surface area are based on the assumption of spherical particles. Since freshly emitted soot particles, in several studies, have been shown to be highly agglomerated and thus far from spherical (Park et al, 2003;Rissler et al, 2012) such assumption could result in a severe overestimation of the deposited particulate volume and an underestimation of surface area when calculated from mobility number size distributions (as measured by a mobility particle sizer type of particle number size distribution instrument) . However, in the case of the particles found in Lycksele during the campaign there are several factors that indicates that the assumption of spherical particles is the best assumption to be made.…”

Nanoparticle pollution and associated increasing potential risks on environment and human health: a case study of China

“…1 Potential exposure risk in manufactured nanoparticle (MNP) process through a typical life cycle adapted from Thomas et al (2009) An important source of PM 2.5 is from diesel exhaust, which is a complex mixture of hundreds of constituents in either gas or particle form (Wichmann 2007). The diesel exhaust typically mainly consist of carbon and absorbed organic compounds and other metals and trace elements, thus they are highly respirable and have a large surface area (Risslera et al 2012). The diesel exhaust particles entering the respiratory tract would be a risk factor for the development of diseases of the respiratory system (Yoshizaki et al 2015).…”